Changing differential fluids

[Chingon]

Besides oil, what else do I need?
A gasket?
How much fluid do I need?
Thanks

[farmtruc]

You'll need the posi fluid, napa has some. It's like anti friction fluid or something to help the posi clutches operate correctly.
Ya, i a gasket
I would get three of those rear end fluid bottles just to be sure, if i remember correctly two will be fine also. I forgot how much fluid comes on those bottles, but they are the tall skinny ones. No need for synthetic fluid either, just some good 90W fluid will do.

Other than that you're set,


good luck,

allen

[Chingon]

Cool thanks.
I don't know if you know, but on my 01 is there a drain plug? And where is the hole to fill it? Same hole?
Do I need some sort of pump to get it in there?
How do I mix the oil and additive, in a separate bottle?
My buddy at the GM dept. said they dont make gaskets anymore, they just use some sealant or something.
Should Pep Boys or another place have the gasket?
Thanks

[GMCwantsLS1]

It is cool that your diff has a drainplug!! Better buy three quarts of fluid just to be sure. There is a fill plug on the side up a little more that half way up one side of your diff probally has a 3/8 square hole to remove it use a 3/8 rachet with a short extention. Fill with the additave first then the rest gear oil. Check your owners manual for propper fill level. There is usally enough room to squeeze the bottle and get it to go inor you can buy a pump from the autoparts store or attach a hose to the end of the bottle. The fluid will have a short screw on end like a tube of caulk. I've used gasket sealer to put the cover back on but if you have a drain plug that you won't have to take off the cover. I've never replaced the fluid on the newer trucks so if anyone has any thing else to add! Oh and always take out the fill plug first, it sucks if you take out the old fluid and then can't fill it with new fluid (been there done that hahaha). check this http://www.gm-trucks.com/IAR_RearDifffluid.shtml

[farmtruc]

good info gmc!!

i need to get new cover with a plug someday too,



later,

allen

[Chingon]

Originally posted by GMCwantsLS1@Jul 1 2003, 04:50 PM
Oh and always take out the fill plug first, it sucks if you take out the old fluid and then can't fill it with new fluid (been there done that hahaha).

So lemme get this straight, if you remove the drain plug and drain out the oil, you won't be able to take off the fill plug on top?
I'm not sure I understand that part....what did you do since you couldn't fill it with new fluid?

[GMCwantsLS1]

if the fill plug is stuck and you don't know that until you drained the old fluid out then you can't put the new fluid in.

[Chingon]

So then what did you do?

[GMCwantsLS1]

I've heated them with a torch a couple of times and was able to get them loose. A couple times I've fixed rounded off plugs by welding a nut to the outside ot the plug and backing them out with a wrench. Only once I had to drill one out and retap it.

[Chingon]

Well, changed the fluid. I didn't take the cover off and replace the gasket. Call me lazy. It was hot out and after loosening one bolt I was like, "fuck this, I ain't doing 9 more."
Plus the gasket and the inside was replaced and cleaned 500 miles ago with the posi and gear install, so I just drained and filled the fluids.
The drain plug was easy to loosen, but the fill plug was a bitch. I know the torque spec is 15ft/lbs, but I just tightened it as hard as I could, I used a hollow pipe around the wrench for leverage.
I bought a fluid pump at Pep Boys, glad I did that because there's no way you can just pour it in from the bottle.
How often should I change and replace the gasket and fluids? 15k miles or about every 3 oil changes?