Im setting up a 9.25 for a friend. Its for a 2018 Ram 1500. What would you consider to be excessive runout on the carrier ? (No Gear installed ) The carrier in question is a new truetrac locker.

I would look at the factory service manual and follow the specs. it provide.
I think the 8 3/4 uses .0030 maximum run out.
I found out by accident that heating the ring gear up to or over 130F and then install it on the carrier really helps making it seat flush eliminating any ring gear to pinion tooth backlash variances :: scope:

Couple thou, tops. I don't even like to see that.

We deburr everything before putting it together. Stuff has been cheapened, Processes streamlined. Edges and bolt holes will have burrs.

I'm checking the carrier without the ring gear attached and I'm getting .003 runout. I was leaning toward having him send it back. Didnt want to go through attaching the gear and trying to get correct backlash if it was going to be a waste of time.

Might want to call the MFR. and ask what their spec is

Backlash will effect the pattern some, not as much as pinion depth. Always a good idea to check BL at multiple spots.

I assume you have the correct side bearing preload and the caps torqued?

I had a 69 fsm sitting here and the 8 1/4 and 9 3/4 both said maximum run out .006. The 9 1/4 was not born yet but I would assume it would be similar.

The 1970 FSM shows .006 Max . Put it together , and then check it . I've had carrier runout before , and after Torquing the massive Ring Gear on , to pull Specs down to the Low side .. Try it , can't hurt . Ronnie

Chuck it in the lathe and true it up..

I have a local guy "true-up" all the Power-Loc 8 3/4 carriers for my customers. For some reason most of them are out by .010 -.015 Maybe lots of gear swaps.

Gus

I’ve worked on many, I don’t believe 10-15 thousands for a second. They would bind up big time at normal backlash…….hogwash.

After bolting on the ring gear the run out came down to .002 . The backlash only varied by .002 as well . I'm happy with that.

Are you SURE you want to run those gears that tight on the back lash?
I wouldn't
What do the instruction call for on the minimum? I wouldn't run the back lash any tighter than what the manufacturer calls for at room temps.
As already pointed out check the back lash in several different locations, I try to check them 90 degrees apart

.002 is the variance. Actual backlash is .007 - .009