This is for an '91 IFS V6 with Truetrac.

About a week ago I found out that my diff breather was missing. I drained the diff and found that the oil was black and watery. I replaced and breather and refilled the diff with fresh oil, then went to Tahuya the next day. I was only able to stay on the trails for a few hours, because my front end was making a horrible noise, metal-on-metal grinding/scraping noise is the best way I can describe it.

I pulled and drained the diff yesterday. The oil was completely black, after only one day of use. I pulled the cover off and degreased the inside. After degreasing, the pinion bearing seems to be awfully loud when I rotate the pinion. The wear pattern on the ring teeth seems to be off too, but I haven't checked it with marker stuff yet, since I don't have any. The pattern seems to be toward the inside of the ring, way inside, but also inconsistent. Some teeth the pattern is clear, others not so much. To me, this all would indicate a bad pinion bearing, probably destroyed by the water and rust. I also have not checked any specs with a dial indicator yet, but I'll rent one in the next day or so to do that too. I have not yet pulled the ring out because I want to test the patterns first.

Any other suggestions? Does it sound like I am going down the right path? I would also appreciate if someone can post the front end specs, backlash, etc, for me. Everything I find is for the 8" diffs, I don't know whether they are the same.

 

I would recommend you take your third member to a shop that installs lots of gears and traction aids and pay them to fix the pinion bearing/crush sleeve properly. Hopefully you stopped using it before you did major damage. This way it's done right, done quickly, and you don't have to worry if you did it right and will get stranded again...

 

Well, the Truetrac is trashed. Their service department told me to try and turn the axles in opposite directions, that if they did not turn the inner gears were either frozen together or broken. In neither case is the unit rebuildable. I guess 35" tires maybe were too much for it, or maybe it was just the water buit up inside. So, looks like I'll take it apart myself, clean out any broken pieces, then maybe weld it together like a Lincoln locker, or just replace it with an open diff and weld that.