What Fluid Are You Using In Your Ax15 ?

[Pete M]

there's a drain plug on one side, and the fill is on the other.  

 

 

[gogmorgo]

I wouldn’t add an extra quart. Run what the manufacturer suggests. Running the gears too deep in oil can mess with the splash lubrication, and also runs the risk of aerating the oil, which can cause lubrication issues. Plus it makes a mess when you pull the fill plug to check the level.

 

I was waiting to chime in on this thread until I’d swapped out the trans oil in my ZJ to my prefered Royal Purple Synchromax, because I hadn’t actually run it yet in an AX15. Only in every other manual trans I own. And it’s still my prefered trans oil.

When I bought the ZJ, I don’t know what was in it. The owner’s manual actually calls for 75W90 GL5, and I’m kinda thinking that’s what it was, but this was four years ago and I don’t think I even drove it much before I changed it. I wasn’t able to get any manual trans oils locally or even a gear oil I could guarantee was yellow-metal safe, so I ran some 10W30 synthetic, ran that for roughly two years. It wasn’t the smoothest shifting in the world, but it got the job done.

Then I managed to track down some Redline MT90 that came so highly reviewed, and I wasn’t super impressed. No difference in feel over the 10W30, and while it’s hard to compare directly because I changed it in the fall, I didn’t feel the Redline was shifting as easily in the cold (mornings below -20°F are normal here) as the 10W30 did. It’s also much more difficult for me to get my hands on than the Royal Purple. 
So after a year and a half with the Redline, now I’ve got the Synchromax in my ax15, and it’s a noticeable improvement. At just shy of 200,000 miles I can’t say it’s exactly buttery smooth, but the gears go together much more nicely. It also seems to be running more quietly, but I’m willing to allow might just be my own personal biases telling me things. Shifting is definitely better now though. Even reverse which isn’t even synchronized is going in better than before. And while I don't think we'll be having any more extreme cold until next season, I've historically never had a cold-related issue with it in any other trans, even down below -30°F.
 

As far as the long-ago OP’s asking about 50w oil, I don’t really have the experience to contradict Novak either, but I’m not 100% on what they mean there. I live in a much colder climate than Novak does, and I can’t say I’ve ever even seen a straight 50w gear oil. A 50W motor oil exists, sure, but I once put 15w40 in an AX5 in the winter because it was on hand, and I dumped it less than a week later because it was like shifting through glue, like, push the lever sideways in neutral and it wouldn’t even spring back to centre on its own. I can’t imagine a 50W engine oil would actually improve shifting in anything that hadn’t like, sucked in a pile of silty water, or something.

[pizzaman09]

I too am a huge fan of Royal Purple Syncromax.  Gets my vote after completely transforming the transmission in a 99 BMW M3.  From hard to find gears and notchy to very smooth.  One I get my Comanche, it will be my choice.

[Chad R]

Has anyone used the Amsoil synchromesh?

[Pete M]

you can use anything you want as long as it doesn't have the sulfur compounds. 

[MiNi Beast]

Sweetness, i had to use water to get me home from the swamp. But I atleast use coffee filter to get the alge mostly out. Left some in and its alot quieter now. 

[oleskool]

Redline MTL all the way