Rear Diff Backlash

[Heg87t]

Hey,

Need to double check the backlash on my gears after changing to a posi center section and have a question.

I am concerned now that it is too loose. Really seems like maybe 0.040" slop when I turn the pinion gear but I see that all the procedures read to hold the pinion and measure the movement of the ring gear.

Any one have a good tip or method for holding the pinion still while checking the backlash?

 

[ericttype]

i set new gear up 8 to 12 thousands closer to 8. i use a dial indicator and hold the pinion yoke with my left hand and move the ring with my right, you only need to move it slightly back and forth you will feel it just touch the pinion teeth, try switching the shims side and see what you get 40 is way to much backlash

 

[ericttype]

you need a dial indicator buy one or borrow one maybe you can rent one, dont guess if you want it to last,hope this helps

 

[mikestertwo]

You should have measured the backlash before you pulled the original carrier out. Set it for around .008" That should get you close.

 

[Heg87t]

Yup

You should have measured the backlash before you pulled the original carrier out. Set it for around .008" That should get you close.

Yes I should have but I didn't.

I have an indicator now and will check it. I hope I am overestimating the backlash now. Is it typical that the when you hold the ring and move the pinion gear it looks like more backlash then if you hold the pinion and move the ring?
I think I need to move some shims thickness from right to left. I an sure that I kept them on the correct side during disassembly but could have swaped them.

i set new gear up 8 to 12 thousands closer to 8. i use a dial indicator and hold the pinion yoke with my left hand and move the ring with my right, you only need to move it slightly back and forth you will feel it just touch the pinion teeth, try switching the shims side and see what you get 40 is way to much backlash

Thanks for the tip on holding the pinion. I was looking for some solid way to hold it you are right I don't need to move the ring gear much to check it.

 

[ericttype]

hold the pinion yoke and rock the ring gear back and forth slightly you will get a feel for it. try this link it may help Axle Gear Swap Dial Indicator Measure Backlash Photo

 

[Heg87t]

Is 0.013" too much?

So I got the indicator set-up last night and measured the backlash at 0.020" as it sat. Guess I overestimated a bit.

Pulled the carrier out and measured the shims:
LH (closest to ring gear) 0.235"
RH 0.243"
Total 0.478"

Swapped the shims side to side, reassembled and measured the backlash again and found 0.013". :frown:

I then put in the shims I had from the '76 TA rearend that the posi came from
LH 0.245"
RH 0.233"
Total 0.478"

Put those in and I might have about 0.0125" with those.

Do you guys think that is too much for a used stock ring and pinion?
I tried a couple of parts stores yesterday for gear marking compound and got the blank stare from behind the counter. I will try one in town that is open today.

Anything else to use for marking compound that won't mess up the oil after I am done?

 

[regal81455]

I think you can use prussian blue, maybe someone else will chime in. Maybe a grease pencil would work? As for the shims, unless your bent on getting it done today Ive got alot of shims left over in my master kit from my recent install. You really want to be .008 to .010 from what I was told. And he actually said you want to be .008 fresh so it settles in. Id sell them to you for $25 shipped. If your interested PM me.

 

[ericttype]

So I got the indicator set-up last night and measured the backlash at 0.020" as it sat. Guess I overestimated a bit.

Pulled the carrier out and measured the shims:
LH (closest to ring gear) 0.235"
RH 0.243"
Total 0.478"

Swapped the shims side to side, reassembled and measured the backlash again and found 0.013". :frown:

I then put in the shims I had from the '76 TA rearend that the posi came from
LH 0.245"
RH 0.233"
Total 0.478"

Put those in and I might have about 0.0125" with those.

Do you guys think that is too much for a used stock ring and pinion?
I tried a couple of parts stores yesterday for gear marking compound and got the blank stare from behind the counter. I will try one in town that is open today.

Anything else to use for marking compound that won't mess up the oil after I am done?

if you are just changing to a posi unit and did not change pinion bearing or gear i would not worry about the pattern, you are only swapping out the open carrier for tha posi, try to get it as close to 8 and you can, and when you think it is shimmed right. The carrier should be pretty tight to go in should not just slide it in just by your hand pressure, lets say you got it shimmed to 13 thous and the carrier slides in very easy get a 3 to 5 thous shim and put if on the left side tightning up carrier and backlash with one move, hope this helps good luck

 

[Heg87t]

Thanks Eric. I was thinking about this. I will make a couple of shims tomorrow at work to try out.

 

[ericttype]

i should have a few shims laying around if you want me to send you a few

 

[Heg87t]

Maybe

i should have a few shims laying around if you want me to send you a few

Thanks Eric. I can easily make up a few from shim stock here at work. I was going to try a 0.010" and see if I could get that in the case then recheck the backlash.

 

[Heg87t]

Yeah

I got it to 0.010" backlash by putting 0.015" of shim in the LH side.

Thanks for all the help guys.

Now I just need to get the upper control arm bushings in the ears.

Seems tlike there is always a new challange with this car.

 

[TurboBuRick]

Now I just need to get the upper control arm bushings in the ears.

Seems tlike there is always a new challange with this car.

Get out the bfh.

 

[LOT]

setting back lash

If you have to hold your pinion gear then you don't have enough preload on it.
Should be 10-15 inch pounds. It should stay in place while you move the ring gear back and forth.