So I’ve got Redline Shockproof in the trans now, but its a little low. I’d like to top it off but I can’t get Redline locally and I’m leaving on a trip before Amazon would get it here. Would any other oil be compatible with the Redline? Maybe just pick up a quart of Mobil-1 75W-140 or some Mobil-1 20W-50 and add an ounce or two?

 

If I would mix anything with shock proof it would be ATF. That's basically what it is with additives. I had a used quart around for couple years, when I just went to pour it out it looked like trans fluid at first, all the heavy stuff had settled. Just get some amsoil or mobile one ATF to top off

 

No offense but that’s not a very scientific observation. I wanna make sure I use something that’s chemically compatible, not based on what it looks like.

 

You could dump what's in there out and replace it with something else that is readily obtainable.

 

I'm sure he could mix oil, gear oil or trans fluid and it would be fine. I mix my primary with amsoil primary and amsoil ATF. I have tried other stuff but from my none scientist eye this is the best I can find for both wear and shifting ease.

 

Do you really want to put atf in a harley transmission? There's gears in there no clutches or torque converters. Why not just dump it and fill with something that's made for that purpose? You should be able to find some Mobil gear lube pretty much anywhere. But it's your bike and some guy on the internet said it would be ok so what could go wrong?

 

96 Ford truck stick shift came from the factory with ATF. I put 200,000miles on that truck before selling, never had the trans apart.

 

I probably would not add ATF, although my '07 5.9 Cummins /w 6 gear trans uses it and has been fine for many thousands of miles. I would just top it off with some normal gear oil of approx same viscosity. Better would be to just dump the quart and replace the whole thing as mentioned above, but for a quick top up I don't think a small amount of any GL5 oil would in any way hurt anything.

 

Thanks for the input fellas. I think I’ll just swap it out with some Mobil-1 gear oil. Was just curious about the compatibility of these lubricants.

 

Well you could do a test. With the drained red line and get back with us. Like I said I'm sure you'll find they all mix. It's not like one is lacguer and the other enamel paint.