FLM Diffs.... rough spot
 

Can't seem to get these diffs to roll smooth... I've taken them apart several times.

There seems to be a rough spot (as if the cup is not sitting square with gear). I have been trying to break them in with my drill but no luck.

Anyone else had this problem with FLM diffs?

http://i35.photobucket.com/albums/d1.../IM001859a.jpg

I already had the truck assembled but never got around to breaking in the diffs... figured I would check them again and they were rougher than I originally thought... now I'm getting frustrated cause I still have to deal with the front diff.

http://i35.photobucket.com/albums/d1.../IM001990a.jpg

Check the bottom of the main gear for burrs/deforming.

the M2 hole is made M3, and the hole is countersunk again, which takes a lot of pressure because of the hardness of the steel. This might have deformed the material slightly causing it to bind at every turn. (in other words, the gear isn't flush with the case) perhaps there are burs on the cup itself?

or is the problem inner gear related? In this case; check if the pin that holds the two floating gears is loose in the case, with some of the diffs you need to dremel a round spot to the end of the small shaft that holds these two floating gears.

You did cross-tightened the screws?

I have dissassembled the cups many times and tried cleaning the surface where the cup meets the main gear. Burs in the cup are all gone (there was even some in the screw holes). This was on both diffs.

The Inner gears have slight play, so I ruled that out. i already grinded the pins so they slide in snug and sit all the way in.

I did attempt to cross tighten the diffs.... tried different ways and it did improve it quite abit... but there's still that rough spot that bothers me.

are the internal or external gears giving you issues?

External... gear and pinion. It is apparent it's gear related because the rough spot is at exactly the same point... but when I inspect the gear it seems fine.

This is what I'm talking about.

http://i35.photobucket.com/albums/d1.../IM001991a.jpg

You did shimm them in the right way? allmost all diffs have got this problem, because it's a 90 degree connection. It's not the most ideal way for gears.

It takes a perfectly flat diffcup, and a perfect gear to make it good, but it seems rather hard to make such a thing.

nis720,

Did you get that "gear" problem figured out? If not, I may be able to help.

Shayne

Not completely... I kep messing with it and tried rotating the cup on the gear and it the rough spot is still there. I kept turning it with my drill (break them in) and it helped abit but it's still there.

I had the same problem. It turned out to be a mesh problem. I ended up putting 2 shims on one side and 1 on the other. I also have the Integy cases and they are a bit of a pain to install. It took me 2 whole nights of troubleshooting to find a sweet spot. Have you tried any shim combinations yet?

The only problem I could actually diagnos was the center drive gear was "sliding" into the gear case just enough to put everything in a bind. At first, it was completely locked in place. Then, I began to mess with the shims trying out different combinations until the mesh just felt right. After several, and I mean SEVERAL attempts, I finally got it.

How old are your spider gears? They may be worn just enough to cause a problem too.

Just a quick question, did you put those paper shims on the cup and gear part to hold the oil and such in? That will help it sit more even on the cup itself.