Front and Rear Diff Fluid

local392-496 · May 27, 2006

I haven't had a chance to get a manual on my truck yet. I was hoping to change the diff fluid on my truck this weekend. Anyone know what the spec is for fluid and capacity on a 2003 2500HD 4x4 w/locker. Also the transfer case to. It would be a great help. Thanks.

4x4in · May 27, 2006

I haven't had a chance to get a manual on my truck yet. I was hoping to change the diff fluid on my truck this weekend. Anyone know what the spec is for fluid and capacity on a 2003 2500HD 4x4 w/locker. Also the transfer case to. It would be a great help. Thanks.

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I just changed mine on my 02 2500HD with locker. I can tell you it is A LOT. I don't know for sure because I was filling my quart containers from a 5gal bucket of Conoco Synthethic. I think it was around 4qts. Don't forget to add the locker additive. I have heard you don't need it if you run synthethic fluid but the dealer says you do and for about $4 I will run it. One bottle will be sufficient for the rear end. With the spare tire in the way it is kinda difficult to fill. Don't forget the differential gasket is dealer only also. It is $10

As for the t-case fluid the G.M. blue synthetic fluid I understand is best and that is what I run. This too is a dealer only item. The t-case takes just under 2qts. I bought the t-case fluid and the rear end additive from the dealer for just under $17.

I run synthetic in my front end also.

snoman · May 28, 2006

Strange, I have been plowing snow for over 20 years with new and old trucks and I have always used good old Dino oil and I have never had a axle/differentail problem once and I work those axle hard sometimes too. Before that I hauled very heavy 20k plus) farm grain trailers on dino oil too with not axle problems. Same with Tcase, Dino oil too and never had any problems there either in well over 30 years of 4 wheeling. Regular maintainance is the key here not the need for it to be SYN because it still needs to be changed too as it also gets dirty with time.

dewfpo · May 28, 2006

The rear diff comes from the factory with synthetic fluid. It seems most folks here do not add the additive to the syntheic fluid. The rear banjo takes between 3.7 - 4 qts. The transfer case 2 qts. Dex3 or synthetic. Your choice. Front pumpkin take 2 quarts. No need for synthetic there but for only 2 quarts, why not.

DEWFPO

snoman · May 28, 2006

The rear diff comes from the factory with synthetic fluid. It seems most folks here do not add the additive to the syntheic fluid. The rear banjo takes between 3.7 - 4 qts. The transfer case 2 qts. Dex3 or synthetic. Your choice. Front pumpkin take 2 quarts. No need for synthetic there but for only 2 quarts, why not.

DEWFPO

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Your nickle and if you want to pay more for it have at it but it will not last any longer than it will with Dino oil "IF" you properly service it.

local392-496 · May 28, 2006

Thanks for the info, but what about what weight gear oil for the diffs?

snoman · May 28, 2006

Thanks for the info, but what about what weight gear oil for the diffs?

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You can use 75w90 in rear but in front you should use 80w90 unless it is extremely cold. The reason for the 80w90 in front is that the front spider gears spin off in 2wd (one axle is disconnected and the other spins off in spiders and they want a minimum film strength and thickness there to protect them.

MS3DALE · May 28, 2006

You DO NOT need the additive in these trucks,It is not recommended or required by GM.

It dosen't matter if you run dino or synthetic gear lube either,The additive is not needed or required.

I've seen more than a few rear-ends ruined by guys adding the additive when its not required.

4x4in · May 28, 2006

Thanks for the info, but what about what weight gear oil for the diffs?

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You can use 75w90 in rear but in front you should use 80w90 unless it is extremely cold.

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This is one of the primary reasons I run synthetic. For the days that get -20 & -30 degrees I don't have to worry about my fluid being thick.

As far as the additive, If I do have an eventual problem (hopefully within warrenty) I feel it will be warranty since it was recommended to be put in by the dealer.

I will continue to run the synthetic because that is what gives me the warm and fuzzy feeling. My whole truck has sythetic and I like it. Just my .02

snoman · May 28, 2006

This is one of the primary reasons I run synthetic. For the days that get -20 & -30 degrees I don't have to worry about my fluid being thick.

No real need for it up front as it is quickly warmed up by motion and engine on a IFS truck. (it is noit like a diff hanging down with live axles that does not really warm up in cold weather) I have plowed snow at 40 below zero with dino oil and never had any axle failures of any kind. Axle that do fail it is from lack of service or wrong oil typ, not because it is not SYN in nature. Because of the way the spider gear spin out in that axle, you really do not want lube to be too thin at times.