JunJun

As you know, due to its c-clip structure, there is some play in the axle's in-out direction.
In the past, there were several threads about clunking noise due to its excessive play.
I understand that some play is normal, but has anyone succeeded in eliminating the clunking sound by reducing the axle's play, with a new diff, for example?

Any information is welcome!

big gear head

You didn't say what differential you have, so I'm assuming that it's the Auburn. As the cones in the Auburn wear they allow the axle gears to move deeper into the case. This increases the distance between the axle gears and the cross shaft. When this happens it also increases the space between the end of the axle and the cross shaft, which increases the axle end play. With the Auburn the only way to fix it is to replace the differential with something better, like the Eaton Posi.

JunJun

Mine is a stock 10 bolt posi, so it must be auburn.
Yes, I heard there is no way to fix auburn, other than replacing it with another one.
What I want to know is, has anyone actually succeeded in eliminating the play with a new diff and fixing the clunking issue?
This seems to be a very common problem to C clip axle cars (not just thirdgens), but no actual solution can be found on the Internet at all.
Replacement of the diff really solves play and ckunk issues?

big gear head

Yes, replace it and the problem will go away. Eaton Posi, Yukon Dura Grip or Power Trax Grip LS. These are rebuildable and can be shimmed internally, so if the problem comes back you can fix it without replacing the differential again.

JunJun

Thanks for the reply.

I have one question.
For now, my diff is working totally fine, except for the clunking noise.
I still don't understand the structure tha diff, but what will happen if I leave it as it is?
Will it change the backlash of the gears and affect the fundamental functions of a diff in the future?

big gear head

It will work fine until it completely wears out, then it will only spin one tire. The ring & pinion gears will not be affected. The only problem is that as the Auburn wears it fills the rear end with powdered metal, which gets into the bearings.

JunJun

Thanks again.

So I need to do something before it completely wears out.
(I don't like the idea of spreading out the metal powder!)
For now, I'm going to change the diff oil periodically, and check if the play gets larger.

BTW, do you have any recommendation for the viscosity of diff oil?
I just feel a higher viscosity oil can protect diff more, just because, when the diff oil is not warm yet, the clunking noise sounds a bit less loud.

big gear head

No need for anything more than 80W90 in most cases. Just be sure to use the GM limited slip oil additive when you change it.

JunJun

Big gear head,
When replacing the diff, is it possible to replace only the diff?
I talked to my shop and he said axle shafts, rings, pinion gears, and bearings should also be replaced.
What do you think of this?

big gear head

No, all you need is the differential. I'm assuming that you have a 3.23 to 3.73 gear. If you have a 3.08 or 2.73 then you have a problem. The 3.08 and 2.73 use a 2 series differential. The after market differentials are 3 series, so they will not work with your 2.73 or 3.08 gears. If you have a 3.23 to 3.73 then the after market differentials will work fine. Here is how you do it. http://www.nastyz28.com/forum/showthread.php?t=19773

JunJun

I'm not sure about a gear ratio.
If mine is a 2 series diff, what should be replaced other than the diff?

big gear head

You will either have to install another Auburn or change the gears to a 3.23 to 3.73