Results 1 to 8 of 8
  1. #1
    RC Racer
    Join Date
    Apr 2017
    Posts
    109

    Diff Shimming Issues

    Hello all,

    Recently I have been struggling with the diffs in my mini summit. I recently replaced the rear bulkhead because the old one had a crack in it. However, this new bulkhead doesn't seem to accept shims. I put a single shim on the ring gear, and when i put the car back together to test it, there was binding coming from the rear diff. I also loosened up all the screws that are attatched to the bulkhead. Still the same result. Is this a common issue, or am I just the unlucky one? I know that this diff will strip if I don't shim it, but it binds when I do.

    I'm really just unsure of what is going on, and I would appreciate some help!

    Thank you!

  2. #2
    RC Racer
    Join Date
    Oct 2018
    Posts
    246
    What size shims you using? Seems like either the shim is too thick, or maybe, just maybe, you got lucky and it sits just right where you don't need a shim. Is there any movement from gear to gear with no shim installed? I've never had a mini summit, so just going off general diff shimming experience.

    Sent from my SM-G970U using Tapatalk

  3. #3
    RC Racer
    Join Date
    Apr 2017
    Posts
    109
    Quote Originally Posted by Steve g View Post
    What size shims you using? Seems like either the shim is too thick, or maybe, just maybe, you got lucky and it sits just right where you don't need a shim. Is there any movement from gear to gear with no shim installed? I've never had a mini summit, so just going off general diff shimming experience.

    Sent from my SM-G970U using Tapatalk

    I am using the team associated 21141 shim set. I read around on the forums and everybody says to use these. The dimensions are .324x.409x.005. There's little to no slop between the ring and pinion gear either. The old bulkhead I was using was 10 years old when it finally cracked, so I'm assuming that it stretched and flexed a bit making the gears eventually strip. Hopefully this new bulkhead will solve the issue, but I just wanted to make sure.

  4. #4
    RC Champion grizzly03's Avatar
    Join Date
    Dec 2014
    Location
    Adirondacks
    Posts
    2,124
    I'll agree. If you are using thick shims you might not be able to install one. Shims come in different thicknesses. Depending on what shims you are using and the actual amount of gear play, dictates how many if any can be used.

    Shimming a differential doesn't mean you need to add shims. It is the process of trying to eliminate the excess play between the gears.

    EDIT: Those shims are thinner and if one makes it bind, it shimmed good already. I've noticed a difference between the old bulkheads and the new bulkheads with the cross-screw. The new ones hold up much better. That screw holds the bulkheads together. If your old ones didn't have it make sure to install one.
    Last edited by grizzly03; 07-18-2020 at 10:11 AM. Reason: posted at same time edit

  5. #5
    RC Turnbuckle Jr. Squeegie's Avatar
    Join Date
    Jun 2014
    Location
    San Gabriel, California
    Posts
    8,388
    ^What they said.

    When I did mine, I only needed one shim in the front. None in the rear.

    The older bulkheads didnít have the screw that goes in the side. This newer design makes for a better bulkhead with less slop.

    Use shims only as needed. Test test test...

    Have fun!
    Creativity is intelligence having fun. -Einstein

  6. #6
    RC poster
    Join Date
    Aug 2020
    Posts
    5
    If you are running the 4600kv set up you need to ditch the stock bulkheads and get the hot racing aluminium ones. Front and rear. They will still need to be shimmed though. You will also want a center diff if you don't already have one. The bulkheads, even shimmed, will last you maybe 3 packs before they wear enough to to strip the gears. I run 500k fluid in the center and 100k front and rear. I've ran probably 40 3s packs with the stock vxl, and another 10 with a castle 4600kv motor on 3s with zero issues so far.

  7. #7
    RC Champion zedorda's Avatar
    Join Date
    Sep 2015
    Location
    S.E. Michigan
    Posts
    1,412
    Shims are not always needed on new parts. Also using overly thick diff fluid will cause premature wear. 500K by 100K while trying to go over 40mph equals wrong application in most cases. Unless you only plan to go straight all the time.
    Last edited by zedorda; 08-22-2020 at 10:30 PM.

  8. #8
    RC poster
    Join Date
    Dec 2017
    Posts
    15
    I remembered when the original revo mini had so many issues with rear needing shim because it would start clicking

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •