Replaced my TFI unit this weekend and did the trans oil while I was at it. I have the 4 speed Tremex with overdrive. I was running 85-90 Sta-Lube and it didn't shift that great. Notchy feel, not smooth. I switched to AMS Oil 75-90 synthetic and it made a huge difference. Just an FYI.

 

There are a few of us the use Amsoil products.

 

I'm one of the few now. Good stuff. I'm going to put the rest of the Sta-Lube in my jeep transfer case that has a slow self-changing feature (leak).

 

I used Red Line MT-90 in my NP435 and the Advance Adapter over drive.
You have to look over the normal 85-90 wt oil you get that is is GL-4 or lower.
Most you find are GL-5 and they say that is not good for yellow metal like brass bushings and shift rings.
Dave ----

 

That is a benefit of using amsoil, all their gear oils are safe for yellow metals. No guessing.

 

Red Line is the same.
Thing is you cant find either oils at parts stores
Dave ----

 

You can become a preferred member at Amsoil. I did that years ago. I get my orders the next day. My local NAPA also carry's Amsoil. You can find dealers near you on their website.

 

2nd what max stated above. Shipping is fast. preferred member pays for itself.
I wait till they have a promo on shipping and make an order than.

 

The Sta-Lube 85-90 is synchro safe (bronze metal safe). It's just not working well with the synchros in the tranny. The synthetic stuff, either brand, AMSOIL, Redline is the ticket. Much better shifting and the AMSOIL bottle states that it is synchro safe.

 

Brad Penn for me!

 

I know they make motor oil didn't know they also did gear oil.
Dave ----

 

My dad was a mechanical engineer in the early days of the aerospace programs and we were a Valvoline family for what seemed forever (as far as gear oil) and I continued with that for a few decades until a couple of years ago...... although i still run Valvoline Mercon V in my autos, Valvoline has been busted by numerous entities (including California) for their products not meeting oem spec as advertised. What made me "run" away from them was abouth the same time I topped off my 1965 Mustang t10 4 speed with 2 ounces of what was suppose to be GL4 spec oil.... within just a few miles there were shifting issues never seen before with this tranny......... brass/copper bushing swelling, etc. I did a full wirte-up on this in the "Classics Section" but in short, we verified that there was no mechanical related issues, so I dumped the tranny oil, flushed it with one fresh quart and refilled with BP GL4 spec oil........... shifts as smooth as silk...actually better than I have ever experienced (and the car has been in our family sice new, I bought it from my folks in 1986, did a ground up rebuild which took a year).

Can't say enough about BP and their engineering staff! They even ran an oil analysis on my oil for free just to help me verify this was "Chemical Related" and not mechanical.

 

Please see this thread for more info on The Great Gear Lube Debate:

https://www.ford-trucks.com/forums/1...sion-lube.html

Specifically, see post #8 for some research I did about 3 years ago. I went with Sta-Lube GL-4 gear oil. The nice thing about this brand is it is readily available at NAPA and other retailers. No need to special order it or join the Amsoil cult.

 

He used sta lube originally if you read the thread. It wasn't working out for him.

 

Good catch. I wonder if he was originally using GL-5...