Calling Any Rear End Gear Install Experts

Discussion in '2005+ Mustang GT 4.6L Tech' started by 1950StangJump$, Apr 6, 2020.

  1. 1950StangJump$

    1950StangJump$ forum member

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    I seem to have the worst luck getting gears in and reasonably quiet. 2008 4.6. Going from 4.10s to 3.55 to ready for more power.

    So, yesterday, I had the 3.55s installed by a VERY reputable mechanic who has done them a thousand times. I was with him to assist and learn, and he is very credible. Used the FRPP kit with carbon fiber clutch packs. Note, I already have a T56 Magnum XL with one piece driveshaft.

    Everything went in fine. At first attempt with shims, he got backlash to .010. However, the gear pattern wasn't to his liking. So, we removed everything, reshimmed the pinion, and got a good pattern. Rechecked backlash and reshimmed it and got to .008. Since spec is .008 to .012, we called that good. Buttoned everything up, bolts torqued to specs, and we're on our way.

    Pulled out . . . and the damn thing whines LIKE CRAZY on decel. It calms a little above 65MPH, but it is downright obscene from 50 to 35. Doesn't go away completely until you're at 25 MPH. The slightest tip of the throttle makes them quiet as a church mouse.

    We expected some noise because I have poly rear suspension parts. But, the mechanic said he has never had one sound that bad. So, we're going to try to reset it next weekend. He is ordering a new pinion bearing and crush sleeve, just in case the bearing was damaged when he pulled it back off to reshim the pinion. Also going to make sure the carrier didn't shift forward when load was put on it from not being shimmed tight enough.

    By the time we work on it, the gears will have about 100 miles on them, and my mechanic thinks they won't be ruined that fast if we get them set right.

    Any other thoughts?
     
  2. drive_55_not

    drive_55_not forum member

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    The gears will be fine,, I've installed used 4.88's and Motive 3.90's that everybody sez whines and gotten them quiet. The guy I got the 3.90's from sed they whined alittle. It's all in the setup.

    One thing I learned is to put tension on the carrier when turning it to check the pattern, I wrap a little cargo strap around it a few times and pull it as tight as it'll go.

    Spin the carrier BOTH directions so you can see what the drive and coast side look like..

    Here's what my current 3.08's look like, Unfortunately this is the best pic I have but you can see I start the pattern down on the toe and it has a fairly full swipe across the tooth.

    This is quiet on both drive and coast .

    Another thing I've learned and had a couple old gear guys say is don't get too hung up on the pattern, You can see that from that Yukon chart, As long as the pinion is deep enough on the tooth and you get a nice solid swipe across it and it doesn't whine.. Run it and don't worry about it ....

    I know it's a PiTA but it can be done ... Good luck ...

    FRPP-3.08_Pattern.jpg 8-8_Ford_Setup.GIF
     
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  3. 1950StangJump$

    1950StangJump$ forum member

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    Are you pulling on the carrier towards the rear of the car, and only while checking the pattern? Or also while checking backlash?
     
  4. Juice

    Juice forum member

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    Without pics of the contact pattern, I cannot advise.
    And as stated above, need to see both power AND coast side of the pattern.

    Grab a hold of the pinion at the rear Ujoint and see if you can move the pinion side-to-side. If there is play in the pinion bearings, that would cause a whine on decel only.
     
  5. 1950StangJump$

    1950StangJump$ forum member

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    Kind of an interesting piece of data, we test drove the car and had the bad decel whine.

    Put it back on the lift. We were tired and weren't taking it apart again right then. But, he noted the pinion had gotten loose somehow after being completely tight before.

    we pulled the driveshaft off and torqued it down snug again. No effect - still whined on decel only and the same. We didn't put it back up again to see if it was getting loose again.
     
  6. Juice

    Juice forum member

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    I had one pinion come lose on one of my installs after a few days of driving. Found pinion lose and getting progressively loser and louder on decel. That is why I asked.

    I did not swap the pinion bearing race in the housing. (Never had an issue, as long as the race was in good shape.) The root cause turned out to be a bearing to race mismatch that ate the larger pinion bearing up. New race AND bearing, and it has been fine since than, two years later.

    I ran into this just once, in all the diffs I built/rebuilt.

    And if your pinion is moving/has moved, the contact pattern and backlash is no longer where it was set up.
     
    Last edited: Apr 6, 2020
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  7. Juice

    Juice forum member

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    Double post
     
  8. rocky61201

    rocky61201 forum member

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    FWIW I replacing my gears right now and because we have so much time on our hands due to COVID-19 I removed the entire axle from the car, lol. Now I can measure and set up nice and comfortable instead of laying on my back. That way I don't make a hasty and bad decision because I'm fatigued from crawling in an out from underneath the car.
     
  9. Juice

    Juice forum member

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    lol Great access for sure!
    I would only go that far to pull the housing, it would be to paint or powder coat housing.
     
