Axles' gears skipping: what to do?

[utieh]

I need some help with a problem I still can't figure out after months.
Thanks in advance for reading.

I started a build with SSD's Diamond axles.
From the very beginning the gears were skipping while hitting some obstacles:
- going forward, the front axle's gears skip
- going in reverse, the rear axle's gears skip

Separately each element runs smoothly (transmission, front axle, rear axle), drive shafts do not bind.

I ordered some shims to reduce the play and the problem persisted

I added more shims till there were only 0.5mm of play on the pinion's shaft
I also installed new HD gears (Axial) since I started to see some wear on the original one (also Axial HDs).

Still the same, and it gets worse with time (end of the 2nd battery pack)

I thought the SSD axles were the problem so I ordered a set of new stock Axial axle casings (first gen).

It's a little bit better but I feel it's going to get worse like before.

Any idea what the problem could be? Anyone had experienced the same thing?

Thanks,

Gilles

 

[FormallySkullking]

Make sure your drive shafts are fazed, sounds stupid but it makes a difference. With the one piece axles you definitely need the shim on the output pinion gear. I've found the original multi piece axles dont need the shim

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[utieh]

What do you mean by "fazed"?
Thanks for your help.

Make sure your drive shafts are fazed, sounds stupid but it makes a difference. With the one piece axles you definitely need the shim on the output pinion gear. I've found the original multi piece axles dont need the shim

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[FormallySkullking]

Make sure the screws are aligned up on both outputs

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[utieh]

I see.
At some point, 2 screws were too long and the diff cover could not be flush, I thought it was the reason for the skipping but after fixing the screw size, the grinding persisted.

Make sure the screws are aligned up on both outputs

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[utieh]

Could it be because I don't use a slipper in the transmission?

 

[FormallySkullking]

I'm not sure, it's hard to say

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[Natedog]

Nothing to with not running a slipper clutch.

Ime once r&p gears get skippy, they gotta be replaced. Always check gears if they need shimmed. Axle housing could have hairline crack, poor tolerance allowing bearings to wiggle around even though they’re shimmed. Housing material could be too thin and flexible, all things I’ve seen. Hard to know across the webs, but keep after it and let us know what you find.

 

[utieh]

The build started with SSD housings: do you think that they could had damaged 2 sets of R&P (almost since the first battery pack) and now those same R&Ps skip in the stock axle housings?

There's almost zero play which is something I've never had to do before in both axles, there should be more tolerance.

One last note, none of the axle gears look to have that much wear.

Nothing to with not running a slipper clutch.

Ime once r&p gears get skippy, they gotta be replaced. Always check gears if they need shimmed. Axle housing could have hairline crack, poor tolerance allowing bearings to wiggle around even though they’re shimmed. Housing material could be too thin and flexible, all things I’ve seen. Hard to know across the webs, but keep after it and let us know what you find.

 

[utieh]

Here's a close up photo of the first set of gears aftr 5 battery packs:

Is the wear normal?

 

[RABIDFOX]

That pinion gear needs to be shimmed.

As to phasing the drive shafts, it must be done in order to eliminate any wobble and/or what I call bunny hopping. The concept is the same for your 1:1 off road rig as your scale RC rig. Shimming the pinion will reduce premature wear, backlash and grenadine the diffs.

 

[lonleycreeper]

It does not look normal to me.

GEAR TOOTH CONTACT PATTERNS :: 1993 :: Jeep Cherokee (XJ) :: Jeep Cherokee :: Online Manual Jeep

https://khkgears.net/new/gear_knowledge/gear_technical_reference/gear_backlash.html

 

[utieh]

I started building those axles without enough shims so I guess they went bad at the very beginning. Now there's almost no play which is not great as well.
I guess I'm going to get a new set of HD gears, hope it will work this time with the stock axles.

From the wear pattern, it indeed shows the gears need shimming, I never imagined they'd get bad as fast:

 

[Natedog]

...do you think that they could had damaged 2 sets of R&P (almost since the first battery pack) and now those same R&Ps skip in the stock axle housings?

Yes.

That pinion gear needs to be shimmed.

As to phasing the drive shafts, it must be done in order to eliminate any wobble and/or what I call bunny hopping. The concept is the same for your 1:1 off road rig as your scale RC rig. Shimming the pinion will reduce premature wear, backlash and grenadine the diffs.

Yes.

It does not look normal to me.

GEAR TOOTH CONTACT PATTERNS :: 1993 :: Jeep Cherokee (XJ) :: Jeep Cherokee :: Online Manual Jeep

https://khkgears.net/new/gear_knowledge/gear_technical_reference/gear_backlash.html

Agreed.

 

[utieh]

I'm rebuilding both axles today with new HD gears.

I added one more shim on the rear axle: it turns both ways when I spin the pinion's shaft, but when turning the wheel, it only goes backward and it is locked when trying to spin the wheel in the opposite direction.
There's a minimal amount of play and there's no binding.

 

[HumboldtEF]

when turning the wheel, it only goes backward and it is locked when trying to spin the wheel in the opposite direction.

Is this with the driveshafts attached or not?

The driveshaft needs to be attached to do a good test as it keeps the pinion in place, without it the pinion will ride up the ring gear and feel crunchy.

 

[utieh]

It is attached now but it's still lock one way.
There almost zero play when attached but it drives very smoothly in the opposite direction.

I could try it like that as it doesn't bind/lock if turned from the driveshaft.

Is this with the driveshafts attached or not?

The driveshaft needs to be attached to do a good test as it keeps the pinion in place, without it the pinion will ride up the ring gear and feel crunchy.

 

[HumboldtEF]

Did you just add a new set of wheels? I'm just wondering if you might have some interference at the wheel. You could try loosening the wheel nuts and seeing if it spins any easier.

or is it possible its shimmed too tight maybe? how does it feel with the shim you just added removed?

 

[utieh]

It doesn't turn without a wheel too.
I checked if the gear was laying flat on the spool and it does.
What I don't get is that Axial doesn't recommend shimming on its instruction manual, so could it be the opposite now and there's not enough tolerance?

Did you just add a new set of wheels? I'm just wondering if you might have some interference at the wheel. You could try loosening the wheel nuts and seeing if it spins any easier.

or is it possible its shimmed too tight maybe? how does it feel with the shim you just added removed?

 

[HumboldtEF]

Are you shimming the same amount as you did with the last housing? I ask because each housing is likely to be different.

I'd try loosening it up a bit to see how that feels.

Also where are you shimming? the ring gear, pinion or both?

I dont have any experience with the original SCX10 axles but I've done 3 of the 10.2 axle sets. I dont think I've ever had to shim the pinion its always been the ring gear which means very little since its a different design, just an example I suppose.