What To Do To Change The Tooth Patern On A 8.8 Ford Rear End

Hi All, (warning long postal service......)
I recently ran into a gear whine issue when I had a set of Ford Functioning three.73" gears replaced w\ a gear up of Richmond EXCEL iii.89" gears in my Stang. The shop manager that did the piece of work is a very experienced guy that knows how to properly gear up gears (as well as myself) & he knew the gears were whining before I picked upward my car (he told me so up forepart too) just he couldn't figure out why (he also told me up forepart that he would adopt me to use Ford Performance four.10 gears instead but I insisted using these Richmond gears thus understand the adventure of potential gear whine).

Then you now know the context upwards forepart.

I have read so many accounts of folks maxim that Richmond (or Motive, or Usa Gear, etc) gears always whine....also certain Ford OE & Ford Performance gears e'er whine....and so information technology's always the gears are bad, rinse, repeat, etc.

And so I decided to research this issue as I believed that at that place was more to this than simply a lot of references\speculation to specific brand names & a person's knowledge level\competence level in gear setup....what I found out is that, associated w\ the Ford 8.8" axle's appearance, Ford too introduced a new gear tooth cutting procedure (ii-cutting face hobbed procedure....is used to make all current Ford 8.8" OE\Ford Operation gear sets) to make the gear sets for this beam that is unlike geometrically from the prior 5-cut confront milled process Ford used due west\ the Ford OE 9" axles (all the aftermarket gear manuf's however use this 5-cut confront milled process to make all electric current Ford-specific 8.8" gear sets) that gives a different pattern checking migration direction & tooth placement position when using gear marking compound to check the same pinion depth\backlash setting procedures used to align the pinion gear teeth chord line to the ring gear teeth chord line (or center if preferred) to achieve proper tooth contact thus mesh quietly under performance (no whining).

And then, unless a person knows which blazon of gear cutting procedure was used on a particular prepare of gears being installed in the Ford 8.8" beam in item, to then know which pattern checking migration & tooth placement position parameters to use west\ marker compound to properly gauge the pinion depth\backlash settings being applied, information technology will be very easy to make setup mistakes likewise as being very difficult\frustrating to set up them upwards (recall of a busted clock getting the time right 2 times a twenty-four hour period scenario.....you'll eventually get there but not w\o a lot of effort & confusion) due to which type gear cut blueprint you got used to setting upwardly 1st prior to handling the 2nd blazon. With the Ford 9" axles this isn't an issue as all Ford ix" gear sets whether OE or aftermarket are fabricated using the same five-cut face milled gear cut process so at that place is no pattern checking parameter differences to account for.....thus much easier & simpler to do. This has been the instance until recently when US Gear (Moser) has started making Ford 9" gear sets using the newer 2-cut face hobbed procedure instead of the older 5-cut face milled process so all you Ford 9" users be warned.............

The cause is and so an identification result due west\ the Ford 8.8" axle of how to recognize which blazon of gear cutting procedure yous're looking at to then know which checking pattern to apply to properly interpret the pinion depth\backfire setting movements to properly align the pinion depth\backlash to properly middle the pinion to the ring gear to hit the pinion gear\band gear chord lines so they mesh right thus non whine!

This is the reason why most skilful shops volition accept either the loftier dollar, very authentic pinion depth setting tool (this tool eliminates the gear tooth cut process being a factor in setting the pinion depth.....but the only way it gets you out of the checking pattern issue is if you hitting the pinion checking number exactly or within the gear manuf's recommended variation window used to eye the pinion gear to the band gear during QA\QC prior sale) and\or they know how to ID which gear tooth cut process they're working with to then know which design checking parameters to use when setting the pinion depth\backlash.

