Need help with my Muggy - RC-Monster Forums

Unsullied_Spy · **Need help with my Muggy -** 02.02.2009, 05:53 PM

I've recently had a really bad noise in my front diff. I thought I had stripped the ring and pinion but I pulled it out and it's in immaculate condition. There are no signs of wear, strippage, or slippage on the gears. I checked the wheel bearings, CVDs, wheels and hubs, etc. and everything looks good.

I've got some video showing what it sounded like. In the beginning the diff cup on the front diff pinion was loose, I thread-locked the screw and cranked it down as tight as possible but it that hasn't fixed it.

I took the front wheels off and set it the rear on the ground and hit the throttle a few times and it didn't make the noise.

BrianG · 02.02.2009, 06:36 PM

You said you checked the ring/pinion on the diffs, but did you check the gears INSIDE the diff? If you have lots of power and/or the internal gears aren't shimmed perfectly, you may have sheared the tips off those gears.

Unsullied_Spy · 02.02.2009, 06:48 PM

I checked the diff internals as well, they looked brand new. I'm really stumped on this, everything that I can think of looks like it should run perfectly.

BrianG · 02.02.2009, 07:09 PM

I don't know what to say then. And you're SURE it's coming from the front, and not the center or rear?

Unsullied_Spy · 02.02.2009, 07:12 PM

Yeah, it's the front. I pulled the center diff after the front diff and it was also in great condition. I may pull the front diff again and make sure that the diff cup didn't somehow come loose again but I highly doubt that's possible. It has a notch in the flat spot, I used thread lock (and let it cure), and it's cranked down really tight.

BrianG · 02.02.2009, 07:21 PM

Well, how about removing the front center shaft? That would isolate the center and rear. Of course, this would only work with REALLY thick CD oil...

Metallover · 02.02.2009, 07:34 PM

If you keep running it you'll eventually find out what it is...

Unsullied_Spy · 02.02.2009, 07:40 PM

Quote:

Originally Posted by BrianG

Well, how about removing the front center shaft? That would isolate the center and rear. Of course, this would only work with REALLY thick CD oil...

When the front diff cup came loose it would drive around as RWD (CD would unload a little, but it moved) without the noise, so it's definitely in the front end.

BrianG · 02.02.2009, 08:29 PM

OK then, hook the center shaft back up and remove both of the front CVDs. I know this seems like a lot of work, but the idea is to isolate the exact spot. Of course, you'll still have that unloading issue.

Unsullied_Spy · 02.02.2009, 08:35 PM

OK, I'll give that a shot. I've got the diff apart again right now so it won't be as much work. I plan to remove the front input cup and shim the pinion, it needs a shim (there is a little bit of the pinion not making contact with the ring). The cup is still on pretty tight well though, despite the screw being out.

BrianG · 02.02.2009, 08:36 PM

I know this is a lot of work, but without being there, it's tough to say. Just going through the thought process I would be doing...

Unsullied_Spy · 02.02.2009, 08:48 PM

A lot of work yes, but worth it if I can get it working again. I ordered a new pinion gear for the diff, I think mine may be twisted a little.

bdebde · 02.03.2009, 12:58 AM

Check the bearings on the diff pinion. My muggy wears them out bad enough to where the bearing has enough slop to allow the gears to slip by each other.

Unsullied_Spy · 02.03.2009, 01:32 AM

The bearings feel pretty good. The inner wheel bearings are the worst in the whole truck and they aren't even notchy. I checked them the other day and they have some resistance to them but it's tolerable. If you say it happens to you though that's good enough for me. I've got plenty of spare 8x16 or whatever the pinion bearings are. I'll give it a shot and see if it helps.

Unsullied_Spy · 02.05.2009, 02:03 AM

I wriggled the input cup around while the case was still assembled and couldn't help but notice a crack going about half the way around where the ring gear goes

I'm going to pick up 2 aluminum cases (front and rear) and make sure the pinions are all shimmed and put it back together. I'm hoping to get by with the ring and pinion I have now though I have a new pinion coming just in case. Thanks for the help guys!