I have approx 600 miles on my truck now,will be towing my fiver approx 1000 miles here in a few weeks. Manual states change the fluid at 500,do i need to stop and do this or wait till i get to my sunny destination. Where can i get it changed other than the dealer and what fluid do i use? Thanks in advance

Coach,


I would wait until you get back from your trip. The recommendation is to change it after at least 500 miles of towing. As to fluid, a good synthetic 75-90 Gear Oil is what you want. AV Lubricants carries Mobil-1, my local Wal-Mart carried a Penzoil synthetic 75-90, which is what I went with. For very hot/heavy towing GM recommends a different weight oil, but I can't remember the weight. I am sure someone here will chime in soon.


It is easy to change, as there is a drain plug at the bottom of the differential, and an easy to reach fill plug at the top. Quantity, I believe, is about 3.5-4.0 quarts, but I may be mistaken on that. When I changed mine I also put a Mag-Hytec differential cover on. Gives 8 quart capacity to the diff, a magnetic dip-stick for collecting metal shavings, and then there is the cool factor, which can never be taken lightly!http://www.dieselplace.com/forum/smileys/Big Smile.gif


Hope this helps.


John

For heavy towing I believe the recommended gear oil is 75w-140.


Joe

Ditto on the 75w-140, if you have a 4x4 and do the front diff, make sure you get the white cap from the dealer if you use synthetic lube. I was surprized at the amount of crud that came out of mine after just one winter, wish I had odne it sooner.


Mark

Coach, notice your from MI, what part? I might of asked you already, sorry if I did. Anywho, you can change fluid yourself, drain pan and some parts from your local experthttp://www.dieselplace.com/forum/smileys/Cool.gif and your on your way


Eric

dmaxalliTech


I went to the local Chevy dealer and the parts guy had never heard of the white differential cap for my 4X4 http://www.dieselplace.com/forum/smileys/Cry.gif. I would like to switch to a synthetic 75W90 for the front. Do you have a part number for the cap?


Also, gmparts.com has the 75W90 for half the cost my local dealer charges.


Thanks.

John, part no for vent is 12479296. I offer the lube and cap for 130.00 shipped ( 6 qts of grape juice)


Eric

Can't beat that. I want to do the front and rear so do you think a total of 10 quarts?

Fish2Max. 6 Qts is all you need for the front and rear. 4 qts in the rear and 2 qts in the front. Dmaxallitech price is a real good one. My dealer wants $30.00 a qt for the grape juice alone.

I used Mobile 1 synthetic at $6.99 a qt. at Advance Auto Parts.

Mobile 1 for me also. Its great lube, and much cheaper than the grape juice. I know, I know.....its not GM specific..http://www.dieselplace.com/forum/smileys/Ermm.gif....I don't care either. Its quality, GL-5 rated gear oil, and will work just fine, IMO. http://www.dieselplace.com/forum/smileys/Approve.gif

I used Valvoline Synthetic GL5 rated diff. fluid.


I have The G80 locker and have had no problems to date.


Thttp://www.dieselplace.com/forum/smileys/Clown.gifNY

I used Valvoline Synthetic GL5 rated diff. fluid.


I have The G80 locker and have had no problems to date.


Thttp://www.dieselplace.com/forum/smileys/Clown.gifNY


Do you also need any of the GM Friction Modifier?
(I don't have a Helms for my '04 yet)

Thanks!

T.

The G80 does not require a friction modifier.


Mark

What is the differential cap you guys are talkin about ???? for the front or the autotrac 4x4 ? Also my rear end does not have a drain plug http://www.dieselplace.com/forum/smileys/Embarrased.gif I did change the fluids in the auto trac at 50k as well as the front diff. I need to change the rear fluid as I have just topped it off to this point. 56k. What kind of form a gasket is best used to re seal. I spend to much time in the woods so I have stayed away from the aluminum rear end covers. I have a 02 and it seems my manual is missing a few points like changeing the Allison spin on filter at 7500 miles http://www.dieselplace.com/forum/smileys/Angry.gif I did it at 50k and changed 8qts (pan drain). The filter had boo coo metal shaveings. I dented the filter at 55k so I did the same thing again and it had metal shaveings it still http://www.dieselplace.com/forum/smileys/Angry.gif NAPA has the spin on filters for $18. Has anyone changed the inside tranny filter ??? I see on the Allison site they only recommend changeing it at overhaul.

I used Redline Synthetics from front to rear.75w-90 gear lube(4 rear, scoosh over 2 front.) 15W-40motor oil. Changed diffs at 750 miles and then again at 20K and then at 50K. No additives required. Works perfect. $6.95 a qt.http://www.dieselplace.com/forum/smileys/Clap.gif


Edited by: Duramax Dually

BlueMaxxxx,


The HDs don't come with the AutoTrak. Do you have a half ton?http://www.dieselplace.com/forum/smileys/Confused.gif


There is a black vent cap on the top of the front diff that is incompatable with synthetics. If you run synthetic in the front, you need to change to the white cap Eric mentioned about. One thing I have noticed is that ALL of the synthetic gear lubes stink. http://www.dieselplace.com/forum/smileys/Throw Up.gif Redline, Grapejuice, Amsoil, it doesn't seem to matter who's. Maybe it's the additives to make them GL5?

I have a 2500 HD ext cab SWB. I guess I gotta remove the skid plate and take another look at the front diff. When I drained it I just used the recommended conventional gear lube. The 4x4 unit which I though was a autotrac, maybee I'm confused though. It took a special blue fluid. GM part # 12378508 $6.96 qt. Do you have the shift on the fly ? Dave

BlueMaxxxx,


The rear diff has a drain plug on the very bottom of the diff itself. Not on the pan. It should take a 3/8 ratchet drive. The plug on the pan is for checking the fluid level, and re-filling. Should tale 4 quarts.


