SAE 40w Oil in Transmission in M923A2

[purple_duckk]

So I was looking at the Allison manual for the MT654 and unless I'm missing something it looks like SAE 40w oil is approved for the tranny if the ambient temp is 50° F or higher. Has anyone done this?

As I'm down in FL I'd think it would be a good heat sink and not get too thin too fast, but at the same time its a pretty far cry from the 10w that's typically put in it. But I also would prefer to not be the first to try something wacky.

 

[juanprado]

Lots of threads here on best practices for allison lube.
One factor to consider -are you going to carry or tow significant weight?

Mine came with dex 3 already converted by the military. I do not carry any weight and occasionally moderate tow. Very satisfied with my shifting and smooth operation mostly paved and occasional dirt road but no real offroad.

Others like the 15w40 military uses for heavy weights.

Others have speced the allison approved fluids. Transend? Or the multi use tractor hydraulic with allison spec.

All the best on your research and choice. For sure flush well and change filters.

 

[purple_duckk]

Lots of threads here on best practices for allison lube.
One factor to consider -are you going to carry or tow significant weight?

Mine came with dex 3 already converted by the military. I do not carry any weight and occasionally moderate tow. Very satisfied with my shifting and smooth operation mostly paved and occasional dirt road but no real offroad.

Others like the 15w40 military uses for heavy weights.

Others have speced the allison approved fluids. Transend? Or the multi use tractor hydraulic with allison spec.

All the best on your research and choice. For sure flush well and change filters.

Thanks, I've read a bunch of the threads on tranny oil and I saw a ton of different options. Looks like everyone mainly keeps whatever is currently in there. I didn't see anyone try 40w though. I'm going to be doing a full fluids/filters change on my new truck. My plan is to use 15w40 but my thought is the thicker the better for Florida's stupid heat. I have to think there is a reason nobody else did it though. I was hoping someone else did it first and I could learn from them. I'll keep digging.

 

[simp5782]

Thanks, I've read a bunch of the threads on tranny oil and I saw a ton of different options. Looks like everyone mainly keeps whatever is currently in there. I didn't see anyone try 40w though. I'm going to be doing a full fluids/filters change on my new truck. My plan is to use 15w40 but my thought is the thicker the better for Florida's stupid heat. I have to think there is a reason nobody else did it though. I was hoping someone else did it first and I could learn from them. I'll keep digging.

It's best to use transmission fluid if you are doing full swap. It will shift better and stay cooler.

Transynd is the best thing for it

 

[m715mike]

It's best to use transmission fluid if you are doing full swap. It will shift better and stay cooler.

Transynd is the best thing for it

Wes, is this what you are referring to for the transmission in a M923A2?

 

[juanprado]

Wes, is this what you are referring to for the transmission in a M923A2?

View attachment 874281

Interesting as I did not know about the 2021 updated specs.

That does look like the newest stuff for allison's.

 

[simp5782]

You can run TES295 or 668. Doesn't matter

 

[simp5782]

Wes, is this what you are referring to for the transmission in a M923A2?

View attachment 874281

If you are wanting to buy some use BG products ATF. Get it off ebay. Much cheaper. It's good stuff. Most dealers use their products

 

[Steelreaper80]

I just towed an M322 trailer with a 14K tractor on it from Indianapolis to just north of Philadelphia to Cleveland and back to Indianapolis. Needless to say I went through the mountains. There were a LOT of hills that pulled me to the bottom of 2nd gear and 3 that pulled me down to first. 11 MPH at full throttle for 3 plus miles. It took a long time and the truck engine and transmission were getting a workout. But........even on the last and longest first gear pull, the transmission never got above 230 degrees. The engine fan got a workout......but everything went well. I had 15W-40 in my truck when I got it but had it swapped to Dextron VI. It shifts smooth and stays cool.

 

[m715mike]

What is the process for swapping fluids in the transmission, say from 15w40 to Transynd? I assume you can’t get all of the old fluid out even with dropping the pan. Also, I’ve heard that you should not mix the two fluids.

 

[purple_duckk]

I just towed an M322 trailer with a 14K tractor on it from Indianapolis to just north of Philadelphia to Cleveland and back to Indianapolis. Needless to say I went through the mountains. There were a LOT of hills that pulled me to the bottom of 2nd gear and 3 that pulled me down to first. 11 MPH at full throttle for 3 plus miles. It took a long time and the truck engine and transmission were getting a workout. But........even on the last and longest first gear pull, the transmission never got above 230 degrees. The engine fan got a workout......but everything went well. I had 15W-40 in my truck when I got it but had it swapped to Dextron VI. It shifts smooth and stays cool.

I'm pretty sure I've narrowed my issue down to a valve body issue, not overheating. The gauge wasn't giving me the right temp. Adjusting the modulator didn't help and removing the solinoid connections didn't do anything either.

 

[Elijah95]

Thanks, I've read a bunch of the threads on tranny oil and I saw a ton of different options. Looks like everyone mainly keeps whatever is currently in there. I didn't see anyone try 40w though. I'm going to be doing a full fluids/filters change on my new truck. My plan is to use 15w40 but my thought is the thicker the better for Florida's stupid heat. I have to think there is a reason nobody else did it though. I was hoping someone else did it first and I could learn from them. I'll keep digging.

My M923A2 had 15w40 in it, temps stayed low, and worked excellent. I grabbed either delo or delvac that met the Allison spec and away we went. Only catch was I’d let the truck warm up for atleast 15 minutes on the first start of the day during winter, and about 10 minutes in the summer, and drive gingerly manually shifting up until temp came up. Never a problem in 10,000 plus miles


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