  10. Rick Simons

    Rick Simons Member

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    Great minds think alike rocky61201! I pulled my entire axle and put it on the bench to redo it after I had the same kind of noise with what looked like a good pattern, etc. I reinstalled the factory pinion shim, reset the backlash/preload/pattern, and all is well. Turns out I had the pinion too close to the axle centerline, even though everything seemed to look right. And don't worry about the miles you've already put on them; Ford laps them at the factory then puts the black oxide coating on, so unless there's something drastically wrong, the coating coming off is about the only wear you'll see. Mine had about 120 miles on them when I took it back apart.
    One other thing I did was use a solid pinion shim setup as I've never liked the crush sleeves, which BTW are a one-time use item. I also bought an extra rear pinion bearing and honed out the ID so that it would just slip over the pinion. This allowed me to assemble/disassemble the pinion as many tines as necessary without having to press the bearing on and off.
     
  11. rocky61201

    rocky61201 forum member

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    I've got mine completely torn down and haven't started assembly yet. Waiting on a new drift punch to get my bearing races out. But when I get started if I'm not happy I will probably order the solid spacer shim setup too. I hate the crush sleeve too but since I'm not on my back this time crushing the sleeve slow and proper shouldn't be as hard as before. We'll see. I can also see myself honing out a spare pinion bearing as well if things don't go as planned.

    The noise I had currently have I suspect was using a gearset other than FRPP. Because the install I did was within spec and things looked ok. But this go around got a fresh FRPP 3.55 and rebuild kit and took the axle out just to be sure. Like I said I got the time so might as well do the best I can possibly do. Plus now I get the chance to clean everything up and re-lube all my suspension components.
     
  12. Norm Peterson

    Norm Peterson corner barstool sitter

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    A length of mild steel or possibly aluminum round stock might be better than a hardened steel punch. Cheaper, too.


    Norm
     
  13. 1950StangJump$

    1950StangJump$ forum member

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    So . . .

    After spending 6 hours last Sunday on going from the 4.10s to the 3.55s, only to have the obscene decel whine, my mechanic I and set out again to fix it yesterday afternoon. After much thought, we agreed with the sentiment here that something was up with the pinion depth or pinion bearing. So, he bought a new Timko bearing and race, and we installed it. Set pinion depth and got backlash to .010. Wear pattern looked good.

    And it whined like a MOFO still. He was beside himself, as he has done hundreds of these. He had never had one give him such a hard time.

    So . . .

    We were left with the theory that the FRPP gears I bought were bad. On a whim, we decided to reinstall the original 3.55s that came in the car in 2008 (I had brought them with me, just in case). They had about 21k miles on them. It was a PITA, cause we didn't know where to start on pinion depth because the shims were gone, so there was lots of trial and error. In the end, he got the backlash to .010 again, but the pattern wasn't "perfect" in his mind. It was 9PM by this point, and we decided to get it back together and expect them to sound like crap. I was all prepared to order new gears, and we would try again next weekend.

    And the darn things are quiet. And, I mean as quiet as I could ever expect. If I really struggle, I can hear the slightest decel noise from 45 to 25 . . . but it's so low, it could be the transmission or the tires. And, besides, I have a full BMR poly rear suspension -- so I expected some noise. Yet, somehow, these 12 year old gears are as quiet as I could ever expect.

    Go figure. Anyone want to buy some almost new FRPP 3.55s? They have a great supercharger whine to them! LOL
     
  14. GlassTop09

    GlassTop09 Member

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    I feel for ya...…….glad you finally got her sorted out though!
     
  15. rocky61201

    rocky61201 forum member

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    Quick questions for you guys. The new inner pinion bearing race (the bigger one) is being a stubborn mo-fo to pound into the axle flush. Would you or have you put the race in the freezer over night to get it to shrink just a little bit and not worry about it cracking if you still have to hammer on it a little bit?

    A simple yes or hell no!!! will suffice.

    I've got the bearing race driver kit and my 5 lb hammer and also I got some threaded rod and nuts to attempt pressing both inner and outer races at the same time like the manual says to do. Both methods are being a stubborn mo-fo.
     
  16. Juice

    Juice forum member

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    I never froze it. Its not that tight. I tap it in with a brass drift. Just have to tap at different spots to walk it in evenly.
     
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  17. 1950StangJump$

    1950StangJump$ forum member

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    We didn't need to do that either
     
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  18. Norm Peterson

    Norm Peterson corner barstool sitter

    Age:
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    I found it easier to start the large outer race using some allthread and a couple of short steel bars. Final seating all the way to bottoming used the allthread through the race driver adapter. Checked all around with the thinnest feeler gauge (0.002") and all was good.

    Make sure you lubricate the threads with some sort of grease, as you want as much of the torque you apply with the wrench to go into pulling the race home. Not beating up the threads.

    Installing large race 1.JPG

    Installing large race 2.JPG

    IMG_3281.JPG


    Norm
     
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  19. rocky61201

    rocky61201 forum member

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    Thanks guys. Thanks Norm. I'll try that method.

    Edit - Thanks again. I got the races in. A little more light (might be time to get glasses) and a little more patience and little advice goes a long way.
     
    Last edited: Apr 13, 2020
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