• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

Transmission and transfer-case identification help and fluid help.

NateDogg024

New Member
Messages
21
Reaction score
2
Location
Northern Illinois
I'm getting close to having the truck all back together and I'm trying to find out what trans/t-case I have, so that I can replace the fluids in them. So fare Ive found a lot of different info about what fluids to use and Ive also noticed that there is a lot of different fluids used I various years makes and models. Could I please get some help from you all. I really don't want to end up using the wrong stuff and damage anything.

Also, this may be a dumb question, but while I'm here I might as well ask. Is the fluid in the t-case separate from the trans or do they share fluid?

I'm fairly confident I have a NV4500 trans but not 100% sure.
I have know idea what t-case I have.

Stats are as followed:
Year: 1993
Make: GMC
Model: K2500 pickup
Engine: 6.5LTD
Trans: ???
T-case:???

Thanks for reading.
 
Look on the back of the t case for a round id plate about the size of a silver dollar.
if loosing fluid from the transmission into the tcase , your output seal of the transmission needs replacing.
 
So there is a way for the fluids to mix. I was just curious because when I removed the drive shaft I was wandering if it was just t-case fluid or both.
 
Look on the back of the t case for a round id plate about the size of a silver dollar.
if loosing fluid from the transmission into the tcase , your output seal of the transmission needs replacing.
GM didn't use a seal on the output shaft of the transmission. The input shaft of the transfer case used 2 seals early on, but later on went to a single double lip seal, and a gasket at the transfer case mounting flange. I have yet to see a GM in this era with an output seal on the trans side in a 4X4. Your tranfer case is most likely an NP241 which uses ATF DEX3 type fluid, but you can substitute a HIGH quality 5W30 diesel rated motor oil in the transfer case. As for your trans, if it is a NV4500, then the GM fluid is your best bet. There is a couple of aftermarket fluids they say will work, but cost wise it isn't mcuh cheaper than the GM stuff you know is right.
 
The transfer case should have a drain plug and a fill plug. The New Process / Venture had them on mine.

The transmission might not have a drain plug in which case you use one of the bottom PTO cover bolts as a drain.
 
if its the 93 in your signature, you have the NV4500.

It requires GM part number 12346190. it is a special 75w90 full synthetic oil that has a special additive package. It is actually Castrol Syntorq LT (NOT to be confused with the off the shelf Castrol Syntec) under the Castrol Syntorq label, I think the smallest container available is a 15 gallon drum.

This outfit buys it by the 30 or 55 gallon drum and re-packages it for you in 1 gallon or 2.5 gallon jugs. same exact oil as what is in the GM 12346190 quart, but bulk quantity and much cheaper per quart.
http://www.ebay.com/itm/Manual-Tran...500-/361198567152?hash=item54191cbef0&vxp=mtr

The only substitute that comes close is Amsoil MTG. in top-off situations, the Amsoil has worked flawless, but i did a drain and refill on a 250,000 mile NV4500, and shift quality suffered, so I went back with OEM oil and now it shifts fine. In a lower miled unit, I bet the amsoil would be fine.

If you tow heavy, consider adding finned aluminum PTO covers. there is FAST covers sold on ebay or via Geno's garage, or if you want to do the old fashioned way, you can mail a check to Gear Tech HD. I am personally running the Gear tech covers on my 93 K2500HD, and have the FAST covers sitting in a box waiting to go on another unit.

The NV4500 builds alot of heat, so it is best to run PTO covers if you tow at all.




The t-case like mentioned above should be a NP 241, big fill and drain plugs on the back of the case, Use Dexron III, aka ATF.

Also like said above, the seal to keep everything seperate is the input seal on the t-case. Due to the heat built by the NV4500, this seal gets cooked and prematurely fails. considering running the finned PTO covers just for the reason of prolonging seal life. Either I am a wuss, or dropping the t-case outside (luckily on a cement pad) with no lift is not fun, so I dont want to do it again for a while. :)
 
Back
Top