HELP GM 8.5 axle rebuild... Will this run?

[Bonnewagon]

If you can read all that and not get a headache- you are not human. See those factory tools referenced? I have the whole set. And it is STILL a job and a half to get it all correct. But like I said, I used to do it with a feeler gauge and a torque wrench. Kudos for posting that!!!

 

[doood]

When you're measuring rotational torque -be sure to not have the pinion seal installed.



That is to assume he's using a solid spacer and not a sleeve right?

If you can read all that and not get a headache- you are not human. See those factory tools referenced? I have the whole set. And it is STILL a job and a half to get it all correct. But like I said, I used to do it with a feeler gauge and a torque wrench. Kudos for posting that!!!

I do believe he has the pinion depth basically correct per his original post. He's pretty much done. I wonder if he put new races in

 

[64nailhead]

doood

Rotational torque is only measuring the amount of torque required to spin the 4 bearings, not the seal. And the pinion bearing definitely needs to be torqued with either the crush sleeve or solid pinion shim. When I've used a crush sleeve and measuring rotational torque I've always used the original (already crushed) sleeve. Then after I'm completely happy with the setup, install a new sleeve set to appropriate crush, recheck rotational torque, then mark yoke nut on pinion shaft. Then lastly remove yoke and install seal, and tighten pinion nut back to position it was in during the last step.

The most important part of the setup is the carrier preload and gear pattern. If you recheck the pinion after a couple of really hard hits and you find it minorly loose, then tighten as needed. I should mention, this has worked for me.

I'll add that I used to be way more anal retentive about making everything perfect than I am now. It just can't be too tight anywhere. Then re-check pinion tightness like I described above. And I don't use this method for 300-400hp daily drivers, but rather something that makes a little more go than that.

 

[Bonnewagon]

he has the pinion depth basically correct

Like I said, if you go by the original pinion shim, it is always very close, maybe a thousandths or two off. I feel it is because it is relatively easy machining the pinion bearing surfaces on the carrier. A straight shot and you can be fairly precises. . But the side bearing surfaces are way harder to get at with grinder tool. Plus you have to accommodate a large range of ring and pinion combinations. You need room for that so the side shims are so thick compared to the pinion shim.

 

[64nailhead]

I don't know what the proper term of it is, but the shim kit made by Motive Gear that utilizes a 2 piece assembly (for each side)for the carrier shims is my preferred choice.

Differential Carrier Shim Kit

Where to buy

www.motivegear.com

This can be found on Amazon, Ebay, Summit, Jegs. It's easy to adjust with minor changes of .002-.004"

 

[Bonnewagon]

That is one of the better kits. You really need a large selection of shims. I remember doing a 1979 LaSabre rear. We needed two kits to get it right. I forget which brand it was but there was just not enough of the thicker shims to fill the space. IIRC it was a kit that came with the 3:42 gear set.

 

[doood]

compiled the shop manuals into a pdf. will be doing a 7.5 this month.

 

[FluoFerret]

Hey guys!
Sorry for my silence these past weeks, but I went through some family sh...enenigans, and I barely got time to go online.

First of all, thank you so much for all of your precious tipps and input. It gave me the strength and will to resume the work yesterday night!
The good news, I have re-assembled everything. Here is the situation as of today:

1. Pinion is at the perfect depth after having the Yukon-Tool at my disposal.
2. The crush sleeve was installed, the pinion assembly requires +/- 14 inch-pound of rotational torque. Preload should be good then.
3. The differential carrier is back in, and indeed needs to be yanked out with a little force. Just liftink it out is not possible, you would just lift the whole axle housing with it, and still not get it out half way. The driver-side shim-pack needed gentle taps with a rubber hamnmer to slip in.
4. Perfect gear backlash according to the gear manufacturer is 0.006 inch, I got it on 0.005511 inch. Swapping shims would increase to 0.008.
5. Overall torque needed on the pinion to rotate the entire differential w/o axles is now 16 to 18 inch pounds.
6. A last check on the pattern, and I get the following results:

Considering that everything is new, except for the housing, I think this might work. Especially since the car is never going to see a racetrack, and rarely any highway. Especially not for the first 500 miles...

What do you think of this? Should I go with a little more backlash or is the measured one still acceptable for what the manufacturer requires?

 

[doood]

Pattern looks good for sure