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AX 15 Gear oil?

I’ll like to know too.

I read all kind of things people put in them :laughing:

5W-30 (allegedly must be mobile 1 oil??)

Pennzoil synchromesh

$$$ and rare oil you use in NV4500, can be used in ax-15 too.

Mt-90

Sae 50 oil

10W-30 whatever oil

Gear oil of some kind.

Etc.



I haven’t change my ax-15 oil… because wtf am I to refill it with and it’s working fine now anyhow
 
This is what Novak has to say :confused:

Transmission Fluid​

The factory manuals call for 75W90 GL-3 gear oil for the AX15 transmission. This fluid is essentially obsolete; superseded by GL4, then GL5. However, many GL5 fluids have friction modifiers that are not compatible with synchronizers, so make sure to check for compatibility.

It is the experience of some that a 50W fluid provides quicker shifts and especially so in colder climates.
 
Last time I filled one, I used synchromesh sped'd gear lube.

 
I went down this rabbit hole a long time ago and read way to much shit lol. I found somewhere in that hole that a straight SAE 30 synthetic is yellow metal safe and has the correct specs that these trans require. So for the last 5 jeeps ive owned, Ive swithed the trans oil to mobil1 sae 30 synthetic and they all shift like butter. Even the 1 i had that didnt shift so great when i first got it shifted like new after i swapped the gear oil out of it.
 
I went down this rabbit hole a long time ago and read way to much shit lol. I found somewhere in that hole that a straight SAE 30 synthetic is yellow metal safe and has the correct specs that these trans require. So for the last 5 jeeps ive owned, Ive swithed the trans oil to mobil1 sae 30 synthetic and they all shift like butter. Even the 1 i had that didnt shift so great when i first got it shifted like new after i swapped the gear oil out of it.
This?
1679028764512.png
 
This is what Novak has to say :confused:

Transmission Fluid​

The factory manuals call for 75W90 GL-3 gear oil for the AX15 transmission. This fluid is essentially obsolete; superseded by GL4, then GL5. However, many GL5 fluids have friction modifiers that are not compatible with synchronizers, so make sure to check for compatibility.

It is the experience of some that a 50W fluid provides quicker shifts and especially so in colder climates.

Yup. Typo in my last post, i meant SynTrans 50.

Also available in 75w90
 
The concern of oil attacking yellow metal is because of the EP (extreme pressure) additives.

That's why gear oil and transmission gear oil are separate products.
 
There was a tsb years ago that said not to use the manufacturer suggested gear oil.
Gear oil is what I'm seeing with a quick search. What does the TBS spec?

Engine oil normally isn't a good substitute as it doesn't have the proper additives for high pressure like gear teeth see.
 
Gear oil is what I'm seeing with a quick search. What does the TBS spec?

Engine oil normally isn't a good substitute as it doesn't have the proper additives for high pressure like gear teeth see.
An engine doesn't produce pressure on parts that are protected by a thin layer of motor oil?
 
An engine doesn't produce pressure on parts that are protected by a thin layer of motor oil?

How much torque does it take to rotate a camahaft. What's the contact patch of a pair of timing gears?
 
How much torque does it take to rotate a camahaft. What's the contact patch of a pair of timing gears?
Uh crank shaft? You guys run your "gear oil". I've got a decade of shifting on a 91 yj with 30w synthetic in it.
 
I got all fancy and put this shit in.

0000256_mtl-75w80-gl-4-gear-oil_464.jpeg


No idea how it works yet, but it seems to shift nice without the motor running.
 
Uh crank shaft? You guys run your "gear oil". I've got a decade of shifting on a 91 yj with 30w synthetic in it.
I'm not saying you're wrong. Tons of old iron 3/4/5spd transmissions ran 30/40/50w motor oil.

But engine bearings have nowhere near the PSI load on them that gears do since they don't have two relatively small radius surfaces rolling over each other.
 
I got all fancy and put this shit in.

0000256_mtl-75w80-gl-4-gear-oil_464.jpeg


No idea how it works yet, but it seems to shift nice without the motor running.

That's what the Chevron SynTrans I mentioned is. Several other brands as well, but I mostly deal with Chevron and P66.
 
Uh crank shaft? You guys run your "gear oil". I've got a decade of shifting on a 91 yj with 30w synthetic in it.
I deal with lube oils on a large scale and it's interesting how some shops pick what they use.

It's a challenge figuring out the proper lube for some stuff. Especially when digging in the rabbit hole to find any manufacturer info, why a specific brand/type which hasn't existed in years was spec'd etc.

Engine oil is designed to handle combustion byproducts and there's generally less pressure in parts vs in gearboxes.

I can think of several other oils that would probably work in a transmission.
 
I deal with lube oils on a large scale and it's interesting how some shops pick what they use.

It's a challenge figuring out the proper lube for some stuff. Especially when digging in the rabbit hole to find any manufacturer info, why a specific brand/type which hasn't existed in years was spec'd etc.

Engine oil is designed to handle combustion byproducts and there's generally less pressure in parts vs in gearboxes.

I can think of several other oils that would probably work in a transmission.
I do know that if your engine oil is JASO certified it has the pressure additives in it for gearbox use. I like using Rotella 5W-40 for this reason, I have a couple of rigs that run that in both engine and transmission, mostly high-miled Jap rigs that regular trans oil changes get the "iron" these things start to create after 100k out on a regular basis is beneficial.

I know one thing: All my Jeep friends run 80w-90 GL-5 (because its cheaper than 75W-90 synthetic) because the owners manual says gear oil, and they have constant transmission issues with their AX5s/15s and I cannot convince them otherwise, even though my Toyotas run the same trans and I typically run good engine oil in them and never lose them. Of course, they also don't reroute their vent lines and are constantly swamping them with water and not changing it right after:homer:
 
It's certainly overwhelming when looking at options.

We have a greybeard at work that digs into lube specs as a hobby. Dude is like Rain Man in this stuff.
 
Another one that i was thinking of is Chevron Meropa gear oil. It's normally used in industrial gear boxes.

Here's good info...

 
So we have 2 that say synchromesh and everyone else has a different opinion
 
I've had Redline MT-90 (75w90) in mine and currently have Redline MTL (75w80) in it. Didn't notice a difference between the two. Shifts ok I guess, not the best but not the worst either. But it hasn't gotten any worse in 100k miles so I don't think I'll be switching.
 
That’s the internet for you. :lmao:

My ax15 is still sitting on the floor waiting to go in so I am just an observer to the discussion
At least mines not on the floor. It's actually mounted. Maybe in a couple years it will run.
 
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