So from checking this forum & finding nothing to help all united states of america DIY'ers to know\be enlightened of this concerning the Ford viii.eight" axle, hither is a link provided to a very skilful article that explains this due west\ very good pictures of these differences showing the blueprint migrations from center for both processes when setting pinion depth (called PMD or pinion mounting altitude....same thing) or backlash afterwards correct pinion depth is achieved : DIY Ford - Ford Axle Ring and Pinion Assembly How to Guide besides as provided below a .pdf of a Dana Gear Type Interpretation Chart that shows how to ID which type of gear cut process (whether 5-cutting face milled or 2-cut face hobbed) was used to make the gears as well equally the associated pattern checking parameters to use for both processes so this is not brand dependent (by now I believe most OE gears are being cut using the newer 2-cut face up hobbed dry procedure which is much faster & simpler thus cheaper to make a gear gear up with than the older 5-cutting face milled wet process simply most aftermarket manuf's can't afford the expense of a consummate equipment swapout to change over based on their existing turn a profit margins and then they continue to use the old 5-cut face milled process w\ their Ford 8.8" gears that they sell.....).

When I showed all this to the store manager that prepare my gears, he admitted that he didn't know this was a affair (I admit I didn't either until I did all the inquiry)....he was e'er setting up Ford Functioning 8.8" gears (his preference & sets them using the sometime school setting procedures....) and then he had unknowingly gotten used to looking at a 2-cut confront hobbed process thus gotten familiar w\ the associated blueprint checking parameters for a ii-cut face hobbed gear set. The Richmond gears (aftermarket) were cut using the older 5-cutting face milled process (but assumed that all gear sets are made the aforementioned fashion.....audio familiar?) which the pattern checking parameters he was accustomed to using west\ the Ford Performance gear sets (two-cut confront hobbed) won't respond the same way w\ this Richmond gear fix (5-cut face milled).....so he made elementary interpretation mistakes due to natural (not willful) ignorance which acquired him a lot of headaches trying to get them correct (took over 4 days) & still got them wrong in the end (whining).

1 of my strengths in the profession that I worked in earlier retirement (Production Specialist for a major oil company) was ability to perform solid & accurate root cause\effect analysis to effectively solve operational issues............IOW's, fixing broke stuff.

When we got together in person & I showed him the proper pattern checking parameters for a v-cut face milled gear set (Richmond is an aftermarket gear....1st clue) & used it to compare w\ the pictures of the last gear setting compound design markings he sent me, he chop-chop then recognized that somehow he had lucked out & got the pinion depth set correct (the part that takes the longest time & effort to get right w\o using a pinion depth setting tool) thru a lot of excess time wasted (which I paid for) just had ready the final backlash mode as well loose from trying to friction match upwardly the pattern shape on both the drive\coast sides from using the wrong two-cut face hobbed pattern checking parameters which put the pinion molar chord line high heel on both drive & coast side thus completely off the chord line (true heart of teeth or ease-off if yous prefer) of the band gear teeth thus whining on both accel\decel....not because he didn't know HOW TO Set up GEARS or the Brand of gear set used, he didn't know the bodily gear tooth cut procedure used w\ the bodily gear set he was working with to and then know which pattern checking parameters to use to guide him properly west\ their setup!

So in the end I get a free fix as from the proper comparison using the proper checking parameters that matched the gear fix's tooth cutting procedure in question all we need to do in the stop is to only reset the terminal backlash to the manuf'southward recommended backlash variation range (nosotros're gonna shoot for the tighter side of the range on purpose) to make it all line up correct & I got a big thank yous from the shop managing director for taking the fourth dimension to work w\ him in a respectful mode to help him to learn something he didn't know\was unaware of that will assistance him out going forwards (I gave him all of the research materials I had printed out in a packet to have so he could refer back to all this on future jobs) & not being a dick client blaming him\degrading him for his "lack" of competence in doing his piece of work.

I'll wager this is a MUCH, MUCH more common issue (on both sides of the aisle) than well-nigh would admit concerning setting up gears in the Ford 8.8" axles....

Hope this helps.
Attached Files:
Final edited: November 12, 2021
Here is provided a link to an article that explains all the relevant geometrical differences betwixt the 2 gear molar cut processes for all those and so inclined: Face-off: Face up Hobbing vs. Face Milling | Gear Solutions Magazine Your Resource to the Gear Industry
Relish!