Its obvious by your posts you have an auto transfer case. As chuntag95 stated, the HD's do not come with the "autotrak". They are two different animals. Your 4X4 buttons should have 2Hi, 4Hi, and 4Lo. Right ? Not a button that says "Auto". I am not sure if the auto transfer case takes a special fluid or not. The manual case just takes Dex III.

I have a 2500 HD ext cab SWB. I guess I gotta remove the skid plate and take another look at the front diff. When I drained it I just used the recommended conventional gear lube. The 4x4 unit which I though was a autotrac, maybee I'm confused though. It took a special blue fluid. GM part # 12378508 $6.96 qt. Do you have the shift on the fly ? Dave


There is a pushbutton transfercase that will shift on the fly, but is NOT the auto track. It uses standard Dexron III transmission fluid. The differential uses 80-90W Gear lube, but most go with the 75-90W or the 75-140 depending on location, towing, etc. As I recall, the manual is confusing about who has the autotrac, but it is not offered in the 3/4 and 1 ton units.

Ok I do have the auto transfer case but Not the autotrak. The Manual still says use Auto-Trak 2 fluid which is the part # I listed above. Which was a pain to re-fill. I appreciate the tip on finding the drain plug on the rear end. That will make changeing the fluid a whole lot easier. My manual also says 80w-90 in the front axle and 75w-90 synthetic in the rear. Thats what I have used so far but I need to drain and re-fill the rear axle again and take a look at the cap on the front diff.

I have a 2500 HD ext cab SWB. I guess I gotta remove the skid plate and take another look at the front diff. When I drained it I just used the recommended conventional gear lube. The 4x4 unit which I though was a autotrac, maybee I'm confused though. It took a special blue fluid. GM part # 12378508 $6.96 qt. Do you have the shift on the fly ? Dave


There is a pushbutton transfercase that will shift on the fly, but is NOT the auto track. It uses standard Dexron III transmission fluid. The FRONT differential uses 80-90W Gear lube, but most go with the 75-90W or the 75-140 depending on location, towing, etc. As I recall, the manual is confusing about who has the autotrac, but it is not offered in the 3/4 and 1 ton units.





Oops. Left out an important word. http://www.dieselplace.com/forum/smileys/Embarrased.gif

My manual says to put Autotrac fluid in the transfer case not ATF fluid. It does say use the ATF in the manual transfer case. Dave

Speaking of stinky rear end fluid, has anyone ever smelled any oil that smells good? It all stinks to me.http://www.dieselplace.com/forum/smileys/Confused.gif

BlueMaxxxx, there is only one type of transfer case in out truck. It is considered a manual by GM because you either shift a handle or push a button. Either will shift on the fly. It uses Dexron III fluid. Later! Frank

OK, I am even confused now!!


Lets see if I can help confuse things further.


Front Diff-- OEM fluid is 80-90 gearlube. It is acceptable to replace it with 75-90 synthetic fluid. Any quality fluid is acceptable as long as it meets GL-5 requirements. When going to any type of synthetic fluid, its advisable to change the vent cap on the front diff to the "white" cap. This cap is the replacement cap and the black cap is no longer offered. Part No. 12479296 for the cap. The refill capacity for the front diff is 2 quarts.


Transfer Case- First, lets discuss the options for the transfer case. If you are driving a 2500 HD or 3500 pickup, you have a NV-263 case(push button shift) or a NV-261 case ( floor manual shift) There is no automatic transfer case in these trucks. The 1/2 trucks and I believe the 2500 (non-HD) trucks will use the NV-241 (floor manual shift), the NV-243 ( push button shift) or the NV-246 case ( auto-trak, push button ) We will concentrate on the 2500HD and 3500 trucks here. The OEM fluid for these is Dex III or equiv. This means that any quality Dex III fluid or synthetic will work. There is no changes necessary to switch to synthetic. Capacity is 2 quarts.


Rear diff- The 2500HD and 3500 trucks use an American Axle 11.5" rear end. Its available with the Eaton limited slip option (G80). The Diesel engine equiped trucks only come with a 3.73 gear. The 8.1 trucks have either a 3.73 or a 4.10 option. The OEM fluid is 75-90 synthetic lube, commonly referred to as "grape juice" for its smell. A synthtetic lube must be used in the rear axle and it must meet GL-5 requirements. I dont know the additive package of the aftermarket lubes but I would think that the quality lubes contain the necessary additives for the limited slip. It is not necessary to add any additive to the rear end when servicing. Capacity is 4 quarts. It is recommended by Eaton to service the rear axle after the first 500 miles of towing or 5000 miles of driving.


I hope this helps out a littlehttp://www.dieselplace.com/forum/smileys/Cool.gif


Eric

Arggghhhh !http://www.dieselplace.com/forum/smileys/Confused.gif My manual lists the two different fluids. Are they useing the same manual for the 1500 ???? So Do I need to drain out the GM part # I listed above which is the blue autotrac fluid and re-install ATF. If so I will definately use a synthetic. Man its a PITA getting the fluid back in that thing. Dave

Well I decided to go ahead and get the '04. The 04 Duramax manual has Vin id info and engine compartment schematics for both the LB7 and the RPO LLY. The bad news is that at 200 miles its pukeing tranny fluid all over the place http://www.dieselplace.com/forum/smileys/Dead.gif http://www.dieselplace.com/forum/smileys/Angry.gif So back to the dealer tomorrow. http://www.dieselplace.com/forum/smileys/Cry.gif