I have 8000 mi on my GMC with D/max & Allison T. with limited slip rear end. How important is it to change the fluid in the rear end? My GM dealer said I did not need to change until 25,000 mi. I tow a 5th wheel thats 12,000 lbs.

Change it NOW! I run mobil 1, or you could run the factory grape juice or other options

I would also change the fluid in the front at this time. Run the same fluid in the front as the back(synthetic).

Also change the alli spin filter if you havent and dont forget about the round filter magnet.

Thanks for your help.

How hard was it?

Any hints/tips?

What fluid did you us and where did you get it from?

I am going to do it on sunday.

Not hard at all, drain plug is on the bottom of the diff. Drop the spare and you've got plenty of room to tip the bottles up for re-fill or just get a pump to fit your bottles. I used Mobil 1 in mine but Red Line, Royal Purple and Amsoil GL 5 rated oils are what a lot of others are using, along with the GM "Grape Juice".

On a scale of 1-10 of easyness, this is somewhere between 0 and 1. If your truck is like mine was you will be amazed at the amount of crud on the drain plug. Plus you may find the amount of oil in the rear diff a little low from the factory. I didn't drop the spare and didn't have one of those little plastic pumps. Just squirted it in via a short piece of clear tubing. The good feeling I had was worth the price of the Mobil 1

You Guys Actually Change The Rear End Fluid At 5000 Miles????i Have The Stock Rear End And 7800 Miles, I Dont Plan To Change It Soon,why Should I?????????

Because everyone who has changed it early has noted the SIGNIFICANT amount of break-in material in the lube and on the drain plug when they drained. That said, to each their own as it's your truck.

Hound ............speaks the truth!! I changed mine at 2500 mi, sure glad I did. Front was low, and back was pitch black. Used mobil 1 75-90 syn. Easy piece of mind task..........Rick p.s. now I will wait 25,000 mi.

I changed mine out at 250 mi. again at 2000 mi. and again at 5000 mi. After the first change, seeing the crud on the magnet and the crud in the oil I was not going to let that spendy rear end take a beating! Just changed it out this weekend with 60000 on the truck, I also use 75w90 mobile 1.

1) What tool did you use to get the plug out.

2) Size of tool metrick or standard.

3) And how much did the diff. take.


Jim

i have 80k on mine and never changed. Dealer said dont worry about it until 100k

1) What tool did you use to get the plug out. If I remember correctly, its a standard 3/8" or 1/2" square recess.

2) Size of tool metrick or standard. Std

3) And how much did the diff. take. Four quarts. The factory fill is typically light at 2 quarts


Jim
.

It takes a 3/8 inch socket extension. BigRedD/A.

:eek: your dealer wants to do most of the work on your truck out of warranty :( i would find another dealer



i have 80k on mine and never changed. Dealer said dont worry about it until 100k