PS-- Also as a piece of communication, don't always count on the gear manuf's setting directions to properly guide you lot equally they are sometimes entirely too generic & lack detail (vague) or leave out needed data that you need to know. The Richmond EXCEL gear installation instructions....while designed for this gear gear up series doesn't mention anything about a Ford 8.8" axle....merely Ford viii"\nine" axles....so can easily exist misinterpreted (the Ford 9" & Ford 8.8" axles use dissimilar gear cut processes to brand their gear sets) & doesn't mention anything well-nigh setting pinion depth exterior of using a pinion depth setting tool to apply the pinion checking altitude numbers to set pinion depth.

So in Richmond's case, they demand to revamp all their installation instructions to CLEARLY reflect the differences w\ Ford viii.8" & Ford ix" gear sets so folks won't make these simple only plush mistakes.

Last edited: Nov 12, 2021
Cheers for the write up. This explains some perplexing issues I've had with some past setups.
Wow! This perfectly explains why I wasn't getting the contact blueprint I was looking for when I set up upward my unequal with the 3:73'due south. I fussed with that matter for several hours with it in the car, then finally removed the unabridged axle, put information technology on the bench to fix it up, then fussed over information technology for another 4 hours or more. Thanks so much, GlassTop09, for this gilded info. The veil has been lifted......
RED09GT Equal Opportunity Offender S197 Team Member

That'southward a great read. I had observed the divergence in tooth height but did non know that it basically reverses the steps for correcting the pattern or the name of the procedure.
First fix of gears I did was a fix of Richmond 3.73'due south in my fox body and used a set of generic set upwardly pictures from an old chilton all makes repair manual and they were quiet- but did have a change in pitch from the iii.08 gears.

When I did my Ford Racing 4.10'southward in my auto, I gear up it upwardly like a face milled gear up, measured the pinion depth, etc... and shimmed the pinion to correct what I idea was the pinion being besides shallow on the coast side. I played with it to attempt and become a decent pattern and settled with a thicker pinion shim than stock. They whined on deceleration.

I later put the 3.55'southward back in due to the internet telling me that three.55's would exist better for a turbo car (perchance with an auto and a torque coverter that the motor overpowers, but not the case with a TR6060 and a heavy street car).

When I put the 4.10's back in, I re-used my thinner shim that came with the manufactory iii.55's, then adjusted backlash until information technology had a decent design and they are now placidity.

I had no thought why and causeless that I didn't get the measurements and calculations correct. Now I observe out it was considering I was trying to gear up a confront hobbed gearset using a face milled method.
Thanks for the new piece of knowledge!
+one on the neat info! I did not know this either, simply always 'preferred' to do FRPP gears just because of the ease of installation and about of the time coming out quiet (with appropriate backlash).
Later on reading the deviation in prepare procedures I will revisit my differential this wintertime. Maybe I can get the 4.30s to run quietly.
This is the problem w\ using other generic pattern checking parameters from all the different manuf's w\ the Ford 7.5" & eight.8" axles......yous don't know which gear cutting process they're referencing to as they don't tell you & none of them are consequent in presentation.....even Ford Performance doesn't say just they do requite you the proper pattern checking parameters that matches the 2-cut face hobbed cut process used to brand the gears in their .pdf's.
It is this 2-cut face hobbed process & Ford's use of the MHD (chief housing dimension) blueprint for the 7.5"\viii.8" beam housing (the four.415" std altitude from carrier beam centerline to shim side of the pinion head gear) that makes the appearance of using the aforementioned pinion shim thickness w\ the original Ford OE or FP gear set installed in a housing for each post-obit Ford OE\FP gear set installed in same housing....even if dissimilar ratios upwards to the four.56:1 gears.... So this is by design by Ford w\ the vii.five"\viii.8" axles........
Here's an article on this:
SSOTN - Gear Install (superstallions.com)

Dana\Spicer Gear is the only one I establish who fabricated a .pdf specifically devoted to ID'ing the two types of gear cutting processes & giving the full design checking parameters for both processes....thus can be printed out & kept in a binder to use w\ all other manuf's Ford 7.5"\8.eight" specific gear sets.

