It's a replacement. I don't know about the XJ's manual at all (requirements, etc), but in my other car (known for transmission problems) I run it in it. So far (about 30k miles and it's been pretty smooth...
Though one would wonder... what is your problem with your transmission as it is now...
shifts are very rough and takes alot of time to go into gear. doesnt want to shift at all when cold. 5th always grinds, dont know why. im going to check linkage on clutch and maybe replace clutch fluid also.
I just found this information. "This description makes Synchromesh suitable for use in some transaxles or transmissions where GL-4 gear oils are specified" http://www.stealth316.com/2-pennzoil-synchromesh.htm
I kept looking and came upon this archive. http://www.naxja.org/forum/archive/index.php/t-2811.html Its very long and confusing. im still not sure what to use. chixjeff might find the info on here to be helpful stating that the 96 and older trans require GL5.. but some say it was a typo in the manuals.... not sure what to do.
I just found this information. "This description makes Synchromesh suitable for use in some transaxles or transmissions where GL-4 gear oils are specified" http://www.stealth316.com/2-pennzoil-synchromesh.htm
ROFL, Jeff Lucius article! That article was written with my other car in mind (Stealth RT/Twin Turbo), the one that I run the Synchromesh in. A lot of great articles on his website, but most are written with the 3000GT / Stealth in mind.
The "compatibility with yellow metals" is key. AX15 manual transmissions use soft metal synchronizers, aka "yellow metals." The sulfur additives in GL5 rated oils will eventually corrode those away.
I run Redline MT90 in mine, and have for the better part of 10 years. No complaints from me, and the synthetic helps a lot in colder climates.
The "compatibility with yellow metals" is key. AX15 manual transmissions use soft metal synchronizers, aka "yellow metals." The sulfur additives in GL5 rated oils will eventually corrode those away.
I run Redline MT90 in mine, and have for the better part of 10 years. No complaints from me, and the synthetic helps a lot in colder climates.