hi, does anyone know what weight oil to run in an old 4 speed ?&nbsp\\; and do you fill it to the little allen plug on the right side just behind the kicker?&nbsp\\; thanks!

 

Back in the day, I used to run just 60 wt. oil in the transmission. The same stuff I ran in the engine. Nowadays, folks like to run gear oil. If you use an 80W-90 gear oil you will be fine. If it leaks, use the cheapest oil you can find until you fix the leak. Fill it to the bottom of the threads of the fill hole and that will be plenty. Fill it with the bike standing up straight, not on the kickstand.

 

that is what someone else told me too, but i thought i would just see what other people had to say as well.&nbsp\\; thanks!

 

1980 FXWG
I use the same oil I use in the engine. If I use heavier oils trans seems to shift

harder. It is also harder to find neutral. I fill my trans to the threads for the cap.

My cap is on the top of the tranny. Just my 2 hope it helps.

 

I am using Harley Formula Plus.&nbsp\\; It shifts well and cost $6-$7.

 

I've always used 80-90 in mine.

 

80-90 gear oil in my 82 FLTC 5-speed.

 

When the 4 speed came out in the 30's Harley warned against using gear oil and to only use motor oil.&nbsp\\; I've used both and haven't seen much difference.&nbsp\\;&nbsp\\; If you have an old kick cover fill it to the threads in the filler opening.&nbsp\\; If you have a newer cover remove the allen screw plug and fill until it just runs out.&nbsp\\; Both covers require the bike to be upright when you fill it.&nbsp\\;
&nbsp\\;
If you live in a cold climate make sure you put lighter oil in the tranny during the winter.&nbsp\\; I found out the hardway that if you go from South Florida to Tennessee in November.&nbsp\\; At 20 degrees&nbsp\\;70 wt don't work once you let the bike cool off.&nbsp\\; The dip stick looked like a tootsie roll the next morning.&nbsp\\; You could stand on the kickstarter it wouldn't move.

 

I use Belray 80/90 gear oil in my 75 superglide, it is red so if you ever do get leaks you can distinguish from motor leaks.

 

Thread is 14 years old BTW.