Last edited: Nov 17, 2021
I tin tell you I have done many sets of gears over the years. I know a lot of shops that would not do a iii:90 Ratio for the viii.eight because of the aggravation while doing them and afterwards with customer concerns.
Yeah, I kept that in listen as well. During all my enquiry, when I read that DIY Ford article down towards the stop of it when the author started caption of gear ratios falling into "not hunting" or "semi hunting" or "full hunting" (which has to do w\ the pinion gear\ring gear tooth count ratio to determine the corporeality of revs a pinion gear tooth would take to make to realign west\ the same ring gear tooth grouping every bit if this happens within a certain # of revs of the gear set the band gear teeth volition have concentric contact wear patterns that volition be in harmony thus emit a specific resonance pattern (or noise) every bit the specific pinion gear teeth rotate thru them.
So this event is what makes the iii.89 ratio (ix tooth pinion\35 tooth ring) somewhat suspect as the very next ratio (iv.00:1....uses a 9 tooth pinion\36 tooth ring ratio which is a mutual cistron gear set w\ no prime which is a not-hunting gear...needs to accept timing marks cut on pinion gear & ring gear to force the gears to "hunt" & thus stop the resonance consequence) thus makes this specific 3.89 ratio-even though the ratio is not a common cistron Only also a non prime number gear set-a semi hunting gear gear up (means that the same thing can happen as w\ a non hunting gear set merely information technology takes a few more revs than a non hunting gear gear up to practice it) but most gear manuf's won't cut timing marks on these type of gear sets thus the hit\miss issue westward\ resonance due to a gear molar timing pattern result.

The gears that are the quietest are full hunting gear sets (these type ratios takes many, many revs to occur for the same teeth patterns to realign thus don't become tooth article of clothing that autumn into a resonance emitting pattern).

They are ordinarily distinguished by the pinion gear tooth count being a ii-digit number & none common factor w\ a prime number for both pinion & ring gear (no divisor).

And then if a iii.ninety gear fix is desired, get the three.91 ratio gear set up (uses a xi pinion molar\43 band tooth count ratio) instead of the 3.89 ratio gear set up.

My issue is that I didn't know this either until after I bought my gears (had them for over a year before install). Richmond usually follows the Ford OE gear pattern (note the three.89 ratio is a Ford OE design for the Ford 9" axle) thus made this for the Ford 8.8" axle also (ring gear dia was close enough to accommodate this ratio). At present the other aftermarket gear manuf's utilise the three.91 ratio instead of the 3.89 ratio for this eight.8" axle.....my read is due to the semi hunting nature of the 3.89 tooth count ratio.

1 of the side effects of our beloved S197 chassis.....due to it'due south much improved chassis stiffening....is it is likewise very susceptible to cabin resonance (why certain exhaust resonance volition easily dilate into droning) & when yous install stiffer LCA's\UCA'due south or certain 1-piece driveshafts that employ U-joints on each end attached to this 8.8" rear axle yous increase the risk of cabin resonance (also associated due west\ gear whining even though the gears are properly centered) from a semi hunting\non hunting gear gear up installed in this eight.8" axle (one of the reasons why this chassis was designed w\ the infamous 2-slice DS w\ those 2 CV joints...merely the DS section between these 2 CV joints is filled w\ a resonance reducing textile so the combination of the 2 CV joints (constant load which do not emit a resonance like U-joints when past the 3* angle off) coupled west\ the resonance boring section betwixt the 2 CV joints effectively cancel some gear set resonance thus prevents motel amplification of it. This I also did not know.....until now during my research. I made a video of this demonstrating this resonance deadening west\ my OEM 2-piece DS............

