4 speed oil

[68-500]

Guys get to worked up about this. I would just make sure its got a proper amount of lubricant in it. Its a manual transmission in a light weight vehicle that will most likely never be worked hard for extended intervals. Its gears, roller bearings and synchronizes. Anything from ATF to 85-140. If you don’t like the way it shifts try a different lube.

 

[440+6]

I always used gl4 140, then replaced the guts with passon 4 speed overdrive,
Had the gear installation done by liberty gear, they also modified the blocker rings with square blockers among several other small modifications, anyway it wasent shifting great and Paul at liberty told me to use atf and dont worry he guaranteed no problems.
I went with 2 qts of gl4 90w and 2 qts atf. Within maybee 20 miles it started shifting very smoothly.
Still 50 50 years later and perfect shifts always.

 

[Krooser]

The Chrysler manual was written before synthetic oils were designed for use in street vehicles. Viscosity was the main issue back then, and still should be today. Trust the engineers, synthetics work great in rice-burners and disposable grocery-getters. If you want to protect an old, expensive collector vehicle, use conventional and change it regularly.
So there...Just my 3cents.

As far as GL-5 eating yellow metals...I don't think anyone can say this for sure. It's still an up-in-the-air issue for now.

When I was a British Triumph collector I had a TR3A trans with GL5 lube... the brass syncros went cafluey in 5 years.

Used GL4 from then on... I found a Mobil wholesale house that sold me the GL4 at 1970's prices since that's how old his stock was!

 

[dadsbee]

I always used gl4 140, then replaced the guts with passon 4 speed overdrive,
Had the gear installation done by liberty gear, they also modified the blocker rings with square blockers among several other small modifications, anyway it wasent shifting great and Paul at liberty told me to use atf and dont worry he guaranteed no problems.
I went with 2 qts of gl4 90w and 2 qts atf. Within maybee 20 miles it started shifting very smoothly.
Still 50 50 years later and perfect shifts always.

Nice! I'm running 20W50 engine oil in my Bee. Best that it has ever shifted in my lifetime and that's 49 years of me driving the car... transmission has never been apart. My 66 Sat's 18 spline shifts like ****, my next job is to dump what ever is in it and do the same with it. Wife's Formula S may be next...