i noticed the rear end is all rusty and paint all burned off. i pull a trailier but 2 bubbies of mine have same year truck and are pulling alot bigger trailers. is the rear housing of rear end getting hot on your truck?

drain and replace with 4 quarts of synthetic

What is hot? If you can grab onto the housing after a good tow, there's nothing to worry about.

i noticed the rear end is all rusty and paint all burned off. i pull a trailier but 2 bubbies of mine have same year truck and are pulling alot bigger trailers. is the rear housing of rear end getting hot on your truck?

As nosliw says, change your fluid and replace with synthetic and do it soon. If it truly burned the paint off then the fluid is probably toast and is going to smell really, really bad. Get all of the old fluid you can out by draining the tubes as well by raising one side higher then the opposite side then reverse. You get a little more this way.

stumo

If you've never checked it, most are factory filled very low..... mine was a quart and a half low......

2 quarts of THICK BLACK nastyness came out of mine

2 qts low for me. Also make sure the vent tube isn't pinched off with a washer like a few others have found.

i noticed the rear end is all rusty and paint all burned off. i pull a trailier but 2 bubbies of mine have same year truck and are pulling alot bigger trailers. is the rear housing of rear end getting hot on your truck?

Yep, sounds like low fluid level causing too much friction, drain and re-fill w/ 4-qts synthetic fluid. You might tell your "bubbies" (?) to do the same, or at least chech the level. Finally what year model do you have? Your signature is missing.:D

Recommended Differential break in has been;

No towing till 500 miles
Once 500 miles are achieved drain and refill
I would recommend pulling cover to flush all break in material and replenish with a synthetic fluid.


If your truck is 4x4 I would recommend doing the front differential too.

Yup, my truck has 6500 miles on it. I checked the rear end yesterday and it was 1 1/2 quarts low on lube. Filled it up with Mobil 1.

Yup, my truck has 6500 miles on it. I checked the rear end yesterday and it was 1 1/2 quarts low on lube. Filled it up with Mobil 1.

....WOW! Look at all this advice to spend $! Do people like to play with their toys, or what? Your statement seems to say your rear end is getting hot because the paint is pealing off. Have you put a hand on it yet? If it really is smolder THEN look into changing fluid.

Once you drain the rear end (differential - 3.73), how many quarts does it take to fill it back up. I'm going to do mine tomorrow.

Once you drain the rear end (differential - 3.73), how many quarts does it take to fill it back up. I'm going to do mine tomorrow.




Mine took a little less than 4 quarts. I used Mobil 1 synthetic.

Mine was 2 quarts low from the factory...After my first long trip I noticed the oil was low and black...I had it changed with synthetic, it took 4 quarts to fill it up.

Thanks! I'm putting in Amsoil 75W-90 Severe Gear Oil tomorrow.

I beleive the factory puts some sort of break in fluid into the rear. Sometimes they don't seem to fill it up all the way for whatever reason. I pulled mine out at 500 miles and it was black. I refiled it with the GM grape juice and changed again at 20K miles and it was as good looking as the day I put it in. I do not tow. Slows me down:D

Mine was also 1 and a half qts low from factory. Drained it and filled with 4 qts Mobil 1 @ 1000 miles. Guess i better do the front diff too, it was and is full but want no trouble. 10000 miles now.

Our 05 1 ton was one quart low but the dealer checked it before we drove from the lot and we were told it was full. 4 qts of mobile 1 filled it. chevman

I changed the fluid in one of my trucks at 5K and it was as clean as when they put it in. So, to me it was a complete waste of time and money. My brother's truck has the paint coming off of his diff cover as well, and he hasn't had any issues so far. 60K.
I think these trucks have Mobil 1 syn in them from the factory. Should be good to go for a whole lot longer than 500 miles. Just top off and go.