And so since I still have my car's original 2-piece DS & all hardware to reinstall it, depending on the effect of my reset & knowing all this at present concerning this 3.89 gear ratio'south semi hunting nature I may exist reinstalling this 2-slice DS to stop killing this (I accept the Ford Racing i-piece Aluminum DS west\ 2 Spicer 1350 U-joints installed currently....you can clearly hear this DS get a big megaphone which amplifies into the cabin) cause at this time information technology'southward a "free" gear up & since my goals for this machine is at present mostly cruiser duty this is IMHO the logical adjacent step.

Hell of a fourth dimension to find all this out.....just since I'k blessed at the moment to be able to beget the costs of these lessons learned the hard way I count it all every bit a positive cause I learned something I didn't know earlier thus volition brand me a improve "DIY technician" going forwards & post all this hither to hopefully help others and so that they tin can avoid making these uncomplicated merely costly mistakes from simple lack of knowledge.

Last edited: Nov 18, 2021
I don't know what technique your installer used to set up the pinion depth simply Ford uses a set measurement from the large pinion begetting to the bottom of the side bearing saddle. Using their tool positioned, a shim is tried betwixt the tool and bottom of the tube in side begetting saddle until a slight drag is found. If you attempt to use a measurement from the top of the pinion crown they aren't machined for that propose then errors will occur. I used the Ford tool to install my 4:10's in my previous mustang and there was no noise from them at all. IMHO if a differential shop doesn't have the proper tooling to practice Ford rear ends or other manufacturers possibly they shouldn't be doing them. It's the price of doing business organisation and can but give them a bad name if they accept multiple failures from guessing or just reusing the original pinion shim. If you look at the FRPP installation instructions for the 8.8 it shows the special tool and pictures of the pieces with their dimensions for stacking together. I had a machinist I know make the tool for me every bit milling accurateness is needed to meet the specs. I didn't have the correct size tube for the side bearings so I used a smaller tube and shimmed under the caps to concur it in place.
Hi Lime1GT,
That Ford OE pinion depth setting tool you posted nearly won't work w\ an aftermarket set of gears.....it was specifically designed to work w\ Ford OE or Ford Performance gear sets but (as you have alluded to in your posting).
My postings here in this thread is concerning the difference betwixt 2 types of gear tooth cutting processes used by gear manuf's to brand gear sets for this Ford 8.8" axle when using the old fashioned gear marking compound to cheque pinion depth & backlash setting cause if you don't ID the blazon of gear cut to and so utilize the matching checking patterns y'all'll make the aforementioned mistakes & the same tin happen to whatever shop or private....not due to incompetence but simply lack of knowledge of these differences. Almost shop personnel don't get\go sent to formal trade schools (similar MIT for case) to get formally trained on this stuff and then tin can hands fall into this unknowingly......no thing how many years experience a person has.....it'due south virtually exposure, non experience.

It will depend on a person's grooming\background likewise equally the corporeality of exposure to both gear molar cutting processes & the hunting aspects to know nearly all this..........and then considering of this most shops since the appearance of the Ford 8.8" axle do\take refrain from installing gear sets....in particular aftermarket versions of certain gear ratios due to the expense of this pinion depth setting tool & in addition to this the advent of recognizing whether a particular gear ready ratio is non-hunting, semi-hunting or full hunting along westward\ very low profit margins. Ford OE & Ford Performance gear sets for this 8.8" are all full hunting ratios by design thus will come in sure ratios only (this has to do w\ the pinion gear & ring gear tooth count ratio used to come up upwards w\ the actual gear ratio number). Most gear whining problems are actually tied to this lack of molar hunting attribute.....the majority of these will be aftermarket gear sets equally almost volition non inscribe timing marks on the pinion gear\ring gear on gear ratios that are using pinion tooth\band tooth non-hunting or semi-hunting counts to realign the gears to the original teeth they were lapped with during assembly in the beam to prevent them from whining (essentially you're having to try to "relap" the gear set teeth again to each other during the break in process....due west\o any lapping chemical compound). This makes these type of gear sets very hit\miss when installing.....fifty-fifty if you practice go the pinion depth\backfire set properly.

