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A solution found to the Hot Racing motor mount/center diff fitment problem...

Discussion in 'Kraton' started by Bigfella, May 18, 2017.

  1. Bigfella

    Bigfella Well-Known Member

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    Like many I bought the Hot Racing motor mount and center differential holder. They are well made parts and the motor mount offers unheard of convenience when servicing your truck.

    The major problem is that when used together, they create front and rearward play in the center differential that equals .4mm. This is unacceptable. Having the spur gear move backwards and forwards on the pinion .4mm while under power is a recipe for bad things to happen.

    What to do?

    I contacted Hot Racing about this issue. They said they were unaware of this issue but would look into it. That's great but how does that help those of us who bought the parts but can't use them?

    I experimented with many fixes and finally found one that works. It allows you to use both the HR motor mount and the HR center differential holder without any play. The fix is rock solid.

    You have to buy these shims:

    https://www.amainhobbies.com/protek-rc-8x12x0.1mm-pinion-gear-washer-10-ptk-h-5909/p188797

    Take 4 shims (which equal .4mm) and place them between the center differential spur gear and the ball bearing. This is on the external, rearward side of the center differential. It is essentially externally shimming the center diff. It takes all the play out.

    Their you go. Go ahead and enjoy the convenience of the motor mount and the strength of the center diff holder......without the dealbreaking front rear play. :)
     
    Hypnotoad, 10pas2, rcdabbler and 4 others like this.
  2. WoodiE

    WoodiE Kind of good admin
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  3. Exceeded

    Exceeded Well-Known Member

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    Thank you Bigfella! It seems that the veterans here are really looking out for the new guys! What you mentioned about the shims being placed on the rear ward side of the centre differential,do you mean the front diff's dog bone's rear where the dog bones end ball bearing where the part of the plastic mount for the centre differential is?
    Sorry. Had to clarify as different vehicle has different setups. (Like the vorza has a different setup from the serpent cobra 811 be) thanks in advance!
    Cheers
     
  4. Bigfella

    Bigfella Well-Known Member

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    I'll post a pic for you.
     
  5. smithgpz

    smithgpz Well-Known Member

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    thanks for the info.i have the diff support and was looking at the motor mount. does the motor mount stay secure when tight?
     
  6. Bigfella

    Bigfella Well-Known Member

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    Yes. My HR motor mounts in both my Kraton and typhon have been rock solid and stay secure.. No problems so far. I use blue loctite on the motor mount plate screw. If I ever start having problems I'll use red loctite as it is easy to remove with a heat gun.
     
  7. rcdabbler

    rcdabbler Well-Known Member

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    That HR motor/center diff mount is one of the hop-ups I ordered to build up the pre-roller chassis I purchased. Thanks for the tip! I'm ordering a pack of those washers.
     
  8. Exceeded

    Exceeded Well-Known Member

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    Hello Bigfella. By shimming the rear wards diff bearing do you mean that it's here?
     

    Attached Files:

  9. Bigfella

    Bigfella Well-Known Member

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    Excuse the mud lol. The shims go here. You will have to take the diff apart to properly place the shims as they go in between the rear bearing and the spur gear. You can slide them right onto the protrusion on the spur gear. Then reassemble diff as normal.
     

    Attached Files:

    #9 Bigfella, Jun 12, 2017
    Last edited: Jun 13, 2017
    Exceeded likes this.
  10. Exceeded

    Exceeded Well-Known Member

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    oh my Bigfella! thank you so much! it is so clear right now! btw, no car is too clean after unboxing.
    thanks for the pic! it certainly helps a lot
    ;)
     
  11. Sully_

    Sully_ Well-Known Member

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    How is this fix holding up for you? Has anyone else tried ? i have both , and the shims are on the way. Hoping this fixes it :D
     
  12. Sully_

    Sully_ Well-Known Member

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    OK . This 100 percent fixed the issue. For some reason though i needed 6 shims to completely eliminate the slop. with 4 i still had some play.
     
    WoodiE likes this.
  13. msmy300z

    msmy300z Active Member

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    Anyone have trouble with fitment of the diff bearing with this mount? I have tried to place my diff 2-3 times and it always gets stuck before bottoming out. I have tried both sides of the diff to see if one bearing was off but it is the same either way. I also tried greasing the hole lightly and it still got stuck with ~1\3 to go. I mean stuck! I had to put the out drive on the floor and push down on the mount until it popped out.
    The same bearing goes into the stock mount easily. I don’t see any defects on the anodizing or anything... any help would be appreciated. I don’t know if it is a defect or if I will have this problem with any of them?
     
  14. olds97_lss

    olds97_lss Premium Member!
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    Couldn't you just use 13x16mm shims on the outside of the bearing like we do when shimming the front/rear diffs for better ring/pinion mesh? Less hassle than dry fitting it with the shims on the inside pushing the bearing out.
     
  15. joostin420

    joostin420 Well-Known Member

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