Which fluid for Jeep transmission?

[Jason280]

I'm getting ready to change the transmission fluid on a '94 Jeep Wrangler. This particular Jeep is a 6cyl with the AX-15 5spd manual, and I doubt the fluid has ever been changed (150K+ miles).

The service manual calls for 75w-90, but it looks like the new standard is to use plain old 10w30 motor oil. Now, I have 3.5qts of Pennzoil Syncromesh, and I am curious if it will be satisfactory to use in the Jeep. Any reason I can't use Syncromesh? Also, outside of cost, any reason why plain 10w30 would be better? Thanks!

 

[Dakota1820]

i would us 75w90

 

[Rand]

make sure if you use a 75w90 its GL-4 and made for transmissions.. the right friction modifiers etc

 

[hounddog]

Wrong properties will damage brass and certain metals in manual transmissions. Make sure and use the correct fluid.

 

[toneydoc]

Use what the manual calls for. Will last longer that way.

 

[caravanmike]

the manual calls for gear oil (gl4) but was superceded by jeep because of sulfer in gear oil (gl5) not being yellow metal friendly and gl4 being hard to find. most dealers are using 10w-30 in the ax-15,ax5.

 

[Donald]

Look up on the Amsoil website for your vehicle. You cannot go wrong with Amsoil.

 

[SOHCman]

Redline MT-90 (75w-90) is another GL4 premium gear oil that would serve you well. As for the synchromesh it would be too thin, I believe it's a bit thinner than a 5w-30 iirc and is more suited for a passenger car transmission, not a heavy duty application like a jeep.

 

[jake88]

I would find a good API MT-1 or SAE J2360 gear lube. They meet all the rig and bench tests of GL-5 plus the ASTM D130 test for copper corrosion. You are looking for a "1a" copper strip rating