I had my AX15 rebuilt in December 2011. I could tell afterwards that it was very tight and would grind when going into second gear. I figured I would drive it for a few hundred miles and it became a lot easier to shift. I also noticed that when it was easier to shift it was 90-100+ degrees outside. We had a crazy cold front come through Texas this week dropping temps to 70's. Now the trans is starting to grind a little again. Should I do a gear oil change? What gives? Not sure why the lower temps affects it so much.
I agree with the gear oil diagnosis, I found that out the hard way myself. From my research I've found that Redline MT-90 (GL-4) is a highly recommended fluid by other Jeepers and I myself run it and fully recommend it to others. Change it ASAP as it is not playing nice with your synchros and it will shift worse in cold weather. Chrysler did start recommending 10W30 due to availability of compatible fluids. Do yourself a favor and get some Redline MT-90, four bottles will do as the AX-15 requires 3.25 quarts:
I just got a 97 TJ with 4.0 and AX-15. Everything has been running very well, but there were some signs of lack of maintenance like plugs worn down to 0.045" gap.
This past weekend, I checked the fluid in the tranny, and it was very muddy looking. There were no issues with grinding or anything else. When I changed it, there were very small filings in the fluid. Nothing surprising.
Based on the feedback on the forum, I put in full synthetic 10W-30. Pennzoil because it was available.
After changing the fluid, it now grinds a little bit every time I put it in reverse. No other issues. Any thoughts on the reason for the grinding?
I plan on replacing the fluid again at the next oil change since it was so far gone. This time, I'll try the Redline that folks are also recommending. Any other advice.
I'd replace it with Redline MT90 at your first available opportunity; I've learned that the AX-15 is a very picky transmission. As for the color of the fluid and fine metal shavings I've experienced the same with no issues.