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Old 07-23-2008, 11:46 PM   #1
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Default Stripped Bevel gear in MBX5R, why?

Hey all

On the weekend i had to pull out of the final for what i thought was a bad bearing which eneded up being a stripped bevel gear in the rear diff.

I have since pulled the front apart aswell to find it had started wearing also.

This buggy is not very old at all so it has to be how i had them setup... I have rebuilt the diffs fairly often and never noticed too much metal inside the diff case and on the chassis but this time there were metal flakes in the front and in the back...

I had it setup with no shims, used grease (Mugen) on the bevel to conical gears... When i put them together last time i thought there wasn't much slop in the diff case to allow for shims but now i have had problems and looked further i can see i can slide the diff approx 2mm sideways towards the gear and away...

Can I assume have the mesh to loose has caused the stripping?

I can fit 2 shims in to tighten it up and it becomes fairly tight and nosiy or i can fit 1 shim in and have around 0.75-1mm play. what kind of mesh am i looking for?

The front bevel has not stripped but has not much life left. all the teeth are sharp.

Would using too much grease cause this? i ask because i have service these diffs fairly often and other then my first run this is the only time there has been metal shavings and problems?

i mention my first run as i found a fair amount of shavings on the chassis and i just put this down to running in the gears... as the bevel gear and conical gear looked fine.

thankyou all!

sorry its a bit long didn't want to miss anything important..
MBX5R - OS VSpec - Futaba 3PKs - Hitec 5955's- LRP Lipo - Proline
MBX5T - RB C6 L2G - Futaba 3PKs - Hitec 7955's - LRP Lipo - Proline
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Old 07-24-2008, 12:02 AM   #2
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You have to use those shims on the outside of the bearing races to get rid of that side to side play. Whether you use one or two diff gaskets will affect how you shim the diff. But I shim mine so they feel smooth but as tight as I can get them. I'll usually spin them and feel one slight tight spot in teh 360* rotation. I run the car and re-check. 99.9% of the time the tight spot goes away.
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Old 07-24-2008, 01:36 AM   #3
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Tony is spot on.

I've also seen alot of brake makes them wear alot more quickly. I've noticed that braking is much harder on the drive train that accelerating. I used to run a crap load of brake, but have since backed it off to just enough.
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Old 07-24-2008, 06:19 AM   #4
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What Tony said is spot on, the only thing I can think of to add to that is cheek your diff case and be sure you are using the correct bolts. One the of guys I race with a few years back somehow put to long of bolts in the diff case, this distorted the case just enough that it would eat diffs.
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