Maintenance Advice/Help

[mcmonroe]

To All,

I have a few maintenance questions I would like to run by you guys. I realize that this is old hat for most of you

[Idle_Chatter]

1)The capacity section does not list a quantity of fluid needed for the rear axle. Could someone give me a idea of how much fluid it holds?

The rear axle capacity is listed as 3.78 qts - which is supposed to be about 1/2" below the fill hole. 4 qts will pretty much bring it up to the bottom of the fill hole and will do no harm and who wants .28 qts of left over fluid?

2)The manual lists the fluid as 75W-90 Synthetic with GM part number 12378261. There is no mention of a friction modifier additive. I know that with Corvettes and other vehicles that a friction modifier additive is require. Is this not necessary on the 2500HD trucks? If it is required what is the part number?

No modifier required for the Eaton G-80 locker. GM specifies the "grape juice" synthetic, Dealers sell it at an exorbinent price (something like $28/qt). Many folks have gone to a good synthetic alternative - Redline, Mobil 1, Amsoil, etc.

Allison Transmission

1)If changing the fluid in the Allison transmission by removing the pans drain plug and also replacing the spin on filter

[mcmonroe]

Thanks for the very detailed post Tom. I really appreciate it.

One more question.. (smile)

Front Axle

The manual specifies a 80w-90 gear oil with GM part number 1052271. I would assume that this is a non-synthetic gear oil.

What are folks using when switching the front axle to a synththic fluid? Will the 75w-90 rear lube with GM part number 12378261 work? Is there a better alternate that is actually 80w-90?

There must be some reason they specify an 80w-90 fluid for the front versus the 75w-90 for the rear.

Many thanks again,

Mark Monroe
Harrisburg NC
2004 K2500HD D/A Crew Cab

[Idle_Chatter]

I think the difference is just as you supposed - synthetic vs. dino. I'm using Amsoil 2000 75W90 synthetic in both in my truck.

[More Power]

Good response Tom,

GM issued a notice to all its dealers a while back to install (at no charge) synthetic lube in the front diff. Seems those owners living in very cold climates experienced seal leakage with the dino fluid. If you live in a warm climate, it's not an issue and isn't necessary. I haven't heard any reports from owners who requested and didn't receive the syn lube. I still have the dino fluid in mine.

I suspect all trucks produced since the notice got syn lube at the factory.

MP