Diff cup mod

[BarHarborBasher]

Hi guys , wile I was assembling my center differential I decided to fix the issue with the binding of the sun/planetary gears in the differential cup.
It is fairly crucial that the sun gear is re-decked flat as possibly ... The removal is approximately .4 mm !!!!! .2 on each gear

I used a spare transmission output for the shaft with a locking collar installed to hold the sun gear tight against the output pin.

You'll also notice I end up cutting my transmission output and using the splined end for a custom output for my C/D.. I figured 4 surfaces of contact would be beneficial for the output as well as the sun gear.. The surface contact is WAY better than just a pin.. Plus I used Cobalt pins for engagement..

This mod leads to SMOOTH operating differential




Transmission output / collar



180/oil hone them 220/400 grit



This is for my custom center differential .. I used a transmission output for the sun gear engagement

[Deckard]

While rebuilding my rear axle last night I noticed the same thing with the sun gears. On this rebuild I'm using the HR diff cup, Bad Horsie Diff Locking Grease, Fast Eddie ceramics, and the old style ring and pinion. After getting it all together the diff felt a bit stiff and crunchy while rotating it outside of the housing. I'll be taking it all apart tonight and lapping those sun gears.

Thanks BHB.

[Lavaheadache]

A lot of times the washers under the sun gears are concave due to pressure from the pin over time and can be flipped over if you are experiencing a notchy diff. If it is too far gone just replace them. I'm willing to be that is where you are getting the tightness from.

[BarHarborBasher]

I assembled many sets with all new hardware. Even assembled them dry with out the washers with the same results... maybe mine have been different but they are WAY better than ever before.. I've heard others experience the same binding effect that's why I figured I'd share my experience/results

[Lavaheadache]

I hear ya, I'm not saying that these gears in particular aren't more prone to fitting too tight. I wouldn't doubt it. I was just mentioning that an old trick is to flip those washers over.

[BarHarborBasher]

I noticed that the washers definitely take a beating .. that's what made me decide to give my sun gear full engagement with a custom output shaft... if the sungear handles 6s with the pin barely engaged it should be very stout with full spline engagement..

[Deckard]

Originally Posted by Lavaheadache

I hear ya, I'm not saying that these gears in particular aren't more prone to fitting too tight. I wouldn't doubt it. I was just mentioning that an old trick is to flip those washers over.

Flipped the washer and all was good. I would have lapped the sun gear but I'm losing the desire to work on the YXL like I used to.

Seriously, what's the point of lapping the sun gear when I'm the stupid bearing on the rear axle is going to break again?

I was just about to throw away the broken YXL parts this weekend. I kept them around because at they seemed like cool little trophies. Now they're reminders of the money spent. I think I'll take them to Axial Fest next year and bring my YXL. Maybe the rear driveshaft bearing will blow in front of someone that has the power to at least acknowledge there's an issues.

[Lavaheadache]

I'm glad it worked for you. It's just something I've done in the past and had pretty good results. Obviously the better option would be to replace the washer but sometimes I'm not prepared like that before had and don't want to wait for a part to arrive. I'm getting better at being proactive about having life-saving parts in my tool box though. Definately the side effect of being a yeti xl owner.