Transmission oil

What will be the best transmission oil for the 5-speed box, manual says SAE90, thinner SAE80 or SAE 75W80 (semi synthetic) will be better.May be smoother, better shifts w/o gear scatching will be possible. Trans only (not transfer case)takes 6.5 quarts?

I used 80/90 weight gear oil in mine. It was what the manual said to use. It is thick and sticky and works great but is kind of expensive. I bouthg 5 gallons and didnt need it but have it. Same thing you should put in all your axles to. Make sure those arnt low or you will be in for one fun job.

thanks for information.today i flushed the transmission, tranfer case with engine oil/diesel mix....small amount of metal layer came out,
but should be not a problem I think.

Ain't no gear oil o the planet gonna he with shifts.. you can either double clutch or you can't.

During the War most, if not all trans/transfer oil was 90 weight. Army Motors (the real one) had a big write up.

You do realize this is the CCKW forum? Ain't no semi-synthetic in any manual I own.