Over again it's not about competence\incompetence.......it's about exposure to all this seemingly picayune known info.
FYI........
I got westward\ my installer to bank check this Richmond EXCEL 3.ninety (bodily 3.89) gear set up to come across if it is truly a non-hunting\semi-hunting gear set by putting timing marks on a pinion gear tooth & ring gear tooth beyond from each other, then rotate the ring gear ane revolution to come across how the marked pinion tooth would align itself (ix tooth pinion gear\ 35 molar ring gear).....it came within ane ring gear molar of full realignment (2 of the 3 band gear teeth were even so engaged to this pinion gear tooth which makes this 3.89 gear set a non-hunting set thus tends to be noisy) thus is why it usually has noise issues (in that location's no way to detect the original teeth they were lapped to at Richmond west\o actual timing marks applied to both the ring & pinion gear teeth to lucifer them upward during associates.....the effect and so is frequency output from mismatched tooth meshing....a buzzing blazon of noise--not a roaring\binding type which tin indicate improper pinion depth\backlash setting or bearing failure--that operates in much the same style as exhaust resonance does to cause droning).
The pinion preload was found still belongings the 25 in\lb rotational load for new bearings, bearings were rotating smoothen & clean so no pinion bearing issues. Same for carrier bearings so no issues. Pinion depth was constitute still centered thus no reason to mess w\ it so only reset carrier BL from .012" to .007" (Richmond BL spec is .007"-.009") & checked design...all was textbook centered for a face milled gear set and then buttoned her upward at that bespeak. Loaded the axle w\ some Lucas 85W-140 GL-5 spec dino oil & test drove. Whining was much less than before but still present.

Put her thru a 10 mi pause in procedure of 0-45 MPH stop & go, varying speed, low load driving w\ several figure 8's added in to piece of work the Tru-Trac'southward helical gears & movement gear oil down to the outer beam bearings besides & got some positive results as gear whining did start to lessen some (some of the noise was institute to actually come from the Tru-Trac while information technology was unloaded when going in direct line so more effigy 8's are needed to finish tuning the Tru-Trac's helical gears likewise as more than varying low speed stop & go interruption in driving to allow pinion\band gear teeth to "lap" themselves to each other once again so allow a 30-40 min cooldown in between sessions).

Time will tell if these will eventually quiet downwardly enough to become acceptable. So far, from this reset, there's some positive promise to work with.

So in closing, if 3.xc'due south are desired for a Ford viii.8" axle, recommend to go the actual iii.91 ratio gear ready (11 pinion tooth, 43 ring tooth, total hunting, face milled so quiet) & stay away from this 3.89 gear ratio set (9 pinion molar, 35 ring tooth OE Ford 9" pattern, non-hunting, face milled so noisy).
I accept to add, I just e'er heard of hunting vs non hunting ratios.
Non hunting: same teeth mesh over and over. The reason why this is of import is when you are installing a used set of gears, you desire the aforementioned teeth to match up after the 2d install. It would also matter with new gears if they were lapped in.
Example: iii.00 gears, 13/39, each tooth on the pinion will mesh with the same 3 ring gear teeth on each and every revolution.
Hunting: all teeth on both band and pinion will mesh at some point.
Example: any ratio that is not an even number.
Semi hunting, no idea, lol.
Disclaimer: I only glanced over Glasstop's mail service. lol
This is the way I take come to sympathise all this at present as follows:
Non-hunting:
1.) Ring\pinion tooth count have common whole number divisor factor (same whole number divisor for both ring\pinion gear tooth counts which makes it a fully timed gear set; example: 3.l ... 10 pinion\35 ring have common whole divisor of 5) & both are non prime numbers (prime numbers don't take a whole number divisor, say like 11) and then volition hitting the aforementioned tooth group pairings inside 1 ring gear revolution OR ii.) Band\pinion tooth count accept no common whole number divisor factor Merely both are not prime numbers either so each has a whole number divisor and then look for the closest pinion\ring divisor pairing to determine if not-hunting or semi-hunting (iii.89 .... 9 pinion\35 ring, both have divisors, pinion is 3, ring has either 5 or 7, closest divisor pairing is three to 5 so time spacing is likewise close then volition human action every bit non-hunting within 1 ring gear revolution. My test proved this to be true w\ the Richmond EXCEL 3.89 gears every bit marked pinion molar came back inside 1 tooth spacing off the marked ring gear tooth thru one band gear revolution). These need timing marks to align the lapped gear teeth pairings back to each other whenever they're taken autonomously\reassembled or gear noise\whine is doubtable regardless of beingness new or used or pinion depth\backlash settings.

Semi-hunting:
Ring\pinion tooth count do non have common whole number divisor factor, i side will exist a prime (thus no whole number divisor) but the other side volition not be a prime number thus will have a whole number divisor so will have timing just will take more than 1 ring gear revolution to line back up due to the other having no whole number divisor thus no timed pairing (4.10 .... x pinion\41 band, pinion has whole number divisor of either 2 or 5, ring is a prime number number then no whole number divisor and so pinion tooth will lucifer back up to same ring gear tooth pairing over more than 1 band gear revolution) OR equally laid out in #2 example under not-hunting merely the closest divisor pairings are far enough autonomously (two to 9 for example) to force the ring gear to have to make more than 1 revolution to get dorsum shut enough to remesh in time due west\ the pinion gear. These aren't as bad as non-hunting almost noise when taken apart\reassembled but are still susceptible to gear dissonance so timing marks on these volition assistance to marshal the lapped gear teeth pairings back to each other to foreclose inducing gear noise.

Full hunting:
Ring\pinion tooth count do not accept common whole number divisor factors AND both pinion\band tooth counts are prime number numbers so no whole number divisors so have many, many ring gear revolutions occurring for the same pinion tooth to come close to simply never really line back up due west\ the same ring gear tooth pairings it started out with during lapping so no timed tooth meshing occurs. These are the desired gears equally they are the quietest by far & allow for looser setup. (3.73 .... 11 pinion\41 ring, no whole number divisors of either pinion or ring so no exact timing pattern develops during lapping then no timing marks are needed when taken apart\reassembled whether new or used).

This is the chief advantage w\ Ford OE or Ford Performance 8.eight" gear sets vs aftermarket 8.8" gear sets outside of the gear tooth cut process used equally Ford will not cutting a non-hunting pinion\ring gear tooth count gear ratio for this 8.eight" beam .... just either semi-hunting or full hunting pinion\ring gear tooth count gear ratios. This is why westward\ Ford Performance there are just sure gear ratios they brand available.

In brusk, the pinion\ring gear tooth count that is used to make a sure gear ratio gear set is important to know to ensure that you're getting a quiet running, piece of cake to work with (total hunting) ready of gears .........

The 3.89 gear ratio's pinion\band gear tooth count is a Ford OE 9" pattern (Ford made several gear ratios for the ix" axles using non-hunting gear tooth counts in the past so they tried to non make the same mistake due west\ the viii.8" axle) so aftermarkets adopt this pattern to the Ford eight.8" because it's an OE Ford pattern thus the whining issues. Some aftermarkets take fixed this potential whining event (Motive Gear) past going to the eleven pinion\43 band gear tooth count pattern to come up up w\ the 3.91 gear ratio full hunting gear set .... and it is reflected in information technology's price (costs most $100.00 more than than the Richmond EXCEL 3.89 gear fix).

This is why I made the recommendation to go west\ the three.91 version of a 3.90 gear ready instead of the 3.89 version IF a 3.ninety gear gear up is desired.

