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    1. #1
      Join Date
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      Anyone here an expert with gear setup in 9 in rear ends?

      I cant take any more whining, but enough about my kid, lets talk about my car......I've had this on-cruise whine at 50+ mph since I got this car on the road. under heavy load, and under coast its quiet. so I pulled my rear diff apart to see what's going on. Seems like maybe I'm running on the end of the ring teeth too much? I'm wondering if I should shim the pinion out a little further, and push the ring gear closer to the pinion. Somebody set me straight here.
      Attachment 191967Attachment 191966Attachment 191965Attachment 191968



      Cheers.
      Zach

      "It so repulsive to see such a beautiful 1970 Mustang, with the other teams engine transplanted into it. I know that car would spit that thing out if it could. Just ruined it, when everything else about the car is so nice." - Bossed


    2. #2
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      All the setup in the world will likely not fix it. You could try GearFX gears but I’ve seen complaints about them too.

      There’s a bunch of threads about this.

      Don
      1969 Camaro - LSA 6L90E AME sub/IRS
      1957 Buick Estate Wagon
      1959 El Camino - Ironworks frame
      1956 Cameo - full C5 suspension/drivetrain

    3. #3
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      Quote Originally Posted by dhutton View Post
      All the setup in the world will likely not fix it. You could try GearFX gears but I’ve seen complaints about them too.

      There’s a bunch of threads about this.

      Don

      are you saying that the gear set is just going to be noisy, and I haven't done the setup poorly enough to cause issue? Its Motive Gear BTW.
      Zach

      "It so repulsive to see such a beautiful 1970 Mustang, with the other teams engine transplanted into it. I know that car would spit that thing out if it could. Just ruined it, when everything else about the car is so nice." - Bossed

    4. #4
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      Quote Originally Posted by Zachalanche View Post
      are you saying that the gear set is just going to be noisy, and I haven't done the setup poorly enough to cause issue? Its Motive Gear BTW.
      Pretty much. This is a problem with just about all 9” gears. GearFX claims to have better quieter gears. Some guys are going to a Ford 8.8” rear with OEM gears to get a quiet set of gears. John Parsons has quite a lot of experience with this. Maybe he will chime in.

      Stielow gave up on 9” rear ends due to the whine.

      Don
      1969 Camaro - LSA 6L90E AME sub/IRS
      1957 Buick Estate Wagon
      1959 El Camino - Ironworks frame
      1956 Cameo - full C5 suspension/drivetrain

    5. #5
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      Quote Originally Posted by dhutton View Post
      Pretty much. This is a problem with just about all 9” gears. GearFX claims to have better quieter gears. Some guys are going to a Ford 8.8” rear with OEM gears to get a quiet set of gears. John Parsons has quite a lot of experience with this. Maybe he will chime in.

      Stielow gave up on 9” rear ends due to the whine.

      Don

      I do have an oem set of gears i could swap in.

      I wish someone would build a 3rd member that used the 8.8 stuff but bolted into a 9in housing. the 9 in design is so parasitic.
      Zach

      "It so repulsive to see such a beautiful 1970 Mustang, with the other teams engine transplanted into it. I know that car would spit that thing out if it could. Just ruined it, when everything else about the car is so nice." - Bossed

    6. #6
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      Don’t take my word alone for all this. Send John Parsons a PM. Icemanrd also has a lot of experience with noisy gears.

      Don
      1969 Camaro - LSA 6L90E AME sub/IRS
      1957 Buick Estate Wagon
      1959 El Camino - Ironworks frame
      1956 Cameo - full C5 suspension/drivetrain

    7. #7
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      Aug 2019
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      Nashville, TN
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      Country Flag: United States
      Just my personal experience with a newly built Ford 9” with 3.50 gears, Eaton TrueTrac, and set up by Quick Performance. It’s perfectly quiet under load, cruise, coast, and no leaks.

      I beat it up pretty good at autocross events and drive all the way to and from. All I did was join the center section to the housing, install the axles, and followed their break-in procedure. I highly recommend Quick Performance; great customer service.

