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Blew front Diff bearings

Discussion in 'HPI Savage XL' started by Bboy86, Jun 5, 2018.

  1. Bboy86

    Bboy86 Member

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    after going through my XL after nearly2 hours of running, I found a blown bearing on the front Diff on the case side. I wonder when it happened...
     

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  2. olds97_lss

    olds97_lss Well-Known Member

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    That's something you have to keep a close eye on. Odds are, your rear one may be getting sloppy as well. What stinks about these kinds of diffs is that you have to take the internals out to swap bearings. Make sure to check for shims as there are probably some on there behind the bearings that tend to stick to the old bearings when you take them off.

    The savage uses 2 different sized bearings. 8x16 on the ring gear side and 10x16 on the cup side. The cup one tends to grenade more frequently, but when one blows or gets sloppy, I usually replace both. Would have been nice that since they are going with a larger ID if they also used a larger OD, like a 10x18. Then it would possibly hold up longer.
     
  3. Bboy86

    Bboy86 Member

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    This is the first time it has happened. The 10x16 bearings don’t look the most durable either. I will replace both bearings and check for shims that have stuck. Thanks!
     
  4. olds97_lss

    olds97_lss Well-Known Member

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    I've had savage trucks for quite a while, so I try to keep a close eye on the diff bearings. Especially now with them being harder to find without paying a ton. Funny how a $1 bearing can be so important!

    I just wish the diffs were designed with cups that came off via a set screw like traxxas trucks. Then it would be 5-10 minutes and much less mess to swap out new bearings. Granted, that's one more thing to make sure stays tight, but I'd prefer that over having to disassemble diffs entirely to change a bearing or to re-shim.

    Check the pinion bearings too. Also 8x16mm like the one diff bearing. They tend to hold up pretty well though, but once you've gone so far as to take the diff out, tear it apart and put new bearings on it, would be silly to not at least check them for any forward/side to side slop as well.
     
  5. Bboy86

    Bboy86 Member

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    I check the bearings after every run, but this is the first blown bearing. It is a pain to have to disassemble the diffs, maybe when/if the release an updated XL they may go in that direction.
     
  6. olds97_lss

    olds97_lss Well-Known Member

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    Almost all 1/8th diffs are built this way. The cups are part of the shaft. I don't know why... perhaps they can take more abuse... I have yet to run across an 1/8th diff that did not have the cups as part of the shaft. Found a few 1/10th that weren't traxxas.

    I don't know why it's this way, seems a bit nonsensical since those with 1/8th scale would be more likely to want to shim things more precisely to hand 1/8th scale torque. Having removable cups would make that even easier. Obviously, would also help with maintenance. If I had the means, I'd make my own, and see if it mattered. But I lack the skill or machining tools to do so.
     

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