I learned all this too late for this round but volition not make whatsoever of these mistakes anymore going forward as I now know fully what\how\why to look for & what\how to handle it. I know what needs to be done to set this 3.89 gear prepare just information technology's really non worth information technology (break it in as best y'all tin and so when changing out the gear oil, check BL to encounter if it has grown from original fix, if has then mark gear teeth & reset BL back to original setting to force gear teeth to lap more until they quiet upwards .... just if you've gone this far just swap out gear set west\ a known total hunting version, ready them upwards & call it a twenty-four hour period) then when the time comes to do this I'll have a set of Motive Gear's 3.91 ratio full hunting gears to install cause for a street use, not track use FBO NA 05-10 iv.6L-powered S197 I find that these iii.ninety'south IMHO are the all-time all around gear ratio to run as they fit my engine's TQ output bend to a T thru this Tremec 3650 tran's gear ratios on 26" dia tires so I don't regret going to 3.90'due south at all .... only regret getting this 3.89 ratio non-hunting version of three.90 instead of the three.91 ratio full hunting version. So later on I take these iii.89's thru full break in to evaluate any resonance improvement then I will pull my FP one-piece DS w\ the 2 Spicer 1350 U-joints (gear resonance turns this affair into a big megaphone) & reinstall my OEM 2-piece DS w\ the ii CV joints & resonance deadened DS section between the CV joints to see if it will fully arrest whatsoever left over frequency to terminate it from resonating into the cabin (ane of the reasons for this DS blueprint by Ford as I plant out later due to the stiffer S197 chassis being more susceptible to cabin resonance or drone if y'all prefer so anything that creates frequency\resonance fastened to this chassis can get amplified into the motel as a buzzing\droning type noise) since this is a "free set up" at this signal & for cruiser duty don't really need the ane-slice DS merely I'll go on it as a spare.

Well I've read, I've studied so thus learned all I need to know going forward so will not become trapped over again.
Here is a YouTube video of a rock crawler explaining issues concerning gear quality that I institute to have some creditability thus something else to look out for:
The Truth Almost 4x4 Gears - YouTube

PS--Due to this video, I'k gonna back off the Motive brand & instead go w\ the Nitro Gear brand. Nitro Gear gives you all this pertinent info on their gear sets up forepart on their web site (all use the 5-cut face milled process, all gear ratios made for the Ford 8.8" axles are cut using either semi-hunting or full-hunting pinion\ring gear tooth counts merely like Ford Performance does but Nitro actually gives the pinion\ring gear tooth counts info on every gear ratio they offer--they also make the 11 pinion\ 43 ring gear tooth count 3.91 ratio full-hunting Ford viii.8" gear set that I want & their installation instructions bear witness clear, distinctive actual gear compound checking patterns based on the 5-cut process) & as the YouTuber posted, I've yet to find a bad review posted anywhere on the Internet out of at to the lowest degree 20 review videos I've seen to appointment from ten dissimilar posters.

I've come to suspect going forward any gear ready that in their install instructions only says to apply a pinion depth setting tool to set pinion depth.........if they have to use this tool in that location's some other reason why they accept to be fix and so accurately thus stay abroad......

A big advantage w\ Nitro Gear that the others don't offer is that y'all can buy direct from them from their web site so tin alleviate a lot of the electric current supply chain issues going on.
Yep! The Yukon gears I installed in my 8.8 said Made in China right on them and they cost half agin every bit much as the Motive gears I replaced.
Here is a picture of a Ford viii.viii" gear gear up using face hobbed (2-cutting) gear teeth (my FP 3.73 gear set....upper prepare in moving picture) vs a Ford 8.viii" gear set using face milled (5-cut) gear teeth (my new Motive 3.91 gear set....lower set up in picture) westward\ both gear sets being a full hunting type (FP iii.73 @ xi pinion\41 band tooth count.......Motive iii.91 @ xi pinion\43 band tooth count......both pinion\ring gear tooth counts are prime numbers--no whole number divisors thus no mutual divisor factor between the 2) and then no timed specific molar pairings occur between ring & pinion teeth during 1 band gear revolution thus are the about sought type for serenity running in one case set up properly.

Concluding edited: Dec 24, 2021

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