Transmission Oil Weight ? 4 speed

[Vermont Rocket]

70 Roadrunner, 4 speed. Factory shop manual says Hypoid 140 weight, but a few other sources say 80-90. Your help is appreciated, Rocket

 

[69hemibeep]

Any of those are fine, its is said they shift slower with heavy oil and its true cold but warmed up I can't tell the difference. They came with ATF in them but I use Pennzoil Syncrosomething or another which looks like 50w.

 

[quikbird]

Personally I use Lucas 80-90 and have had no issues. Remember they all stink and make a hell of a mess.

 

[mahoney0_00_3]

they put atf in them to save on drag and get better MPG---I have had both and the 80 90 is good----only old school oil don't put synthetic or it wont work with the sinc and it wont shift right