    8. #8
      Join Date
      Aug 2004
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      I have also had the noisy gear experience with a QP unit, switching to a GearFX unit. Bought one with REM polishing and Dyno’d. Hoping to drive the car in the next month. Hey Don, where did you see problems with the GearFX stuff?
      Chris
      1968 Chevy Camaro SS
      LS3/T56 DSE suspension


    9. #9
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      Anyone have experience with John's Industries?
      69 Camaro convertible, 410, M22, 8-pt cage therapy program. SOLD.
      68 camaro - SOLD
      67 Bel Air - New street project with perfect floors, frame and trunk!

    10. #10
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      Quote Originally Posted by 130fe View Post
      I have also had the noisy gear experience with a QP unit, switching to a GearFX unit. Bought one with REM polishing and Dyno’d. Hoping to drive the car in the next month. Hey Don, where did you see problems with the GearFX stuff?
      I think I read it over on the other forum but I’m not positive.

      Don
      1969 Camaro - LSA 6L90E AME sub/IRS
      1957 Buick Estate Wagon
      1959 El Camino - Ironworks frame
      1956 Cameo - full C5 suspension/drivetrain

    11. #11
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      I dug out an old R&P that i had (same ratio of 3.70:1), and there are some significant differences in the ring gear. the ford gear is a little smaller than 9" and the motive gear is a little bigger than 9". the Pinions appear to be the same dimensionally, but the ring gear has longer teeth. I'm not sure if this is at all related to the issues i am having, but I found it interesting. What's even more interesting, is the old ford gear set doesn't seem to show as much wear, the mileage is unknown on the old ford set, but i would assume its more than the 150 miles I have on the Motive gear set. it almost seems like there is some sliding going on between teeth rather than rolling. The oils came out looking like the paint on a bass boat...ok maybe not that bad, but i wonder if this is excessive for break in.

      Also thanks to everyone for your input. and advice on different shops, but I really want to solve this one for the sake of my own knowledge, and I'm cheap. Sooo, If anyone is good at reading gear patterns I'm all ears. I thing i might be able to find some pics with the yellow grease from when i set up the rear end initially too.

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      Zach

      "It so repulsive to see such a beautiful 1970 Mustang, with the other teams engine transplanted into it. I know that car would spit that thing out if it could. Just ruined it, when everything else about the car is so nice." - Bossed

    12. #12
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      Here are the pictures i took during the initial build. looks like i might have been on the upper end on backlash. I think.010-.012 is spec, and i have heard, some go with .008 on high performance applications due to growth at high temperatures.

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      Zach

      "It so repulsive to see such a beautiful 1970 Mustang, with the other teams engine transplanted into it. I know that car would spit that thing out if it could. Just ruined it, when everything else about the car is so nice." - Bossed

    13. #13
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      Aug 2007
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      434
      I used John's on my 67 Nova and it was very quiet.

    14. #14
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      Update, As found backlash measured at .018-.019. so that seems like a red flag. No signs of the adjuster nuts moving, or the caps being loose. based on my old picture it looks like i was around .012-.013 when i built this diff. So, over the course of 150 miles the backlash has increased .005-.007. maybe I didn't have enough load on the adjuster nuts and the backlash increased as everything settled into place, or there has been enough wear to create the increased backlash.

      Question is, can i just reset the lash, recheck the mesh pattern, and be on my way? or will these gears forever whine.

      I have read a lot of different things, but it sounds like factory gears should be .010-.016, and aftermarket should be .007-.010. since these are aftermarket, i currently have double the prescribed backlash.


      Funny thing is that in my younger / dumber days I have set backlash just by feel, no noise no issue. Probably just luck. or maybe there was enough rubber in the suspension to keep me from hearing the noise.
      Zach

      "It so repulsive to see such a beautiful 1970 Mustang, with the other teams engine transplanted into it. I know that car would spit that thing out if it could. Just ruined it, when everything else about the car is so nice." - Bossed

    15. #15
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      I tried reducing backlash to and the pattern went way toe, on the drive side. so I moved the pinion back (adding shims on a 9"), and readjusted backlash to .08, and I'm now having a hard time getting any kind of a pattern in the yellow grease. and the Coast side is on the toe of the tooth.
      Zach