In my truck the rear was low and the front was low and yellow. For the less than $50 it cost me to do it that was cheap insurance and a d@mn good thing I did it.

hrm, i have never checked or changed mine, 29k miles so far

I changed the fluid in one of my trucks at 5K and it was as clean as when they put it in. So, to me it was a complete waste of time and money. My brother's truck has the paint coming off of his diff cover as well, and he hasn't had any issues so far. 60K.
I think these trucks have Mobil 1 syn in them from the factory. Should be good to go for a whole lot longer than 500 miles. Just top off and go.
They have GM grape juice as we call it. It is made by Texaco I beleive. There was a thread about a year and a half ago on this. It is not Mobile 1.

I really doubt the paint "burned" off--I'm betting it's peeling from salt and sand and generally crappy GM paint on rear differential housings.

However, I'm not saying you shouldn't change that fluid! Make sure you use a GL-5 lube, preferably synthetic, in the 75-90 grade. Some guys use 75-140 but unless you're pulling nearly all the time and in hot weather, I'd use the 75-90.

....WOW! Look at all this advice to spend $! Do people like to play with their toys, or what? Your statement seems to say your rear end is getting hot because the paint is pealing off. Have you put a hand on it yet? If it really is smolder THEN look into changing fluid.

I think if you bothered to read "all" the posts you would see that the majority of owners found that their diffs were 1 to 2 quarts low from the factory. Which means they needed to add that much. You might as well drain it at that point and fill it back up with 4 quarts. Makes sense to just about everybody else.

Keep in mind that the spec does NOT have you filling to the rim.


FWIW I filled mine to the rim when I changed it. Mine was not low, but my dealer actually DOES the vehicle prep/inspection along with filling the fuel tank. :cool2:

Be aware ALL fluids are low. Transfer case, front hub, and rear end. GM is saving MILLIONS by not filling these trucks up with fluids.

I have a rear diff. guage on my 04. I have never seen it above 170 deg. pulling heavy.

i gusee i can go look up what it takes but was wondering what i should put in there. i see some are using mobol 1 and some amsoil. thanks for everyone getting back .

Meterman, Mobil 1, Royal Purple, etc, any Synthetic 75W-90 GL-5 Gear Oil.

I think the instruction to fill 1/2 to 1 inch or whatever below the fill plug has got to be a either a cost saving or fuel mileage thing with GM. I am very suspicious of all the Mfgs motives now with regards to CAFE. The old standard has always been to the bottom of the fill plug, or in other words, til it runs out when your filling. I guess there could be some foaming issues with some oils, but doubt any of these good synthetics would foam.

And I totally agree that the paint is being burned off. Have seen many rear axles that have the rust line at and below the exact fluid level. The paint above the line looked fine.

I used valvoline 75W90 synthetic in front and rear. As said 4 qts. in rear, 2 qts. up front.

Is this some way for GM to save more money on the trucks??? Something to consider asking them about!!!

Mine low too. Front only 1/2 qt. rear 1 1/2 qt.

Mine low too. Front only 1/2 qt. rear 1 1/2 qt.

but transfer case is full! :)

I stoped at the dealer last week to get oil and gasket to change.
I had the same problem paint coming off looked like it could have been getting hot. I asked the dealer about it when i was there and they pulled it in for waranty. I figured free oil change cool, nop, broken gov lock and carrier swap. The truck has 11,000 mi.

AAM built the rear differential. It is their recommendation to change the oil after the first tow like John mentioned. Their reason was because this differential was built with tight tolerances and generated a lot of heat during break in. This is why it came with a special high temp oil. My 02 was only a 1/2 quart low but all the newer models I changed oil in were at least one quart low. The black goo is clutch dust. Eaton, the maker of the locker, says it won't cause any problems. I changed mine the first time at 2700. At 31K it looked like new. Eaton said Mobil 1 is acceptable but might cause a little clutch chatter which will do no harm. I filled mine and several for friends. All are running fine. Later! Frank

Is anyone putting an aftermarket Diff. cover on. . . I lost the paint on the first tow. Need to replace the fluid. I'm guessing there is a drain plug on there? Don't have to pull the cover?

I've heard some of the aftermarket ones have a larger oil capacity?

Hmmmmm

Mag-Hytec cover and 8 qts of oil. My rear end is down right cool.

my diff runs 250* when towing heavy in the summer.:weld:

My Express was low as well.