XXXT, gritty diff ???

[ballbreaker]

I rebuilt my tranny the other day after I noticed that the diff was a bit gritty. Since the rebuild, I ran a few packs through it and noticed the grittiness back again. Before I ran it, after the rebuild, it was smooth like butta'. When I took the diff apart the first time it looked like it was perfect, no dirt or wear. I dont run it in loose sand or dusty conditions and the diff is adjusted to spec. I have a backup tranny on hand at all times so down time is minimal. Both are MFE.
***? :confused:

[LasagnaCat]

Did you use new balls or did you just put new rings in (or flip the old ones) using the old balls...? Are you using enough diff lube on the main gear? Are your bearings and/or the tranny case still sealed, all it takes is one little spot for gunk to get in..? Do you have the foam washer on the thrust bearing side? If all the parts are in good physical shape, my guess would just be that you're not putting enough diff lube on. It'll never be as nice after you run it that first time, but it shouldn't be as gritty as it sounds. You are checking and readjusting/tightening the diff as needed during break-in after reassembly, right? And you didn't mention the slipper clutch, if that's not adjusted correct that can be a factor.

[traxxas-dude]

I dont think the slipper clutch wouldmake the diff feel gritty... ;)

[rocknbil]

I've always been a minimalist when it comes to greasing the diff balls, just enough to coat them prevents it from slinging out and getting all over the gears.

Dirt is almost never an issue inside a Losi or AE tranny. It's going to be like Lasagna says, the rings or the balls themselves. Sometimes you **can** get away with the old balls but if they are worn it is immediately apparent on re-assembly even with new rings.

What happens is the near-perfectly round balls get microscopic flat spots on them. Even on brand new rings, this will create that chunky feel. The idea is that with new balls, the rings wear first and if you catch it as soon as you can, you can get away with changing just the rings. Let it go too long and the balls begin to get the flat spots.

There is another possibility, especially if you replaced the balls AND the rings. They shouldn't get chunked up so quickly. If your diff was incorrectly adjusted, or you didn't re-adjust it after the first run or two, the diff balls can slip on the rings and bingo - scratched rings or flat spots on the balls.

[LasagnaCat]

I dont think the slipper clutch wouldmake the diff feel gritty... ;)

If it's incorrectly adjusted (too tight) it can greatly accelerate the wear on the diff parts, causing them to feel gritty sooner than they normally would. If the diff isn't adjusted/tightened during break-in, a slipper that doesn't slip can be killer. Don't forget to think of the big picture.. the drivetrain involves many moving parts that all need to function correctly together to acheive symmetry. One error I see commonly made is when people overtighten the two halves of the tranny case to the point where the entire diff/tranny drags - all it takes is one moving part being off somewhere. :)

And rocknbil, I only mentioned dirt being a potential issue because I've seen far too many people removing the seals in the big bearings on the outdrives. Whether it was well intentioned and they're lost or deformed in a "cleaning" process or to "remove drag," I've heard/seen both. As mentioned it *shouldn't* be an issue, but people do screwy things with these sometimes and if he's running on a weird surface (baseball diamond dirt.. UGH, never again. lol) dirt can sometimes seep in even a small opening like that if given the chance. He does mention there not being dirt in the tranny, just figured I'd throw that out as a general thing and not so much for him specifically :p

[XR Mugen]

Hello !

I have noticed the same issue with the rear ball diff in my XXX-4 and i think I have learned a few things...

1) When rebuilding the diff, just get new balls and rings for it. I have tried to reuse rings by flipping them and a lot of times, it still gets gritty quite quickly... also, make sure you are getting the carbide diff balls instead of the regular ones...

2) The thrust bearing gets really dirty and I do not like the stock XXX-4 thrust bearings as the balls are loose and held in place by grease and the two thrust bearing washers only. I switched to the molded thrust bearing with the carbide balls (LOSA-3098) and it seems to be a lot better.

Good luck.

[RCHavok797]

I know on an Associated vehicle what usually causes the diff to feel gritty is not the diff rings and balls but the thrust balls and washers.

[rocknbil]

Why would that be? My first Stealth tranny was the original white-plastic 10T, I've had several other manifestations of their trucks including the GT's, and I've never experienced that at all.

Don't take this as an opening for an argument, I'm only asking the reasoning.

[Gutter Ball]

Hello !
1) When rebuilding the diff, just get new balls and rings for it. I have tried to reuse rings by flipping them and a lot of times, it still gets gritty quite quickly... also, make sure you are getting the carbide diff balls instead of the regular ones...

Hello to you! I've been using the same set of diff rings for close to 3 years. I just sand them down during each rebuild and they're good as new. Diff balls I replace every time. I get the bulk pack of 100 made by IRS.

[ballbreaker]

Thanks to all for your helpful info. I just ordered new carbide balls for the tranny. Ill see what happens.

[cabbynate]

Try here, http://ourworld.cs.com/hifi09/myhomepage/sale.html
These work great!!!!!!