Hi all,

I have an '03 Express 1500. Had a wheel rear wheel bearing go bad, and decided to upgrade my open diff to the OE posi differential (that I used to have in my previous Express, and made a huge difference in the winter) while I was in there.

I tried to get OE 'GM' bearings, but ended up getting National brand instead. Being an OE GM part I assumed that I could rely on the same factory shims that were in there. Is that a reasonable assumption? It definitely came out easier than it went in, but all I had to do was some light tapping on the left shim to get it to go in. Maybe that's just what happens as things settle over 250k miles? I am waiting on some gear marking compound to arrive so I can sanity check that before closing things up. Backlash checks out ok at ~0.009".

I had to 'estimate' 65ftlbs for the ring gear as best I could because my torque wrench does nor work backwards. If anything I have to assume I went beyond, but uniform, and not 'absurd'. I got a feel for what 65 lbs felt clockwise, and then just estimated in reverse. How paranoid should I be about getting that exactly on spec?

There was no thread locker on the original bolts, so I did not bother putting any on. Should I go back and make sure to do that?

If I need to loosen and re-torque, can I do that with the ring gear in the car or am I at risk of damaging something? 65 lbs seems like a drop in the bucket compared to what that diff is used to seeing, so I'd imagine it's fine.

Most importantly: with the car in neutral, when I rotate the driveshaft clockwise, I have very little friction. When I rotate backwards, there is a fair bit more resistance to motion (still totally rotatable by hand). I would have expected it to be the same in both directions. I'm not sure if this is a result of the posi diff, if it was the same with my old open diff, or if maybe I have some gear engagement issue that I am witnessing. Any opinions?

Taking my time with this, since getting anything wrong is bad news.

Thanks for any feedback,

Karl

 

Did you check backlash before you pulled it all apart? If you put it back together with the same backlash you shouldn't need to check the pattern.

I'd put loctite in there if it was me. If you do it assembled make sure you clean all the oil out of the threads loctite doesn't stick to oil.