anybody have any step by step on changing the rear diff fluid, no pictures necessary, words should do.

This might help:

http://dieselplace.com/forum/showthread.php?t=1858&highlight=changing+rear+diff+fluid


LATER!

I too am trying to learn how to change the rear diff. From what I have read, below should be a summary of what needs to be done. If someone could validate this I would be grateful.

1. Loosen/remove fill plug on back of diff with a 15mm socket
2. Remove the drain plug with a 3/8 ratchet and drain.
3. replace drain plug.
4. Fill diff using a small pump(like for a boat lower unit) with Mobil-1 synthetic gear lub SAE75-90($8) or GM lub($24). Rear diff hold 4 quarts.
5. Replace filler plug.

Sounds right. You will get a better drain if fluid is warm. I did mine last weekend @ 5000 miles. It was filthy enough to make me wish I had done it sooner. The pump is Amsoil # G2039, basically a ketchup pump and hose that fits our qt, gal and 2.5 gal containers. I used Amsoil Severe Gear 75w90 synthetic #SVG-QT.

I.Also want to change my rear diff lube/mobil-1 synthetic. But dont you have to add a additive cuz of the locking diff?

Are there any gaskets or o-rings to replace?

Are there any gaskets or o-rings to replace?



If you just pull the drain plug, there are no gaskets to replace. Personally I prefer to pull the cover at least once just to get a look at the insides of the diff. That is what I am planning to do with mine, but I haven't needed to change the fluid yet (46 miles !).

Also, Mobil/Synthetics should have the additive required.

Just my .02 and I'm a newbie so I'll let it go for .01 !

yeah i figured on dropping the cover too. i probably should have changed the fluid when i bought the truck but didnt do it. what should the fluid look like when it comes out?

Did this yesterday and used Amsoil extended life synth 75w90. Took less than 30 minutes (drain and refill only - didn't remove cover). Mine old fluid came out blackish, and strangely had that grape smell that I've read about here. Funny stuff...

Did mine today, used Valvoline syn 75-90. Very easy todo, took about 20 minutes.

I was able to fill the rear diff without using any kind of pump or hose. I emptyed 3/4 of each bottle into the diff, then combined all four bottles into one. I sqeezed/crushed the last bottle and got all but 1oz out. Im figuring missing 1 oz wont hurt since I only drained 3 qts of the old stuff out.

One thing I did find strange was the drain plug. The diff plug screwed in by hand 6-8 turns tighten all at once with a wrench. I guess I expected it to slowly tighten(like a oil pan plug). What keep is plug from coming loose???

Interesting, only 3 quarts came out of mine also. I was approximately 1" down from fill hole prior to draining the rear axle. Is the factory fill short?

My rear and front diffs both were low from the factory. Engine was a couple notches below full, and tranny was on the low end of the acceptable range too. I took delivery with 7 miles on the odometer as well, so it is not like it had been driven much.

Anyone who buys a new truck should check the diff fluids. It's a known problem that GM doesn't always fill them up all the way. I changed mine before 2K miles and again at 20K miles. The 2K change the fluid was black and nasty. The 20K change the fluid looked like it was new. I think GM uses a break-in additive from the factory in the units along with the break in of the Eaton locker. I could be wrong. Also when changing the fluid the drain plug is also a magnet so make sure you clean it off before re-installing it.

You guys should do asearch of the site about rear diff oil.

Most of the early trucks reported the levels low from the factory.
And with a lot of complaints the procedure for checking the rear lube changed, instead of filling till the fluid leaks back out the fill hole, there is now a measurement that puts the fluid level below the fill hole.

the procedure changed some time in 04 I think and I don't remember exatly the measurement but if you search for it it's here somewhere.

DD

.

I have 6,000 miles on my should i change rear diff only or do front diff too, but was not driven in 4x4 yet? what about transfer case? and trany oil, this is first new truck i owned, last one was used, so i change everything when i bout the truck,

Yes change it.

The rear's are notoruios for coming low from the factory, and the fron't oil usually looks like crap too, and it wouldn't hurt to do the transfecase too.

That will keep you busy tomm. :grd:

DD

.