NP 435 4-Speed

[maxmac]

I'm replacing all of the old fluids in my '66 Town Wagon and am wondering what fluid recommendations you all may have. I have the shop manual and is recommends SAE 50 gear oil (I live in Western CO-high desert so it's very warm during these sumer months), but I've seen other posts on this and another forum where members are running 80w90 oil.

Any additional thoughts or recommendations?

[W_A_Watson_II]

I was running 90 wt Gear oil, but it was too thick, hard to shift when cold. I'm now running Lucas Synthetic 50 wt. Trans Lubricant.

[maxmac]

Thanks for the reply. Off to town to track some down!!!

[Alxj64]

I'm running Redline MT90 in my SM465 (GMs duplicate of the NP435) and it shifts better than my friend's ZF-6 in his Superduty. And you have to be careful with the regular blends of just straight up 80-90 as a lot of it has additives that will eat the bronze syncro rings in the transmission and then it will surely shift like junk.