Installing Eaton TruTrac

[Dbunch9]

If I have a 1le diff with a stock carrier, can I just swap in an Eaton and keep all the same shims? Or do I need to remeasure the pinion depth and backlash? Seems to me like nothing should change if I use the same factory ring and pinion

[Black_SS10]

Yes. But I would still measure everything and check the pattern to be absolutely sure.

[cdb95z28]

The pinion depth isn't going to change. That is determined by the crush collar, pinion bearings, pinion shims and pinion shaft. You need a special tool to check pinion depth.

Hopefully nothing else will change for the worse.

Before you start disassembling the internals, check the OE backlash, tooth pattern and break-away torque as these can change.
I'm sure you are installing new carrier bearings, so this will definitely change the break-away torque, but IIRC the service manual lists a new vs old bearing breakaway torque #. Break-away torque is a measurement of how tight the diff spins in the bearings. Old bearings will allow the diff to spin more easily than with new ones as the old ones will break in over time.

If the service manual is only listing the pinion bearing torque, then atleast you'll have some kind of data on what the OE torque was with used bearings.

I reused the OE shims when I did the TrueTrac install. The hardest part is getting the TrueTrac and shims back in the case. The service manual calls for using a case spreader to make the diff come out and go in easily, but good luck finding one. Make sure you ID which shims came from which side. If you mix them up this could change the pattern and backlash. Same goes for the bearing caps.

Once installed, check your tooth pattern by using gear marking compound or Prussian Blue paste. compare the new pattern with the old and see if it falls within the recommended patterns.

Check your backlash to see if it is still in spec.

After my install, everything was in spec. The gear contact pattern actually got better. I track my car, and the new Truetrac diff worked great last summer with no problems.

[gtstorey]

Originally Posted by cdb95z28

The service manual calls for using a case spreader to make the diff come out and go in easily, but good luck finding one.

There are diy case spreaders online that you can build fairly easily, but I have no idea how necessary or useful they are.

[Black_SS10]

A vice/press and or a prybar works too.

[Dbunch9]

Is a case spreader exactly what it sounds like? Something to push the sides apart so the carrier can come out?

[cdb95z28]

Originally Posted by Dbunch9

Is a case spreader exactly what it sounds like? Something to push the sides apart so the carrier can come out?

Yes. It doesn’t take much spread to get it out.

[oldman14ss]

would someone give guidance on where to find the web page for that spreader or just google it

[gtstorey]

Originally Posted by oldman14ss

would someone give guidance on where to find the web page for that spreader or just google it

https://www.jeepforum.com/forum/f37/.../#post11062289

or google "diy differential case spreader" will pop up several videos.

[cdb95z28]

The GM service manual specs the max amount of case spread at .040"

New bearing torque is 19-27 lbs/in
Old bearing torque is 9-20 lbs/in

Backlash spec is .002-.005", measured in three equidistant spots with a max difference of .002".

Mine was .0045 OE, .003 after TrueTrac install
With the old pinion bearings and new carrier bearings, my breakaway (rotational) torque was 14 lbs/in
My pattern moved down towards the toe of the teeth, which is good as it looked like a "competition" pattern that many ring and pinion manufacturers look for on heavily loaded assemblies.

[Dbunch9]

Awesome thanks for the help guys!