Uneven Pinion Thickness?

[attackoftheclone]

So i got new 3.73 gears from frpp, and as im measuring and comparing pinion head thickness to the old set up, i find my new pinion has .007 difference in height, sitting on the face, measuring on the bearing surface with a height guage (1.877-1.885). the old pinion is 1.880
I know it probably has to do with the face not being machined flat, but im wonderin what i should use as a base to set my shim thickness. Max, min, or middle? Any suggestions?

 

[Bullitt347]

If you are reusing the carrier, then the original shims will work 95% of the time. If you are swapping out carriers then you are probably going to have to change shims to make it work.

 

[84Ttop]

I always start with a similar thickness pinion shim when setting depth. I have a pinion bearing set that has been honed, I use this just for gear setup so I don't have to press a bearing on and off a few times to get pinon depth right. The 30 some dollars I've spent on a spare set of bearings and a few minutes to hone them has paid off in hours saved during setup

 

[attackoftheclone]

If you are reusing the carrier, then the original shims will work 95% of the time. If you are swapping out carriers then you are probably going to have to change shims to make it work.

I am changing my carrier to an eaton tru-trac. Does the carrier really make a big difference in pinion depth?
And side note: what fluid should i use for that style locker? ( gear driven )

I always start with a similar thickness pinion shim when setting depth. I have a pinion bearing set that has been honed, I use this just for gear setup so I don't have to press a bearing on and off a few times to get pinon depth right. The 30 some dollars I've spent on a spare set of bearings and a few minutes to hone them has paid off in hours saved during setup

would it be acceptable to lightly face off the pinion in a lathe to try amd get a true reading?

 

[84Ttop]

I would use a 75w90 standard gear lube with a friction modifier, stay away from synthetic's for sure.
I also wouldn't be concerned with the variation on the face of the pinion, it's hardly worth the trouble to face the gear set. You will see how well your setup is when you check the pattern upon completion

 

[Bullitt347]

I am changing my carrier to an eaton tru-trac. Does the carrier really make a big difference in pinion depth?

It has been my experience over the years that any time you change the carrier you usually end up chasing the shims to get the pattern and backlash correct. There is enough production tolerance difference between the carrier that was originally in your differential and the aftermarket part that the original shim stack will not be correct. You may get lucky with the original shims, but I give it 1 chance in 50 that it will set up correctly with the original shims.

 

[attackoftheclone]

I would use a 75w90 standard gear lube with a friction modifier, stay away from synthetic's for sure.
I also wouldn't be concerned with the variation on the face of the pinion, it's hardly worth the trouble to face the gear set. You will see how well your setup is when you check the pattern upon completion

Yah ill just shoot for the middle of the two and hope for the best.
I read somwhere once in a book not to use friction modifier because theres no clutches in gear lockers??? And i may have misspoke earlier, its a trac-lok (eaton locker) not a tru-trac (ford locker)

It has been my experience over the years that any time you change the carrier you usually end up chasing the shims to get the pattern and backlash correct. There is enough production tolerance difference between the carrier that was originally in your differential and the aftermarket part that the original shim stack will not be correct. You may get lucky with the original shims, but I give it 1 chance in 50 that it will set up correctly with the original shims.

Im not worried so much about the backlash, thats easy to set with an indicator, as long as the wear patter looks good while in the tolerance of backlash.
But the real question is, is there a different tolerance between a gear locker and factory?

 

[84Ttop]

I've always used a friction modifier in the Eaton units without trouble. If the directions for the locker say otherwise then I guess I've been lucky all these years lol

 

[Bullitt347]

Im not worried so much about the backlash, thats easy to set with an indicator, as long as the wear patter looks good while in the tolerance of backlash.
But the real question is, is there a different tolerance between a gear locker and factory?

The backlash is checked with a dial indicator. The backlash is changed/adjusted by changing the shim stack of the carrier left to right or vice versa.

 

[attackoftheclone]

I've always used a friction modifier in the Eaton units without trouble. If the directions for the locker say otherwise then I guess I've been lucky all these years lol

Ok cool. i guess if it was that critical id find alot more fluids for gear lockers.

The backlash is checked with a dial indicator. The backlash is changed/adjusted by changing the shim stack of the carrier left to right or vice versa.

Right, that involves taking just the carrier out and in, till you and your dial indicator agree,no biggie.