I used the NAPA house brand GL4 after I rebuilt my AX15. I was thinking I would run the cheap stuff for a week until the new synchros and bearings settled in, drain it, and refill with the good stuff. It shifted so bad with the NAPA stuff I thought I buggered the rebuild. I couldn't get it into 1st gear without it grinding when it was cold!
I almost pulled the tranny back out, but instead I drained it 3 days later and put in the RedLine. The difference was like night and day. The Redline shifted very smoothly, especially when cold. BTW, the NAPA GL4 has some sulfurs which will shorten the life of the brass synchros.