rear diff question

Discussion in 'KJ General Discussion' started by MarksmanAkula, Nov 19, 2020.

  1. MarksmanAkula

    MarksmanAkula Akula

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    So this weekend I'm planning on taking apart the rear diff to install new pinion bearings.

    What I want to know is if I'm taking out the old gears and replacing only 2 bearings, and putting the same gears back in, do I need to set tolerances? or will the old gears and such still hold their shimmed tolerances?

    Basically, if I take it out can I put it back in with no trouble?
     
  2. tommudd

    tommudd Moderator Staff Member Moderator

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    Just the pinion bearing?
    If you are in that far I'd do all bearings and seals
     
  3. MarksmanAkula

    MarksmanAkula Akula

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    Well @tommudd I do have a few other bearings on hand, and all seals of course. But mostly yes pinion, still trying to hunt down a vibration. What I care about most is if I can remove everything then stuff back in, same gears, shims, etc.
    If I can fantastic.

    If I have to reset backlash tolerances and such, then ill have someone more reputable do the work
     
  4. JeepJeepster

    JeepJeepster Full Access Member

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    You'll have to reset backlash no matter what after removing the carrier. The 8.25 uses side adjusters so you cant just pop the carrier out and pop it right back in. You must follow the procedures in the FSM when setting the backlash.

    For the pinion, you can just reuse the shim behind the inner pinion bearing and all will be well.

    You'll need a good dial gauge to check the backlash. I would check it before removing everything and also check the gear mesh just to see what it looks like.

    Buy timken bearings and races, thats what the Jeep has now. I also bought a nice long brass punch to punch out the old races and also bought a good pinion holding tool from bleepin jeeps. Crushing that new crush sleeve IS NOT fun...... AT ALL.
     
  5. MarksmanAkula

    MarksmanAkula Akula

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    As I figured, I dont have the tools or time window to do all of that.

    If you'd be so kind, could you get me a complete list of tools that would help?
    Local shop quoted around $700 for a complete bearing/seal rebuild.
     
  6. Big Al

    Big Al Let's get Cracken

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    image.jpeg Also, just for speculation, I would remove the differential cover and check the side gears and spider gears.
    Then seal it up and add new oil, rebuild at a later date.
    Picked up my jeep this summer and it had a howl when accelerating and then stopped when I took my foot off the gas.
    Opened mine and found the spider and side gears with chunks out of them.
    Crown and pinion gear look good.
    You may need to order a set of these gear sets too.
     
  7. JeepJeepster

    JeepJeepster Full Access Member

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  8. MarksmanAkula

    MarksmanAkula Akula

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    I believe I've heard of it, but do you have a link to it? just for reference.

    And I've seen videos of people synching those things down to 210FT/LBS. Does not look like fun at all.
     
  9. JeepJeepster

    JeepJeepster Full Access Member

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    My bad, you'll either need to buy the whole rebuild kit or try to piece the bearings n such together. Nitro gears use koyo bearings, idk the other use. 210lb/ft didnt phase my pinion. The koyo outer bearings was very tight on the pinion where as the factory outer pinion bearing almost went on by hand, so I think this made it a little harder. My precision torque wrench goes up to 250lb/ft and there was still alot of play in the yolk. I wedged a breaker bar on the lower control arm and used my floor jack with another breaker bar to get it tight. I thought for sure one of my break bars was going to snap. I bet I had to reset 40 times, it was miserable. Youve got to go very slow and keep checking the rotating torque for the pinion. You'll need an inch lb torque wrench also. And a set of big sockets, I cant remember what size the pinion nut was but I think it was 32mm.

    https://www.nitro-gear.com/Chrysler8-25-Rear-Nitro-Master-Install-Kit-p/mkc8.25-b.htm

    https://www.quadratec.com/products/...yuOFC8LcXEHEyyHATzi5wtLfWDdsbIxhoCjSMQAvD_BwE

    https://www.amazon.com/Yukon-Gear-YK-C8-25-B-Differential/dp/B0078UB2P2

    https://www.amazon.com/GearWrench-2...que+wrench&qid=1605881333&s=automotive&sr=1-8

    Yukon says that kit only does up to 04, which I dont understand. Nitro says 2010.
     
  10. MarksmanAkula

    MarksmanAkula Akula

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    Thank you for the list of tools and different rebuild kits!

    I'm not hearing any bearing noise lately, I just have that weird intermittent vibration, that I'm believing more and more is the transmission going bad or starting to shimmy.

    But when the time comes to freshen up the rear diff that list helps immensely, thank you for your time!