Reference: Manual Transmission Oil

[Wayne Hingley]

Having recently changed the transmission lubricant in my M38A1, I realized I hadn't considered whether my oil had EP additive in it or not, as I wasn't aware most newer oils (GL 4 & 5 certifications) contained EP. Its not well identified on some containers, so you need to look at the specifications to see what additives are in the oil and what compatibility notes are outlined by the manufacturer.

Sure enough the oil I used contained an EP additive. I have now drained my transmission and transfer case (along with my steering box and PTO/winch), and flushed them out, and refilled with a non-EP yellow metal compatible oil.

My jeep had less than 100 miles on the EP oil, and I already had signs of breakdown of some brass components (see photos below). The first photo is the oil that I drained, and the second is the "flush". You can see the brass on the bottom of the drain pan.

I hope others will check their systems, and avoid the types of failures noted by Robert and Lynn.

My transmission is still working perfectly, so I think I was lucky to take action before too much damage was caused.