Transfer case and Diffs
- Thread starter Just1More
- Start date
- Status
What is the factory recommendation for the TC?
If it's an ATF, then I would use Mobil 1 ATF, or an AMsoil ATF.
If it's an ATF, then I would use Mobil 1 ATF, or an AMsoil ATF.
If you have an "auto 4wd" button on your tcase you need the GM autotrak II tcase fluid. If you only have the 4lo, 4hi and 2hi buttons on your tcase it gets Dexron III. Your diffs get 75w90 synthetic.
Originally Posted By: PT1
If you have an "auto 4wd" button on your tcase you need the GM autotrak II tcase fluid. If you only have the 4lo, 4hi and 2hi buttons on your tcase it gets Dexron III. Your diffs get 75w90 synthetic.
Thats exactly what I have. I was told to make sure to use Synthetic Dex III in the transfer case. Yes for the Syn????
If you have an "auto 4wd" button on your tcase you need the GM autotrak II tcase fluid. If you only have the 4lo, 4hi and 2hi buttons on your tcase it gets Dexron III. Your diffs get 75w90 synthetic.
Thats exactly what I have. I was told to make sure to use Synthetic Dex III in the transfer case. Yes for the Syn????
Originally Posted By: Just1More
Originally Posted By: PT1
If you have an "auto 4wd" button on your tcase you need the GM autotrak II tcase fluid. If you only have the 4lo, 4hi and 2hi buttons on your tcase it gets Dexron III. Your diffs get 75w90 synthetic.
Thats exactly what I have. I was told to make sure to use Synthetic Dex III in the transfer case. Yes for the Syn????
Go to Autozone and get Mobil1 Multivehicle ATF and all is good. It should take about 2 quarts. I think it is an NVG 231 tcase? Anyway, the drain & fill bolts are on the back. On many of them they do not thread in all the way. If they look like they have some threads showing before you remove them, that is normal so do not try to force them in there all the way. I use white loctite (autozone) hydraulic thread sealer on them. Never a leak. Your diffs might require the GM 75w90 grape scented (not kidding) synthetic gear lube. If so you have to get that at the dealer.
Originally Posted By: PT1
If you have an "auto 4wd" button on your tcase you need the GM autotrak II tcase fluid. If you only have the 4lo, 4hi and 2hi buttons on your tcase it gets Dexron III. Your diffs get 75w90 synthetic.
Thats exactly what I have. I was told to make sure to use Synthetic Dex III in the transfer case. Yes for the Syn????
Go to Autozone and get Mobil1 Multivehicle ATF and all is good. It should take about 2 quarts. I think it is an NVG 231 tcase? Anyway, the drain & fill bolts are on the back. On many of them they do not thread in all the way. If they look like they have some threads showing before you remove them, that is normal so do not try to force them in there all the way. I use white loctite (autozone) hydraulic thread sealer on them. Never a leak. Your diffs might require the GM 75w90 grape scented (not kidding) synthetic gear lube. If so you have to get that at the dealer.
If you have a LEVER on the floor, then you use a ATF fluid in the transfer case.
ANYTHING PUSH BUTTON you need the fluid avail ONLY from GM dealerships or online.
On your rear diff, you may need 85-140 gear oil. Check in your manual as it will state what you need.
My truck has the lever and I use Supertech AFT fluid in it. The front diff has Supertech 75w-90 and rear end has Amsoil 75-90 in it. Works like a charm.
Take care, Bill
ANYTHING PUSH BUTTON you need the fluid avail ONLY from GM dealerships or online.
On your rear diff, you may need 85-140 gear oil. Check in your manual as it will state what you need.
My truck has the lever and I use Supertech AFT fluid in it. The front diff has Supertech 75w-90 and rear end has Amsoil 75-90 in it. Works like a charm.
Take care, Bill
The T-case is probably the NP261.
I use Mobil 1 ATF in my Jeeps NP231HD. Works pis-sah.
I use Mobil 1 ATF in my Jeeps NP231HD. Works pis-sah.
Originally Posted By: Bill in Utah
If you have a LEVER on the floor, then you use a ATF fluid in the transfer case.
ANYTHING PUSH BUTTON you need the fluid avail ONLY from GM dealerships or online.
On your rear diff, you may need 85-140 gear oil. Check in your manual as it will state what you need.
My truck has the lever and I use Supertech AFT fluid in it. The front diff has Supertech 75w-90 and rear end has Amsoil 75-90 in it. Works like a charm.
Take care, Bill
INCORRECT!
You have a 2500HD so you do not have an "Automatic" T-case. You have an Electric shift model. Same as the floor shift except done by pushing a button. "Automatic" means the t-case shifts in and out of 4wd as needed.
Yor diffs take 80w-90, UNLESS the rear diff is the Eaton locker. Look for RPO code G80 on the sticker inside the glove box. The G80 uses a synthetic 75w-90 only available through GM (expensive). However, many have used other products without any problems.Also, the manual says a 75w-140 may be used in a truck that sees alot of towing.
