Transformation almost done on CJ6 What oil for T18 and D18

Well after a few years of wheeling and dealing and trading parts I am about to fire up the transplanted engine in my 1958 CJ6. I am installing a 1980 Buick even fire v6 mated to a ford T18 tranny and stock D18 transfer case. Seaching the web I came up with mixed results on what oil I should use for the T18 and D18. Should I go with the 80-90W GL5 gear oil (some say use only GL4), or should I use 50W non detergent engine oil? I will be using the jeep anywhere from -10degF to 100degF temperature range.

 

Does it matter if the oil is GL5 or GL4? I have read other post saying GL5 isn't good for the brass bushings inside the tranny.

 

GL-4 is better but GL-5 will work in a T-18. Some of the older tranny's do require GL-4. The 18 transfer case will handle GL-5 just fine.

 

Thanks for the info. I am getting excited to have the jeep running again. Still have to wire the jeep correctly, but for now I am going to do a quick wire job to start it up and work the bugs out of the projects I have done already. I was going to build the wiring harness for the jeep from scratch but I realize the small investment into a wiring harness will save me a lot of headaches down the road. Plus it would be colored coded correctly.

 

I've found much smoother shifts from my t-15 with GL-4.

 

I'd use GL-4.