Hey guys, I have a Ford LN600 4 speed dump truck, like a F600 truck. I want to change the transmission oil and don't really know what to use for the best service.

I figured it had 80/90 gear oil or automatic fluid. It doesn't shift smooth when it gets hot, especially first to second or neutral to first, and it grinds a lot.

Would a fresh change to syntheic oil help my shifting?

Any help or suggestions would be great.

 

I cant imagine a dump truck running ATF in the stick trans. Did you drain it and see and color indications? I would imagine 80/90 kinda thing but wouldent stake my bad reputation on it.