Replacing Pinion Bearings

Replacing Pinion Bearings

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  1. #1
    JK Newbie
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    Default Replacing Pinion Bearings

    My 2011 JKU Rubi has developed a small rear diff whine which starts at about 35 mph. It happens when just coasting or just a small amount of accelerator load. From what I've read on various websites it's the pinion bearing preload being a bit too loose causing the noise. I don't know how this happened because I had a complete diff rebuild 18 months 20,000 miles ago because of broken pinion teeth. Since then I have done a lot of hard core 4wding and along the way twisted the L/H rear axle, which is now fixed.
    I thought I would see if it was the pinion causing the whine and maybe the pinion preload had changed because the crush sleeve loosened/pinched so I decided to give the pinion nut a very small tighten. Yep this worked a small amount by reducing the noise a little but I've notice the pinion seal has now started to leak a very small amount too.
    I don't won't to tighten the pinion nut anymore because I thought the seal may leak even more so the next step is to just replace the Pinion bearings, crush sleeve and seal & nut.
    Now here's the main question, I'm replacing Timken bearing with Timkens (same,same) Do I need to check and change the shims or will the ones there be the correct thickness? Same, same, so nothing should of changed right?
    Last edited by multihull; 06-16-2017 at 12:01 AM.

  2. #2
    JK Newbie
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    Default

    There is a lot of information on gear replacement. I read and did my own gears but definitely no long experienced expert. Having done mine and said that; pinion preload is done with carrier out. Assuming the backlash, and carrier bearing preload was good after rebuild, the carrier shims would be the same but must go back in each specific side. Seems the preload may have not been optimum or maybe a bearing race was not fully seated. For me; if I didn't feel comfortable with doing a gear swap, and or did not have the tools (dial indicator with magnetic base, inch pound non-click torque wrench in proper range) and additional setup shims, I'd take it to someone to replace pinion bearings. You're really going to do the complete setup process.
    Last edited by BRinSCupstate; 06-16-2017 at 06:19 AM.

  3. #3
    JK Newbie
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    So a shout out to other tech owners and mechanics for confirmation.

    If I use the same pinion gear and replace the 2 x pinion bearings with the same Timken brand I won't need to reset or change the existing pinion shim?

  4. #4
    JK Jedi Master ronjenx's Avatar
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    Default

    Quote Originally Posted by multihull View Post
    So a shout out to other tech owners and mechanics for confirmation.

    If I use the same pinion gear and replace the 2 x pinion bearings with the same Timken brand I won't need to reset or change the existing pinion shim?
    You'll be checking pattern anyway, so put it in with the same shims and see what you get. It's just like starting from scratch.
    The only difference is you're hopeful the original shims will be what it needs, whereas, with all new parts, you expect it won't be right the first time.
    08 Rubicon Unlimited
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  5. #5
    JK Newbie
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    Quote Originally Posted by ronjenx View Post
    You'll be checking pattern anyway, so put it in with the same shims and see what you get. It's just like starting from scratch.
    The only difference is you're hopeful the original shims will be what it needs, whereas, with all new parts, you expect it won't be right the first time.
    Yes I will do a recheck but I hope the lapping is good as I have no shims to swap over with. Jeep parts here in Australia are 3 to 4 times the price compared to the USA and they aren't as easy to find suppliers who stock them.

  6. #6
    JK Newbie
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    I would expect the pinion shim to be the same with new bearings. The procedure I used and read, for gear swaps, was to use setup bearings that were milled to slide on and off pinion shaft for setup purposes. From my gear change and reading, the new bearings should not make much difference but you're supposed to double check after final assembly. From setup bearings (old) to new, the shim was fine on mine. Hope it all works for you!

  7. #7
    JK Newbie
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    When i regeared i used old pinion bearings as set up bearings. Check on final set up with fresh bearings showed it had shifted pinion placement and i had to pull bearings and re set up...maybe it was a tolerance issue between the two bearing sets...but my point is have extra crush sleeves, pinion nuts, seals etc in case it needs another adjustment...or three. It is worth redoing because those gears really do need to be perfect. Aint no goodnuff with gearing.

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