Thinking about going to posi before I do any major performance mods to the truck. I have replaced these parts in an old Mustang SVO a while back so the work is not what I am worried about. What I need to know is if I get an Eaton or High perf Auburn posi unit will I need to set the gears engagement back up if the ring gear rides at the same point relative to the end bearings as the stocker. I am asuming I can use my original ring gear, nothing wrong with it. When I did the Mustang I had I inspected the original parts and compared them to the replacements and they were within .001" of each other from end bearing to ring gear surfaces. I never got to drive the car again as it was sold before I got the motor back into it. It seemed to work fine when I had it on stands but obviosly there was no load on it to really tell. So if all the numbers add up do you really need to reset the pinion gear?

 

Just measure backlash before you remove pig. Record end preload amount on old carrier bearings setup. Move parts to new carrier and set the correct amount of backlash then add the preload amount diveided equaly to bothe side of carrier. It is a wise idea to replace ring gear bolts too.

 

Anyone know the spec from GM for backlash so i would know if it was even right from the factory?
Thanks.

 

About 4 to 9 thousands is the range with about 6 to 7 ideal for a 10 bolt, BUT when you reinstall it you want to set the same backlash it has now to keep wear patern and noise the same.

 

Good to know you have to be the same, only makes sense I guess. Now lets say my backlash was high or low from the factory and I want it more in the middle, does this mean I should get a new ring and pinion?

 

i dont think a whole new ring and pinion is needed to be able to set backlash on the diff. you should be able to do it with shims and preload.

 

If you change the backlash setting of a worn in gear you will change the contact pattern and posibly the noise level as well. Unless it is noisy now it is best to reset the gear to the same backlash you found (even if it is out of limits) with new pig in it and old gears.