synthetic oil

**diesel-dog** · 04-22-2002, 19:30

Bought my first diesel 2500HD last year and am thinking of using synthetic oil in the front axle and transfer case. According to the dealer the rear differential comes factory equipted with synthetic oil. I have about 7500 miles on it now with 100 miles under load (4 wheel). Any suggestions on type and grade of oil to use.

**Lone Eagle** · 04-22-2002, 20:16

I have run Mobile 1 front to rear in my last three trucks with good success. I have Amsoil in the engine on this one. Later! Lone Eagle

**csimo** · 04-22-2002, 20:32

I'm running Mobil 1 synthetic in the rear and Redline synthetic in the front. Any high quality GL-5 synthetic gear lube will work fine.

Don't use Mobil 1 motor oil. It's not rated CH-4. Use Delvac 1 instead if you like Mobil products.

[ 04-22-2002: Message edited by: csimo ]</p>

**Alli-max** · 04-23-2002, 10:44

how many qts are in the front end??

LanduytG · 04-23-2002, 11:11

Alli-max
You will need 2 quart.
Greg

**Alli-max** · 04-23-2002, 13:13

Gracias Gregory!

**cmadmaxman** · 04-23-2002, 20:25

I'm getting ready to change all the oils front to back before heading out to BC. I have not seen what is required in the transfer case for the 4x4. Is it Dextron III?? How much??
Thanks guys for the help.

**srubrn** · 04-23-2002, 21:21

cmadmaxman ,

I think the product in the transfer case is called transblend and is only aavilable at GM dealer. If I am not mistaken your owners manual says on most lubes use GM or equivalent, but not for this lube, so I guess you better go with GM. Check your manual, I would look for you but I am too lazy to get up and go get mine.

**cmadmaxman** · 04-24-2002, 00:34

Thanks srubrn.
Now that I think about it, I remember something like that. The problem was that it was talking about the HD with the 6.0 gaser transfer. Not the one attached to the allison. With the allison transfer case we don't have auto track like I had with the 6.0 gaser that I had in the 2500. Will do some more checking and look into the owners man. deeper. Any more ideas??

**DmaxMaverick** · 04-24-2002, 03:33

cmadmaxman is right. The transfer case in the HD's requires Dexron III (dino or synthetic). It is not an Autotrac transfer case, which requires Autotrac II fluid. The Autotrac is the transfer case on vehicles equipped with Autotrac (as an option, not all of them), like a 2500 (not HD), 1500, Tahoe, Yukon, etc. Push button 4X4 does not mean that you have Autotrac. It is the same as a manual shifter, only it is shifted electrically.

Autotrac II fluid contains friction modifiers that can be damaging to boxes that are not designed for them.

**TraceF** · 03-10-2003, 00:36

My options list says I have Autotrac Active Transfer Case. How do I confirm this?

The option code is NP1 (Electronic shift transfer case). Is this a contradiction?

**mike.morris** · 03-10-2003, 06:56

TraceF,

Check this link out from the January GM Techline:
http://service.gm.com/gmtechlink/ima.../TLJan03e.html

Looks like the only 2 options for the HD trucks are the NP1 and NP2 transfer cases. The NP1 is the pushbutton version while the NP2 is the manual version. I have the NP1 in my '03, and the service manual states that Dextron III ATF is the correct fluid.

FYI, the autotrac transfer case is RPO code NP8. I had this in my '99 gasser. This transfer case takes the Autotrac II fluid sold at the GM dealer. There are several other listed, but this should clear up your, and anyone elses confusion.

Mike

**TraceF** · 03-10-2003, 09:32

Thank you Mike.

**BobW** · 03-11-2003, 00:38

Any thoughts on using Allison's Transynd in the transfer case?

**Toddster** · 03-11-2003, 14:32

Thats even better yet....

**Diverguy** · 03-11-2003, 16:57

Diesel-dog;
I use Petro-Can Syngear 75W-90 in the front and rear axles plus Shell Donax TG (Dexron III ATF)in the transfer case.

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