Gearbox Oil 1983 WR500

What make and specification of oil do you suggest I use in the gearbox my WR500 - Im just finishing a complete rebuild

i have used atf quite a bit as the shifting and clutch feel is great with it...the manual calls for 20w and atf is about 10w...i was worried about having the best gear protection.....so i have been running amsoil motorcycle 10w30....seems to work well...if you use a motor oil, make sure its jaso-ma spec, as this means it will work ok with a wet clutch.

walmart sell a non-detergent 30 wt. oil for like $2.49 qt.
Just change it after every weekend out and your tranny will love you especially if your running aluminum clutch plates.
RUWFO:I read somewhere that the viscosity improvers in automotive oils tended to promote clutch slippage, anyone else ever heard that?
I also saw that Husky Fleet runs Cat or John Deer 30 wt. powertrain oil but i couldnt find it anywhere.

You should use detergent oil. The metallic particles and clutch material will adhere to the case rather than stay suspended if non-detergent is used. You should stay away from friction modifiers such as molybdenum disulphide which will ruin the wet clutch. The newer 0w## oils will give you ATF fluid feel while shifting and clutching, but will retain their multigrade functionality. We have tested non-green bottles of Mobil 1 to be wet clutch safe.

I use Motul Transoil in the manual bikes - no clutch drag, no issues.

i'm on ATF - F which is the early Ford Borg Warner ATF, not the gm / later fluid. using in my KTM 300 with good effects as well.

Good to hear what you guys are using - many thanks for the info.