manual trany fluid

So I just bought an XJ with a 5spd in it. Its a 91, so would that mean I have a ax-5 or ax-15. It grinds gears when down shifting if the rpms are above 2 grand. I am assuming the fluid has never been changed and it may help the issue. Correct me if I am wrong. But, my question really is what fluid to put it in it. One better than the other? Pictures or what the container looks like, or links to buy the correct kind would be greatly appreciated.
Thanks in advnace.

You should have the AX-5, the 15 was only used with 4.0L...

If you want the best fluid, IMO, go with Amsoil!

http://www.amsoil.com/storefront/fgr.aspx

If you have a 4 cylinder it's the AX-5. If you have a 6 cylinder it's the AX-15. I used Red Line MT-90 from Summit Racing in mine. It fixed all my shifting problems. HTH.
http://store.summitracing.com/partdetail.asp?autofilter=1&part=RED%2D50304&N=700+115&autoview=sku

I second the MT-90 choice.

Ditto on the RedLine. Regular auto store GL3 or GL5 will shift like crap and the sulfurs in the GL5 like to eat brass synchros. The Redline made a world of difference for me.

For the guy blindly pushing AMSOIL, you should not be recommending it for the AX-15. It's a GL5 gear oil meant for differentials. It's extreme pressure (EP) additives are primarily sulfur which starts attacking yellow metals such as brass synchros when heated above 250*F.

I also recommend Redline MT-90

It has friction modifiers in it to help synchros engage better and quicker and prevent grinding, sounds like what you exactly need.

It is a Synthetic GL-4 Fluid, BUT, the literature states that it won't become corrosive to brass/bronze synchros until insane temps like 450°F.

The OEM recommended fluid is GL-3 Gear Lube. There was a mistake in a lot of the owner manuals that recommended GL-5, which is a big NO-NO. GL-5 and GL-4 (to a lesser extent) have high pressure additives that can become corrosive and damage the Synchros at high temperatures.

Gear Lube has NO friction modifiers, but many manual trans don't need them, some do, but friction modifier in a manual trans, whether needed or not, can improve the shifting by helping the synchros engage quicker and smoother.

The Redline MT-90, although a GL-4 Fluid, is synthetic and can handle heat much better, so no one has had any problem with MT-90 damaging synchros like GL-5 and other GL-4 fluids have.

i think i might put some of that in there...

I have a 4.0 so I have the ax-15 then? is what I read.

where do I get this redline stuff at? and so this redline stuff already has this midifier stuff to help the synchros?

Yes the 5-speed manual behind the 4.0l is the AX15 (the 2.5l has the AX5). There are a number of online dealers. Last time I bought some it was $8 a quart. You might have some race shops in your area as well.

Redline Oil said:

Red Line Oil's MTL and MT-90 are designed to provide excellent protection and improved shiftability for manual transmissions and transaxles, having cured the problem of hard shifting in thousands of transmissions with shifting troubles. How? They have the appropriate coefficient of friction for most manual transmission synchronizers (many gear oils, engine oils, and ATFs are too slippery for proper synchro engagement).

Click to expand...

Where to buy?
http://www.redlineoil.com/dealers.asp