For those that have changed the gearbox oil, what is the procedure? Fill plug only? Is there a drain plug? I think I still have a pump laying around if I can't drain it... Won't be able to look at it until I'm swapping out the oil, and I'm gonna be in a hurry tomorrow when I do it...

 

I used Synchromax in the TR6060 in my Shelby and it's performed admirably in everything I've asked it to do, including daily driving and in early-morning cold shifts. I would imagine both the Amsoil and RP gear oil will both be an improvement over the stock stuff, so pick your preferred poison.

Edit: the RL oil I believe has more zinc in it. I know the motor oil does, and it does help with friction abatement there. Not sure if it's quite as noticeable/necessary in the gear box. I don't use Redline stuff, but not because I have been warned off it. I'm sure it has its good and bad points just like everything out there.