Ace

Starting to think about fluid changes in the trans and transfer case. I saw somewhere they call for 10w30 or ATF in the Getrag, but can't remember if the NP205 wants something else. Any suggestions? Anyone find something that works good/better?

Tks...

JD730

I have gear oil in my transfer case, 85w-90 and it works fine. I think the book calls for 15w-40 engine oil.

The getrag wants 10w-30 sythentic engine oil or something similar of the same viscocity, the guys that run them will know better than I will. And of course you know about over filling it by about a quart, right?

flashgordon

you can us any thing from 10w30 to 90w, depending on the themp and work load!!!
I'm using 80w90 at pressent,just rebuilt mine. thinking a bout trying some 5w30 sythentic with the next oil change. I weary that it will make the tranfer case noisey

torquefan

I've always used gear oil in NP205s. I'd worry about leaks with anything thinner.

bgilbert

Gear driven case = gear oil lube.

apwatson50

I'm using walmart brand synthetic 80-90 "hypoid gear oil"

Boatnik

AMSOIL 75w 90 severe duty in transfer case and both hog heads.

89dieselkong

I tried running synthetic oil in the t-case and it just made it noisy. Like bgilbert says, gear driven t-case+gear oil. I just switched to Rotella gear oil. Much quieter now.

frostie

I had a 1979 ford with a C6 trans and the 205 and it had ATF in it. I ran it that way for about 6 years. On the other hand it is a gear box.
All semi trucks today with 18 speed transmissions come with 50 WT synthetic.
I think ATF is a bit thin.
If you live in cold climate I think any synthetic is the way to go.
I think gear oil is a bit too thick if you live in cold climate.
I have chose to run 50 wt Synthetic in both my transmission and transfer case.
Why? synthetics dont get thick when cold. but 50 WT maintains viscosity when really hot.

Ace

That's the kind of feedback I was looking for. Gear oil is not just gear oil anymore. There are so many variations between different vis, syn, FMs, you-name-it, not to mention climate concerns. I want to pick the right stuff the first time, put it in and fuggedaboudit for a few years.

The PO put RP Maxgear in there, which seems to be doing OK, not noisy or anything. But that stuff has FM's in it, and I think is more designed for the hypoid gears in a rear end. I'm assuming the NP205 is a straight-cut gearset. Anyone know for sure?

Boatnik

The Amsoil web site can give you a print out on all fluids for your particular vehicle.

4x4_Welder

The NP205 does use angled gears, so a hypoid gear oil, or something that can handle shearing like 15w40 Tection or Rotella T is good for it.
In my 72 F100 4x4 I run (ran) 15w40 Tection in the tranny and D21 transfer case. Once I get that truck done, it will be the same stuff back in it.

Ace

Well that's good to know - thanks 4x4! Now I think I can stop worrying about it and just leave it alone for awhile.

timb

90 weight has been good for a lot of miles in mine.