Where is Rear diff fill plug

[bora]

Just to double check:

Is the fill plug on the locking diff, on the rearward facing wall of the diff and has a hex head (11 mm or so).

I know the drain plug is right at the bottom of the diff.

I am getting ready to swap out the oil.

Thanks

Bora

[odoh]

Backside facing the spare tire ~ odoh

[Idle_Chatter]

Right where odoh said, the only plug on the diff cover. OBTW - it's 15mm.

[JimWilson]

odoh;

For the locking diff? Are you certain? I just did mine this weekend and it was on the passengers side of the diff, about 4-5 inches from the top.

[csimo]

The Eaton Locker axle has the fill plug facing the rear of the vehicle (includes 2001, 2002, and 2003 models).

The standard axle (non locker) has the fill plug on the side... not the rear.

[odoh]

Jim ~ I've a G80 w/the plug on the back cover. I just recently chkd the level. I didn't bother to go looking for another fill plug. Guess I'll chk around the next time I'm under there. ~ odoh

***** On Edit: Crawled under, have nothing where you spoke of. *******************

[ 07-15-2002: Message edited by: odoh ]</p>

[bora]

Same here,

drain plug at the bottom, fill plug on the rear surface.

[JimWilson]

Well, the plot thickens...

Just this weekend I replaced the rear diff fluid with Amsoil. I removed the fill plug, removed the drain plug, then went inside and had breakfast (in order to get a good drain). 45 minutes later I came back out and knew right off the bat that there wasn't 4 quarts in the drain pan. I reinstalled the drain plug and started to fill it back up, but I could only get 2 oz short of 3 quarts in there before it started to leak out. Uh oh. I put the fill plug back in and took it out for a 10 mile drive. When I got back to my house I checked the level. As soon as I removed the fill plug it started to trickle out again, so I know it's full. Hmmm...

According to my window sticker, and the sales invoice that the dealer has, I've got G80; the Eaton locker. But according to you all I have the standard rear, by virtue of the fact that the fill plug is in the side of the diff. Could it possibly be that the dmax has a different locker then the 6 liter motor does? After all, the torque is quite a bit more for you guys, so perhaps they needed 2 different setups? :confused:

BTW; boy, does that GM rear diff fluid stink! It smells like raw sewage.

[ 07-15-2002: Message edited by: JimWilson ]</p>

[SoMnDMAX]

&gt;&gt;Quote&lt;&lt;

Could it possibly be that the dmax has a different locker then the 6 liter motor does?

&gt;&gt;End Quote&lt;&lt;

Bing!! We have a winner... The 6.0L equipped trucks use a smaller rearend (10.5"?) than the Dmax/8.1L equipped trucks (11.5"). It's a totally different animal. If I'm not mistaken, the 6.0L differential requires just under 3 quarts, whereas the Dmax/8.1L differential requires about 4.

In either case, I do not think the G80 locker option affects drain and fill plug placement. Most likely they are in the same spot regardless of having the locker or not.

[JimWilson]

Well, if what you say is indeed true then I feel a little better; I was able to squeeze just a bit less then 3 quarts into it this weekend. I also bought 80/90 for the front, but since I've only used 4wd for about 30 miles thus far, I didn't swap that (the trucks got 3000 on it now, so that's why I did the rear). Is the front 3 quarts as well?

But is there a way to be certain it's the Eaton (other then the window sticker)? I don't see the words locker or Eaton anywhere on it. You watch, someone is going to suggest doing a smokey burnout and look to see if there's one mark or two... :D :D

[SoMnDMAX]

Jim, look in your glovebox at the "Service Parts Identification" sticker. Scan thru the codes, and if "G80" is listed, you've got the locker. Eaton makes the locker, American Axle manufactures and assembles the housing. All of the locker equipped trucks use the Eaton, regardless of differential size.

I can't remember what the front takes exactly, but if memory serves me correctly, 2.5 quarts is the number that pops into my head.

[Chris N5CWM]

http://www.torquecontrol.eaton.com/prod2.htm

This website has all the info you need! Even some
short video clips on how it works.
Eaton makes the locking diff, called a "Positive
Locking" differential. They are all based on the
same principle, but range in overall size based
on the application. For example, the S-10 sized
pickups get a small unit, the 2500HD gets a much
larger unit but work the same way.

Here are some pictures I took at the Houston
Power Tour a couple years ago:

http://n5cwm.dynip.com/images/g80.html

[ 07-19-2002: Message edited by: Chris N5CWM ]</p>

[bora]

Well

I did it. Just changed the rear diff oil in about 30 minutes.

It took exactly 4 quarts to the fill level.
Got probably about 4 quarts of very black oil
minimal metal, just the black oil. This is with
4K miles and 420 miles of towing 8500 lb trailer.

Put in Mobil1 75W90 synthetic gear oil. I like Redline better but I like the Mobil 1 bottles with the easy fill spout.

Bora