[JPhil]

Gary,
I'm putting this in public instead of a PM because I think others will be interested too.

When you set up a posi with shims instead of spring plates, as the clutch plates wear wouldn't that loosen up the clutches and reduce their effectiveness over time?
They may not wear much, but if we are shimming to .003", it would not take much wear to open that up and leave the plates loose....
???

John

 

[gtr1999]

Gary,
I'm putting this in public instead of a PM because I think others will be interested too.

When you set up a posi with shims instead of spring plates, as the clutch plates wear wouldn't that loosen up the clutches and reduce their effectiveness over time?
They may not wear much, but if we are shimming to .003", it would not take much wear to open that up and leave the plates loose....
???

John

I was concerned about that as well doing my first setup. I took my 100k+ mile 69 diff apart and mic'd the clutches. They were still in decent shape and had very little wear on them, maybe .0005-.001".This was with the 4 spring setup,almost 30 years of use.

With the springless setup you have less wear because the constant pressure from the springs is not there. The stock units are all over the place for play. Many times the yokes are blamed for 020-030 endplay only to find out the play is in the clutch shimming. The constant force from the 400 ft/lb springs will give you posi but also increase wear, snowflake clutch breakage, and hammering around corners. I have not had one unit hammer yet and they all have posi action.

I shim them until hand rotation binds, then I back off .005" and check. Once I get the range within .005" I'll grind shims to get the feel where I want it- just short of binding. That is where I set them to.

The differential my son pushed until it blew up was setup like this as well. There was no wear on the clutches when I checked them. That is 8-10k miles of very hard use- drag strip, and 200' burnouts through all 4 gears.

You'll notice the bearing caps and the SHCS I used also did not fail.