FWIW, I have Mobil1 ATF in my t-case and Mobil1 75w-90 LS in both diffs. my Locker works fine.
If you have a LEVER on the floor, then you use a ATF fluid in the transfer case.
ANYTHING PUSH BUTTON you need the fluid avail ONLY from GM dealerships or online.
On your rear diff, you may need 85-140 gear oil. Check in your manual as it will state what you need.
My truck has the lever and I use Supertech AFT fluid in it. The front diff has Supertech 75w-90 and rear end has Amsoil 75-90 in it. Works like a charm.
Take care, Bill
INCORRECT!
You have a 2500HD so you do not have an "Automatic" T-case. You have an Electric shift model. Same as the floor shift except done by pushing a button. "Automatic" means the t-case shifts in and out of 4wd as needed.
Yor diffs take 80w-90, UNLESS the rear diff is the Eaton locker. Look for RPO code G80 on the sticker inside the glove box. The G80 uses a synthetic 75w-90 only available through GM (expensive). However, many have used other products without any problems.Also, the manual says a 75w-140 may be used in a truck that sees alot of towing.
FWIW, I have Mobil1 ATF in my t-case and Mobil1 75w-90 LS in both diffs. my Locker works fine.
Do not some of the 2500HD have the NVG246 in them?
I've seen the ones with AUTO 4WD as the big button and those DO take the special GM only fluid.
He said he has the AUTO 4WD button. How is that NOT the Automatic?
Bill
I've seen the ones with AUTO 4WD as the big button and those DO take the special GM only fluid.
He said he has the AUTO 4WD button. How is that NOT the Automatic?
Bill
Originally Posted By: Just1More
Originally Posted By: PT1
If you have an "auto 4wd" button on your tcase you need the GM autotrak II tcase fluid. If you only have the 4lo, 4hi and 2hi buttons on your tcase it gets Dexron III. Your diffs get 75w90 synthetic.
Thats exactly what I have. I was told to make sure to use Synthetic Dex III in the transfer case. Yes for the Syn????
Based on what the OP highlighted here I would think he only has the three buttons 2hi,4hi and 4lo which is the electrically shifted version of your floor shift Not an "Auto". You stated anything push button gets the Autotrac II fluid and that is incorrect.
I have never seen a 2500HD with an Automatic t-case.
Originally Posted By: PT1
If you have an "auto 4wd" button on your tcase you need the GM autotrak II tcase fluid. If you only have the 4lo, 4hi and 2hi buttons on your tcase it gets Dexron III. Your diffs get 75w90 synthetic.
Thats exactly what I have. I was told to make sure to use Synthetic Dex III in the transfer case. Yes for the Syn????
Based on what the OP highlighted here I would think he only has the three buttons 2hi,4hi and 4lo which is the electrically shifted version of your floor shift Not an "Auto". You stated anything push button gets the Autotrac II fluid and that is incorrect.
I have never seen a 2500HD with an Automatic t-case.
IIRC, only 1/2 ton GM trucks were available with the Autotrac option. You could get a 3/4 ton Suburban with Autotrac though.
Originally Posted By: Just1More
I DO NOT have the AUTO button..
Then ATF for you!
I DO NOT have the AUTO button..
Then ATF for you!
Originally Posted By: Zaedock
IIRC, only 1/2 ton GM trucks were available with the Autotrac option. You could get a 3/4 ton Suburban with Autotrac though.
+1 I tried to edit my post to say this may be an exception.
Also, there may be some 2500HD Sierra Denali p/u's with the option (not sure though)
IIRC, only 1/2 ton GM trucks were available with the Autotrac option. You could get a 3/4 ton Suburban with Autotrac though.
+1 I tried to edit my post to say this may be an exception.
Also, there may be some 2500HD Sierra Denali p/u's with the option (not sure though)
Originally Posted By: Whitewolf
You need to figure out and tell us which T-case you have. Get under there and find some information. Sorry but it's not easy since there are a number of T-case fluids.
+1 There should be a New Process gear badge on the back side of the tcase with the model number stamped on it. But if you don't have an auto4wd button then it's an electric shift and takes dexron or equivalent. If all else fails...take your vin number to a dealer. OR drain out the old fluid. If it is red...it's dexron if blue...autotrakII.
You need to figure out and tell us which T-case you have. Get under there and find some information. Sorry but it's not easy since there are a number of T-case fluids.
+1 There should be a New Process gear badge on the back side of the tcase with the model number stamped on it. But if you don't have an auto4wd button then it's an electric shift and takes dexron or equivalent. If all else fails...take your vin number to a dealer. OR drain out the old fluid. If it is red...it's dexron if blue...autotrakII.
Last edited:
I plan to change out the diff fluids & transfer case in my 2003 2500HD when it warms in the spring. The truck has 60,000 miles & is no used much lately, garage parked. I have a friend that sells the Amsoil, so I'll give their stuff a go. I cross refrenced the owners manual with the amsoil website to get the corrct fluids. If not for the buddy I would just cross reference & get the fluids locally.
- Status