I pulled the cover off the differential on the new car to inspect and change the fluid. Fluid came out very dark but the gears look OK it my amateur eye. But here's the issue. Car has posi. Does two tire burnouts no problem. But as I was getting ready to pull the cover, I grabbed one wheel and spun it. The other wheel didn't turn. Sometimes it caught a little but it would quickly stop. Given the very dark fluid and the wheel issue my educated guess is the clutches are wore out. All I need to do is replace the old clutches, correct? Nothing else I should be worrying about when I'm doing that?
I would just put reg 80-90 non LS gear lube in. Alot of people over do it with the LS additive and then the clutches slip but don't chatter. I'd rather have some chatter and then grab when needed.
That unit pictured was one of the better OEM units of that era. However,they were all assembled rather vaguely. It’s likely just as tight or loose as when it was originally built. I can be improved by shimming the clutches tighter together. You can tell this by how much or how little of play you have between the spider gears and side gears. I like to have almost none,but not too tight to the point of binding. When tuned this way,you can also eliminate the preload spring. You will still get traction to both wheels like a posi has,but with little to zero chatter because now the clutches can relax while cornering. This is how I build my clutch style posi units. The new units require good clutches first,which none of them have.
I always say...IF IT AIN'T BROKE...don't fix it. Put the fluid in and run it. If the car ran good leave it alone... Those units are inherently noisy when you heat them up on freeway runs then you get off the freeway and they will chatter in turns. The clutches get glazed like a Trans flywheel and act like two pains of glass with liquid between them.... They will stay adhered until the torsion of the axle then break apart with a violent pop... over and over this will happen. The additive is suppose to help this from happening. too much additive will likely NOT hurt the clutches etc. UNLESS your JUST using additive with out oil...LOL. Good luck on your choice of what to do. Were all not drag racing our cars. A fun burn is good enough from time to time. Jim JD Race
Thanks for the advice guys. I think I will leave it alone and just refill it for now. I will keep an eye on it and do a rebuild when it actually stops working.
