Rear end fluid

[Tim Richardson]

I am approaching 500 miles on my new truck, so I am about the change the rear end fluid. After doing numerous searches on this subject, I only seem to have more questions. :rolleyes:

1. How do I know if I have a G80 Eaton Rear end? If I don't have this one, then what do I have? Also, does this make a difference on when I change fluids?

2. If I decide to go with the GM grape stuff, is there a cheaper place to buy it then at the dealership for $28 a quart?

Also, I have a picture of my window sticker on the web site in my signature line.

Thanks

Tim

[sonofagun]

Tim,

Your invoice says locking differential. So you have the Eaton. E mail Dmaxallitech (mailto:tqauto@aol.com) for the grape juice. GM part no for the 75w90 is 12378261 and for the 75w140 is 12346140. Based on your previous post I would go withe the 75w90. Gmparts direct has it to for around $16 but their shipping is high. www.gmpartsdirect.com (http://www.gmpartsdirect.com)

Regards,
Bob

[Joe.G]

Try the Amsoil Series 2000 75-90, have used it for about 95000 miles now with no problems, I have a 2001 All/Dmax equiped with the same rearend that you have. I think it retails for $9.20 US, it will take about 4 quarts if I remember correctly. You should be able to find a dealer up there easily.

[Idle_Chatter]

Tim, there's a white lable on the inside of your glovebox door that contains your vehicle's options list. If you find G80 on that list, you have the G80 option, which is the Eaton locker diff. I agree with Joe. The GM "grape juice" is very pricey. Many members have used Mobil-1 synthetic gear lube (about $7 a quart) or Redline or Amsoil, which I'm using in both diffs. Whether you have the locker or not, there's no difference in lubes as the Eaton does not require any friction modifiers. Non-lockers will probably require more lube due to more space taken up in the punkin by the Eaton.

[battmain]

You can also call your local parts dealer and see if they will match the mail order price of around $19 when I was looking. They did, but when I went, they raised the price by a dollar. I grumpily agreed since it would work out the same with shipping from mail order.

[TraceF]

Does the grape juice have a spec that any other full synthetic 75w90 can't meet? I am using Pennzoil. It's about $13 per GALLON at the local Pennzoil distribution center. I have a 5 gallon bucket of it and bought a $25 pump that makes the fluid easier to deal with.

[Tim Richardson]

I have decided to go with the mobil synthetic. If I buy the quart containers, is there any reason to buy a pump to put it in, or does it go in fairly easy straight from the container?

Thanks

Tim

[bigRazor432]

No reason to buy a pump. I just changed mine this weekend and used the quart containers.

bigRazor

[jbplock]

Tim,

As bigRazor said a pump is not needed. There is enough head room to poor the fluid from 1 quart bottles. I also used Mobil-1 75w90 and found that if you poke a hole in the bottom of the bottle it helps the fluid flow faster. smile.gif

[roegs]

TraceF..first of all, its good to see you back again! As for the GM grape lube, GM lists specfication 9986115. Dunno what the spec is, but when I called a number of mfgs (Mobil, Texaco, Shell, Amzoil, etc), they could not confirm that their product met that specification.

[Gasman1075]

What is the capacity of a none locker type 2003 HD rear end? My dealer said that 3 qts would do it but it seems about 1 inch low and I don't want to pull hard if it is low.

Walt

[AbqGeorge]

Gasman,

With locker, mine took exactly 4 quarts. Since the locker mechanism takes up some of the room, my guess would be a bit over 4??? One inch low is, ah, one inch too low.

Geo.

[Tim Richardson]

I have noticed from some of the posts that say capacity is ABOUT 4 qts. Has anyone put in more than 4? The reason I ask this, is because I would like to know whether or not to buy 4 or 5 qts before I drain.

Thanks

Tim

[JimWilson]

It's something like 3.8, so 4 should be fine.

[foots]

Since when do you change differential oil at 500 miles ???

[jbplock]

Originally posted by foots:
Since when do you change differential oil at 500 miles ??? Johnny,
IIRC, the 500 mile change was recommended by Eaton for a G80 locker after 500 miles of towing on a new diff. This topic has been dicussed in great detail in the past. Try seaching the forum for more info. smile.gif