      "It so repulsive to see such a beautiful 1970 Mustang, with the other teams engine transplanted into it. I know that car would spit that thing out if it could. Just ruined it, when everything else about the car is so nice." - Bossed

    16. #16
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      This is the best pattern I can get. the gear seems to be worn in a way where the pattern doesn't show up on the center of the tooth, rather an outline shows up. I know this is common if you just spin the gears, but I am applying as much counter force as I can to press the teeth together. right now I have a .006 shim on the pinion, and .009 backlash. The coast side (concave) of the teeth might be a little toe heavy, but the drive side (convex) is confusing, there's a contact line where the tip of the pinion gear tooth lands, and contact on the end of the ring tooth. both extend across most of the tooth and wear is heavier toward the toe. It seems like i am close to where things need to be, but the pattern is weird due to existing wear. I could relax the backlash a little and still be much tighter than before. I'm trying to decide if I think I can wear this gear back into shape and have it be quiet....at least quiet enough for a loud car. or do I start trying to set up the old gears.
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      Zach

      "It so repulsive to see such a beautiful 1970 Mustang, with the other teams engine transplanted into it. I know that car would spit that thing out if it could. Just ruined it, when everything else about the car is so nice." - Bossed

    17. #17
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      I know others have had occasional luck with 9" setups that run "quiet", but I never have. I've spoken and corresponded with many others over the years, including some of the manufacturers, and I've concluded that it's just not part of the engineering criteria for the aftermarket. Factory gears are "triple-lapped" whereas most aftermarket sets are "single-lapped". I admit I've not used any of the new "double-lapped" sets coming on the market in the past couple of years, so they might be better.

      In any case, if you want OEM noise levels, I'd use a Ford 8.8 setup. It's nearly as strong, has less parasitic loss, and can be had with 3" axle tubes, 31 spline axles, and any differential you can name. The best bit is that Ford Motorsports still manufactures and sells R&P kits. You can even find new housings if you look for them.
      John Parsons

      UnRivaled Rides -- Modern upgrades for your ride.

      UnRivaled Rides recent project -- LS9-powered 69 Camaro

    18. #18
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      I had this on order with Summit:

      https://www.summitracing.com/parts/ugr-s007

      The order was cancelled and now it shows as unavailable. I don't know if US Gear decided not to make these, but supposedly they were going to use a different manufacturing process that made the gears quiet.

      My Cougar had a OEM 4.30 gear set in it and it was dead quiet.

      Andrew
      1970 GTO Version 2.0
      1967 Cougar build
      GM High-Tech Performance feature
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      Dr. EFI
      I deliver what EFI promises.
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      Please get in touch if I can be of service.

      "You were the gun, your voice was the trigger, your bravery was the barrel, your eyes were the bullets." ~ Her

    19. #19
      Join Date
      Aug 2004
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      Texas
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      Towards the end of this article a section titled "Gear Ratio Selection and Tooth Combinations" - don't know how valid it is but at least its a methodical way at looking at it:
      https://www.diyford.com/ford-axle-ri...ssembly-guide/
      -Bob (66 Nova)

    20. #20
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      Quote Originally Posted by BBPanel View Post
      Towards the end of this article a section titled "Gear Ratio Selection and Tooth Combinations" - don't know how valid it is but at least its a methodical way at looking at it:
      https://www.diyford.com/ford-axle-ri...ssembly-guide/

      thanks for the link, very informative. interesting that the aftermarket 3.70s are reported to be noisy despite it being a hunting ratio. Maybe I need to move to 3.89s if I end up having to buy another set.

      the info about gear break in was good too. Foolishly, the first thing I did was get the car dyno tuned, this was back when the car had no glass, doors, fenders, etc. so the current gear set didn't see any break in miles. I wonder if I have damaged gears that would have otherwise been quiet had they seen some easy driving first. there does seem to be a lot of wear (for 150 miles) , and a lot of metal in the oil. I don't know how much of that is expected during break in.
      Zach

      "It so repulsive to see such a beautiful 1970 Mustang, with the other teams engine transplanted into it. I know that car would spit that thing out if it could. Just ruined it, when everything else about the car is so nice." - Bossed

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