My rear end

[ChopperBill]

Went to the dealer this morning to get a price on a complete service. Engine oil, filter, trans filter and change rear diff oil. They told me because of the the new synthetic oils in the rear end it didnt need service until 100,000 miles. I said I thought it should be changed at 6,000 miles or so. He said in the past with dino oils it would be. They want over $100 to change the diff oil! Well I have the 100,000 5 year drive train warranty and figured I would just let them worry about any problems till then. What do you guys think?

[wild bore]

Chopper,I spent about 40 bucks on oil when I changed mine, I also got a little hand pump that screws into the 1 qt. jugs,alot of pumping though. It sounds about right if the dealer charges 60.00 an hour for labor.

[Trucker Tex]

Interesting topic title, Chopper. I didn't quite know what to expect when I clicked on this one.

BTW, conventional wisdom is that you should change rear end differential fluid after 500 to 1000 miles to flush out manufacturing contaminants and shavings that occur from newly cut gears wearing in. After that, you should be good to go for a while.

Who knows, but it can't hurt and its relatively cheap insurance.

TT

[ChopperBill]

Tex, thats what I kind of thought but the service rep at the dealer kind of insited on 100,000 miles. They are the ones that have to do any warranty so I kind of thought they would like to see it changed sooner. Will end up doing it my self when it warms up some. Cant see me paying someone $100 to lube my rear end. smile.gif

[ 02-02-2003: Message edited by: ChopperBill ]</p>

[JimWilson]

Oh, I gotta respond to a thread with a title like this! :D :D

The rear end oil should be replaced by 3K, whether or not you tow. And that hold especially true if you have the G80 option (Eaton locker).

I used AMSOIL in mine, and it took about 2.8 quarts. IIRC it was about 6 bucks a quart, so it costs less then $20 for the oil. I have a funnel with a 2 foot flexible hose, so when I was adding the new fluid I sat on a small chair right next to my PS rear tire, snaked the funnels hose into the fill plug on the diff and started pouring.

All told, it took me about 3/4 of an hour to do, and that includes the 1/2 hour I let it drain. It's really not that hard, and definitely worth the effort if you want to try it yourself. A well lubed rear end is a good thing! :eek: tongue.gif

[MaxACL]

There's a lot to be said here but I'll butt out.

BTW if you put the quart bottles in hot water for a while, it'll flow much better through the funnel.

[IndigoDually]

I have been very hesitant to even open this thread. :D I changed my fluid after towing at around 1000 miles. I checked it at 500 and it was clean. After towing some I changed it and it was black from the G80's friction material. I again changed it around 10,000 and it was pretty black again.

John

[technician]

ChopperBill,

Did not change my diff oil in my 02 3500 as per manual ( nothing about G-80 break in ) @ about 22,500 the rear started clunking and poping. I had dealer service it in case of warranty issues. Dealer stated that rear should be changed @1000mi. for break in, then @100,000mi. cost me $127.00 all total. No more noise..... I'm doing it again @ 25,000 and changing to Mobil.

[dave p]

did you remove the allen at the bottom to drain the dif? it sure makes it easy, mine took a little over 4 qts. i filled it till it ran out and replaced the plug, after it quit running out. i used mobil synthetic. dave p :cool:

[JimWilson]

When draining you should take out both plugs, the fill and the drain. That's what worked best for me.

Both the dmax and 8.1 take about 4 quarts, while the 6.0 only takes about 3. That's why mine took less then yours, because I have the smaller engine.

[ChopperBill]

Is "Mobil 1 Synthetic Gear Lube" the recommended lube? Would be easier for me to obtain than Amsoil.

[jbplock]

Mobil 1 75w90 GL5 meets the requirements for our Diffs.

The following was previously posted by TxDoc. (see http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=7&t=000607&p=)


Here is some info Eaton sent me in the past:
"GM introduced the new body style in 1998. At the same time they upgraded
the differential and changed to a synthetic lube. The G80 is specifically
designed to give ultimate performance with this lube, and the lube contains
special additives that help reduce slip stick that occurs between the
clutches. the GM synthetic lube typically runs about 100+ degrees cooler
than mineral base lube, which is better if you do allot of towing or heavy
hauling. I would recommend that you stay with the GM synthetic, not Mobil 1.
If you don't tow or haul you could use the pre 1998 mineral lube without
degrading performance of the differential. this would be a cheaper option
but require more lube changes. "
"Axle tolerances of the 1/2 ton trucks are very tight. The recommended
procedure was to change lube after 500 miles of heavy towing, which would is
considered a break in period. This breaking period generates high heat
conditions in the axle which was found to degrade the synthetic beyond the
point of mineral lube. After the 500 mile lube change, the axle is broke
in and does not generate the high heat. If you use GM synthetic after the
break-in period, it can be considered "lube for life", although some say to
change it at 40,000 - 50,000 mile intervals."

"If you don't tow, don't worry about the oil change as it a waste of money."


"If your truck is pre 1998 or the old style, it comes with mineral lube. IN
that case you need to stay with mineral because the seals are designed to
work with it. If you changed from mineral to synthetic you'll cause your
seals to swell and eventually leak. It's ok to go from synthetic to
mineral because you won't cause swelling. many of your stop leak
chemicals effect seals in this manner, resulting in a short term fix but a
long term problem."

Back in November, I received the following:
"From Mr. Ralph Holmquist of Eaton, the maker of the locking differential:
"The maintenance schedule for the rear axle was developed by American Axle &
Manufacturing and GM truck based on multiple tests. The Eaton locker does
not require additional maintenance nor does it add heat to the lube. The
lube will darken due to the carbon wear on the clutch surfaces, much the
same as a disc brake pad & rotor. This does not damage axle components such
as seals or bearings. However, a new axle can produce excessive
temperatures (plus 350 degrees F) due to the ring & pinion breaking in that
will break the lube additives down. Avoid high loads, trailer towing and
high speed extended driving during the initial break in of the vehicle.
After the break in period axle temps will level at a much lower figure.
Lube changes are a good idea because the additives are replenished and
contaminates such as casting sand are eliminated. The axle is filled at the
factory with a synthetic 75w90 GL5 rating made by Texaco under part # 2276.
The GM service # is 12378261. This is the only lube we have done extensive
testing with to insure locker compatibility. The only negative to using one
of these other lubes is an increased potential for clutch chatter. This
really doesn't hurt anything and can be corrected by changing the lube. I
noticed in the latest GM owners manual the term "or equivalent" when
referring to the lube specification. Look for a GL5 rating on the bottle to
make sure the ring & pinion, seals & bearings are protected. Limited slip
additive is not needed."
The following information outlines the type of
rear axle lubrication utilized in GM Truck axles.
I. Fluid Type
II. The 1500, 2500 and 3500 GMT 800 Trucks utilize SAE 75W-90 Synthetic Axle Lubricant. The GM part number is 12378261 and the specification is 9986115.