Changing diff oil on Z/28

[void_kp]

Hey folks,

I've tried searching this forum but I was not able to find the info I am looking for, so here I am so that future users will also be able to find some fresh post on read diff oil change:

1/ can you confirm these are the 2 plugs that are needed (top most is load, bottom is drain): https://imgur.com/a/C7O6OnZ



2/ how many quarts of AC Delco 10-4034 (GM#88862624) are needed? 2.1?

3/ can you confirm it requires a 3/8 square tool?

[void_kp]

in this post they say 1qt: Rear Axle: 75w-90 GM Part No. 88900401, 1 qt.

[1970judge]

Yes those are the plugs, yes it takes a 3/8 ratchet. Albeit a skinny one. .
Correct fluid is 88900401, 1.1ish qts.

https://youtu.be/iB1rgANL-Oo

[void_kp]

thank you!

now I’ve started the quest to find the rubber gaskets for those plugs… seems like auto zone and oreilly don’t have them. they seem a 20mm ID 26mm OD. anyone has luck in finding some replacement ones?

[ariZona28]

It's been a few years but I just reused my old ones. No leaks yet! Also be aware that your diff may thump and clunk a bit during tight turns. This is normal. I suspect the factory adds the limited-slip additive (not required) in the factory fill to reduce customer complaints

[void_kp]

that your diff may thump and clunk a bit during tight turns

yes, and I love it. it’s the sound of a good old mechanical lsd. ppl complaining about that don’t deserve a z/28 ��

[1970judge]

Originally Posted by ariZona28

It's been a few years but I just reused my old ones. No leaks yet! Also be aware that your diff may thump and clunk a bit during tight turns. This is normal. I suspect the factory adds the limited-slip additive (not required) in the factory fill to reduce customer complaints

They didnt, but, there is a TSB from way back and the fix was add it for complainer customers. It will reduce the effectiveness of your diff, so i always advise against it.

[1970judge]

Originally Posted by void_kp

thank you!

now I’ve started the quest to find the rubber gaskets for those plugs… seems like auto zone and oreilly don’t have them. they seem a 20mm ID 26mm OD. anyone has luck in finding some replacement ones?

Never replaced them in my 6 years of ownership.

[CamayroZ]

Rear diff. drain plug washer; Napa P/N: 704-1968
The same ID/OD is used on a couple of other cars and works well.

[void_kp]

Originally Posted by CamayroZ

Rear diff. drain plug washer; Napa P/N: 704-1968
The same ID/OD is used on a couple of other cars and works well.

this is mega helpful, thank you!