What fluids do you guys use in your manual 4-speeds and NP205?

 

Gear oil.............I have used 80W90 as well a 85W140 successfully..........no real preference........

 

I use lucas 80w90.

 

I use Valvoline 80w90 conventional gear oil for both. I prefer conventional anything over synthetic for these trucks.

 

Valvoline 80w90 gear oil in the NP435 and NP203. Smelly sulfur stuff!!! Wear latex gloves if you can...

 

I'm running Mobil One Synthetic Gear Oil LS 75W90. This shifts much better in cold weather.
The original factory fill was 50w motor oil, to be topped off when needed with 90w gear oil????

 

Synthetic or conventional? I live in the Pacific NW so it rarely gets in the 90's in the summer and it rarely gets below freezing in the winter. Write now second gear can be a bugger to get into, especially when a Lexus is crammed up my tail pipe at a stop lite. It drives them nuts when I'm trying to find a gear. Puts a smile on my face.

 

My 1976 owners manual says SAE 50 weight for both the 4 speed and the transfer case, unless below 10 degs, then use SAE 30

 

That's egine oil which is equivelent to 70W90, or more readily available 80W90

Josh

 

We just put 85w-140 in my buds np435 and np205. And it shifts sooo much better. But im pretty sure the PO had ATF in both... Fail lol...

 

I put ATF-4 in my Jeep's transfer case put ATF has detergents so I figured that wouldn't be good in these older trucks. I'll just through in some 80W90 and move on. Thanks for your help guys. I appreciate it.

 

I've had good success with Valvoline Racing SAE 60 in both trans and tcase (np435 and dana 20)