8-3/4" rebuild setup bearings

[70dart65coronet]

So i am rebuilding a 8-3/4" that came in my car. i think the original owner broke it, and when it got fixed it wasn't setup correctly. had almost no backlash so the differential would make a horrible noise when cruising. so i got a master rebuild kit with new ring and pinion and crush sleeve eliminator, everything from diff doctor. My differential case and carrier check out good, with in the 3 thousands of run out on the ring gear surface.

i used the original bearings to make setup bearings for pinion depth and bearing preload. I switched to a billet crush sleeve eliminator. got it all set up and everything is great with the setup bearings. 240 lb ft of torque on the pinion nut, with 15 in lb of rotational preload torque. contact tooth pattern looked really good. 8 thousands of back lash.

installed the new bearings on the pinon and had to change it all again...setup bearings didnt even get me close.

I had to change from .015" pre load shims to .029", took 4 trys, had to use the press to push the pinion off the small bearing.

I also have to change the depth of mesh shims. The new ring and pinion calls for a 2.767" checking distance and i had it right on the money with .040" of shims between the big bearing and the pinion using the setup bearings. now i have to pull that bearing off with a special tool so i dont damage it, and take out .008" of shim to get back to the specified distance.

what a PITA, whats the point of making setup bearings if i have to start all over again...

also have to come up with some different selections of shim thicknesses, i think i will have make my own out of shim stock. of is there somewhere i can get shims other than 10, 20 increments?

Any thoughts?

 

[fishy68]

That's because you used old half worn out bearings for setup bearings. You can't do that. The setup bearings also have to be new bearings to mimic the outcome when your installing new bearings

 

[fishy68]

What shims are you needing? The big ones to set the pin depth or the small ones to set the preload?

 

[my68barracuda]

I had always thought the variance that caused the need for the shims was in the case to case machining and that the bearings and races were almost identical from set to set. Your experience differs.
Perhaps the used bearing/race that you used for the setup bearing had a lot of wear?
Can you see or measure a difference between your new bearing and the one used for a setup bearing?

 

[john-9]

So i am rebuilding a 8-3/4" that came in my car. i think the original owner broke it, and when it got fixed it wasn't setup correctly. had almost no backlash so the differential would make a horrible noise when cruising. so i got a master rebuild kit with new ring and pinion and crush sleeve eliminator, everything from diff doctor. My differential case and carrier check out good, with in the 3 thousands of run out on the ring gear surface.

i used the original bearings to make setup bearings for pinion depth and bearing preload. I switched to a billet crush sleeve eliminator. got it all set up and everything is great with the setup bearings. 240 lb ft of torque on the pinion nut, with 15 in lb of rotational preload torque. contact tooth pattern looked really good. 8 thousands of back lash.

installed the new bearings on the pinon and had to change it all again...setup bearings didnt even get me close.

I had to change from .015" pre load shims to .029", took 4 trys, had to use the press to push the pinion off the small bearing.

I also have to change the depth of mesh shims. The new ring and pinion calls for a 2.767" checking distance and i had it right on the money with .040" of shims between the big bearing and the pinion using the setup bearings. now i have to pull that bearing off with a special tool so i dont damage it, and take out .008" of shim to get back to the specified distance.

what a PITA, whats the point of making setup bearings if i have to start all over again...

also have to come up with some different selections of shim thicknesses, i think i will have make my own out of shim stock. of is there somewhere i can get shims other than 10, 20 increments?

Any thoughts?

there is always some variance in bearings and as stated in other posts your used bearings are probably no good.

as for shims for pinion depth and pinion preload you can get them from Ratech Manufacturing directly or thru Summit Racing
489 pinion depth Ratech 1102
742 pinion depth Ratech1108
for the 489 solid spacer you can use pinion bearing preload shims for the 741 and 742 case Ratech 1107