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AX15 temperatures

Lifted straight six

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I have not found any info on what the optimal temps are for an ax15 transmission, does anyone know what temp range is perfect for the AX15? I am not having an issues, simply out of curiousity. Thanks!
 

Gilaguy23

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I dont think there is a optimal manual trans temp long as the lube isnt cooking and coking. A optimal weight oil perhaps for a given climate. If you ran 80/90 in a siberian winter Im sure you'd be having plenty of fun shifting. Run a good synthetic thats dosent turn to mud in sub zero temps and you'd be good to go. Big rigs run diff and trans temp gauges,you could be the first here to see what you get adding them.
 
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freedom_in_4low

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I'm sure those that engineered it know, but without any precise means of checking it and no cooler, I reckon they didn't think it would get hot enough to hurt anything.

That said, as someone who works with temperatures and heat transfer all day at work, I can't help but be curious as well.
 
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Lifted straight six

Lifted straight six

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I'm sure those that engineered it know, but without any precise means of checking it and no cooler, I reckon they didn't think it would get hot enough to hurt anything.

That said, as someone who works with temperatures and heat transfer all day at work, I can't help but be curious as well.

The curiosity is killing me!! I hit it with an infrared temp gun, temps ran about 150-160 in 100 degree weather after a wheeling trip about 80 miles round trip, so i’d say that’s pretty darn efficient! Assumed it would be closer to 200 as it sits right next to the exhaust manifold, but.. tested it 3 different times and got the same temp range, so i’m assuming that’s normal, like i said.. No issues shifting mine.
 
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Lifted straight six

Lifted straight six

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Oct 26, 2020
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arizona
I dont think there is a optimal manual trans temp long as the lube isnt cooking and coking. A optimal weight oil perhaps for a given climate. If you ran 80/90 in a siberian winter Im sure you'd be having plenty of fun shifting. Run a good synthetic thats dosent turn to mud in sub zero temps and you'd be good to go. Big rigs run diff and trans temp gauges,you could be the first here to see what you get adding them.

Yeah, I have been curious to maybe adding one just to see, but I don’t really want to be looking at my transmission temps and worrying about if something were a little off… Jeep stays in Arizona, no siberian winters here. Hell there isn’t even winter. Coldest climate it will see is maybe 25 degrees if I take it up north. I keep an infrared gun on me, that’s my gauge at the moment.
 
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Jerry Bransford

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So long as you're running the right transmission lubricant in your AX-15 there's no need to worry about its temperature. Technically the lube is supposed to be a GL-4 75W-90 but that's next to impossible to find in auto parts stores. Redline MT-90 is a GL-4 75W-90 (synthetic too) but it's pretty much only available online. A GL4 75W-90 is so hard to find that Aisin, the manufacturer, came out with an alternative suitable lubricant which is a synthetic 10W-30 engine oil. No worries about that viscosity seeming to be grossly different from 75W-90, it's essentially the same physical viscosity. Gear lubes and engine oils are measured on two different viscosity scales.

There is one more acceptable lube. SOME GL-5 75W-90 gear lubes are acceptable, but only the ones that say something like "Safe for yellow metals" which means it won't harm the brass synchronizers in a manual transmission. Not many GL-5 gear lubes are safe for yellow metals but it doesn't hurt to look at the back label on newer synthetic GL-5 75W-90 bottles to see if it's safe for yellow metals which means it'd be fine in the AX-5 or AX-15.
 
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Gollywomper

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The 10/30 is a great way to flush out the syncros if you suspect a harmful live had been used. Run it for a bit then install the MT90.
 

Jerry Bransford

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The 10/30 is a great way to flush out the syncros if you suspect a harmful live had been used. Run it for a bit then install the MT90.
I don't know that I'd bother replacing a good synthetic 10W-30 with MT-90. MT-90 is good stuff but the synthetic 10W-30 has been found to be very good too. At least there are no reported issues with it.
 

machoheadgames

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So long as you're running the right transmission lubricant in your AX-15 there's no need to worry about its temperature. Technically the lube is supposed to be a GL-4 75W-90 but that's next to impossible to find in auto parts stores. Redline MT-90 is a GL-4 75W-90 (synthetic too) but it's pretty much only available online. A GL4 75W-90 is so hard to find that Aisin, the manufacturer, came out with an alternative suitable lubricant which is a synthetic 10W-30 engine oil. No worries about that viscosity seeming to be grossly different from 75W-90, it's essentially the same physical viscosity. Gear lubes and engine oils are measured on two different viscosity scales.

There is one more acceptable lube. SOME GL-5 75W-90 gear lubes are acceptable, but only the ones that say something like "Safe for yellow metals" which means it won't harm the brass synchronizers in a manual transmission. Not many GL-5 gear lubes are safe for yellow metals but it doesn't hurt to look at the back label on newer synthetic GL-5 75W-90 bottles to see if it's safe for yellow metals which means it'd be fine in the AX-5 or AX-15.

Aisin didn’t update their recommendation, Chrysler suggested the 10w30 because they didn’t have a 75w-90 GL4 to sell people. Aisin would still advise to run 75w-90 GL4. Personally I just buy the stuff on the internet. I use Ravenol semi synthetic which works well, better than Redline in my experience. I used redline for many years though.
 
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Jerry Bransford

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Aisin didn’t update their recommendation, Chrysler suggested the 10w30 because they didn’t have a 75w-90 GL4 to sell people. Aisin would still advise to run 75w-90 GL4.
I can't imagine Chrysler adding 10W-30 as an approved lubricant solely on their own without having also consulted with the manufacturer, Aisin.
 

Gollywomper

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I can't imagine Chrysler adding 10W-30 as an approved lubricant solely on their own without having also consulted with the manufacturer, Aisin.

I ran it for years in my YJ. Thing shifted great after the switch from regular gear lube.
Had a lube guy tell me engine oil wasn’t formulated for the pressures seen in a gear box. So I use mt90 in my TJ. But I have not seen anyone complain of it either.
 

Jerry Bransford

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Many Jeepers have been running synthetic 10W-30 in their AX-15 transmissions for years without apparent problems. At least they're not reporting problems in the many Jeep forums. And the pressures in a transmission are nowhere near tough like in an axle where a GL-5 is required. Your lube guy is not likely up on all that. I've been told some pretty bizarre/ridiculous things by some lube guys.
 
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freedom_in_4low

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My ax15, which is only a couple of months old, makes a whine noise that I'm not sure whether is normal. I never really noticed until this weekend where I wheeled 6+ hours a day for 3 days straight. I was thinking input or clutch release bearing except it's absent in first gear which makes me think it's the first counter gear bearing. I'm running synth 10w30 but I might try mt90 to see if it quiets down.