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AX-15 fluid type?


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Read in the owners manual that I need 75w-90 GL-5 grade lube. But I remember reading somewhere on here that it changed due to synchro problems with that lube, but I'm not entirely sure. Should I put 75w-90 into my trans or is there a different fluid I should use?

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Not to contradict, but better read this:

http://www.amsoil.com/articlespr/2007/a ... asics.aspx

 

I have been doing some digging on this subject and it looks like the bottom line is you need a GL-3 (if you can find it) or GL-4 compliant GEAR LUBE. They lack the sulfur additives that GL-5 gear oils have, which is what protects your brass syncros. The GL-5 adds sulfur for the added shear protection and high pressures found in hypoid (ring and pinion) gears. The engine oils DO have nearly the same viscosity (SUS not kinematic) as these types of gear lubes but not the additives that will withstand the pressures experienced in a gear on gear situation like in your tranny. There is a property of fluids called "bulk modulus", which is simply the compressibility of a fluid. In general practice, fluids are considered non-compressible (why hydraulics work), but in extreme pressures they can be. Haha, taking a fluids/hydraulics class in school right now.

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Jeep used to carry a GL3 fluid specifically for the AX-15. They discontinued it and now say that 10w30 is what you should put in it. After all the problems early on, I gotta imagine they were careful about it. Also, for the short time I drove the 90, everything worked just fine. The shifting was much improved, but then the oil that came out was pretty nasty.

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My trans was rebuilt about a year ago, so it should still be in good shape. I have no idea what fluid was put in after the rebuild (I didn't do it as it was beyond my ability at the time) but it is about time to change out the oil, and I had no idea what to put in it. I don't really want to rebuild the trans again because of eaten synchros, so I am hoping that GL5 fluid wasn't put in after the rebuild.

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I use nothing but Redline MTL for my manual transmissions. Both my Cherokee and Wrangler have the 3550, and the Comanche has an AX-5 waiting to be installed. Safe for brass synchros.

 

http://www.redlineoil.com/product.aspx?pid=45&pcid=7

 

Both 3550's have over 125k on them with this fluid and they both still shift and drive "as new". :thumbsup:

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  • 5 weeks later...
I'm going to be changing out the fluid in my 4wd trans soon. Does anyone know how many quarts I'll need off hand? - I don't have my book accessible right now.

 

Thanks in advance.

I just changed my transmission oil to the Redline MT90, and it took a little over 3 quartz. BTW it now shifts flawlessly with no cold reverse grind, or difficulty getting it in first gear.

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If you don't want to pony up for the MT-90, Penzzoil Synchromax is also supposed to be synchro safe. I used it in my last change to flush what the previous owner had in there (smelled like ATF coming out), I had lots of grinding and difficulty getting it into first. It's smooth now. In the future I think I'll try the MT-90 to see if it improves further.

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