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trans fluid - M923A2

FXR1969

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Thanks guys!!!! I think!! LOL
Think I'm more confused now than before! was gonna try to jump in this weekend and start changing it but ran out of time
Anyway Hope everyone had a good weekend,
 

Csm Davis

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Here is a link to Allisons current recommentaions which include the MT and HT series. It says that C4 Type fluids are no longer approved for on-highway transmissions (which the MT and HT are).

http://www.allisontransmission.com/docs/default-source/service-documents/st1099s.pdf?sfvrsn=2
NO jjb you are wrong on 2 points, that pdf says the military specifications are still good for military vehicles note number 3, and Allison doesn't list these military vehicles as over the road commercial trucks on their website it list them a specialty vehicles on and off road. Their website list many 15w40 oils as authorized for off road use. So until you can show a Allison document says that a M939 transmission should have something other than 10wt or 15w40 I will completely disagree with your thoughts on the matter.
 

Csm Davis

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Thanks guys!!!! I think!! LOL
Think I'm more confused now than before! was gonna try to jump in this weekend and start changing it but ran out of time
Anyway Hope everyone had a good weekend,
FXR1969 don't just take my word for it but look at what is listed in other treads there have been others that put ATF in their transmission and had to rebuild it, the only way I would recommend changing to the new transyn oil would be if you had it rebuilt and used it from the get go, that way the clutches would only have that oil in them not a mixture.
 

jjb

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NO jjb you are wrong on 2 points, that pdf says the military specifications are still good for military vehicles note number 3, and Allison doesn't list these military vehicles as over the road commercial trucks on their website it list them a specialty vehicles on and off road. Their website list many 15w40 oils as authorized for off road use. So until you can show a Allison document says that a M939 transmission should have something other than 10wt or 15w40 I will completely disagree with your thoughts on the matter.
The HT and MT transmissions are on highway according to Allison. Also, just because it says you can still use the military spec doesn't mean it won't shorten the life of the trans. They list those oils for specific transmissions and it doesn't include the HT or MT.

I am willing to bet the military made Allison support those fluids. There is a reason they don't approve them for any use but the military.
 

Csm Davis

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The HT and MT transmissions are on highway according to Allison. Also, just because it says you can still use the military spec doesn't mean it won't shorten the life of the trans. They list those oils for specific transmissions and it doesn't include the HT or MT.

I am willing to bet the military made Allison support those fluids. There is a reason they don't approve them for any use but the military.
Okay read
http://www.allisontransmission.com/transmissions/vocational-applications/specialty
I will back up what I say
Also your own pdf list the HT and MT as using the military spec read note number 3.
(3) Military specification fluids are approved for use in Military Applications in 3000, 4000, AT, MT, and HT Series products
only,
 
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Coffey1

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I guess we can agree to disagree but the dex is not a good thing if you heavy use these trucks.
I also agree I don't like the heavy 2nd to first shift but it's a truck not a prius. But adjusting shift cable will help with that.
 

wheelspinner

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I worked in heavy transit bus manufacturing for a decade up until 2012. Our customers were very spec driven. Guess what one of the allowed fluids was to be spec'd in a brand new 2012 bus with an Allison transmission was? Yep 15w40.
Here's it's at: they are both allowed from new in the transmissions. You want to use Dexron? Use it. You want to use 15w40? Use it. They both work just fine. And both were allowed from new with a full warranty. There is NO definitive answer where one is just not allowed. Cherry picking info can support any claim. Short answer is do what you want. They are both allowed.

Personally, I use oil because that's what was in it, I have driven the truck THOUSANDS of miles including towing a loaded Deuce over 750 miles in clouding the mountains. Temps never elevated and the truck performed flawlessly.
 

jjb

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I guess we can agree to disagree but the dex is not a good thing if you heavy use these trucks.
I also agree I don't like the heavy 2nd to first shift but it's a truck not a prius. But adjusting shift cable will help with that.
I never said anything about Dex. I was referring to fluids in the TES295 group like castrol transynd. It's not Dex 3.
 

Gunzy

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I have talked with a few trans "Rebuilders" and the consensous from them is if it is "New/Rebuilt" start off with your choice of acceptable fluids(10wt, 15W40, Dexron, etc.), but if the trans is NOT new then it is best to continue using the same fluids that are in it as that is what is absorbed into the clutches and CANNOT be removed from the clutches. They have let me know clearly that a fluid change later in life can possibly lead to failure and to lessen that possibility of that is to just stay with the fluid it started with i.e. engine oil or trans fluid. The previous comment about the boiling points of the fluids is correct in that ATF(Dexron, Type F, ATF+4, etc.) is lower than engine oils(10wt, 15W40) and that is why those oils are used in hard on/off road applications such as our military trucks. This is exactly why I will stay with 10wt in my trans. Now in the end it is your truck and you can do as you wish with it. I hope this is helpful.
 

jjb

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I have talked with a few trans "Rebuilders" and the consensous from them is if it is "New/Rebuilt" start off with your choice of acceptable fluids(10wt, 15W40, Dexron, etc.), but if the trans is NOT new then it is best to continue using the same fluids that are in it as that is what is absorbed into the clutches and CANNOT be removed from the clutches. They have let me know clearly that a fluid change later in life can possibly lead to failure and to lessen that possibility of that is to just stay with the fluid it started with i.e. engine oil or trans fluid. The previous comment about the boiling points of the fluids is correct in that ATF(Dexron, Type F, ATF+4, etc.) is lower than engine oils(10wt, 15W40) and that is why those oils are used in hard on/off road applications such as our military trucks. This is exactly why I will stay with 10wt in my trans. Now in the end it is your truck and you can do as you wish with it. I hope this is helpful.
This is from Allison.
https://youtu.be/lkVN6ZqloSI

All I'm saying is motor oil will work for sure but it will reduce the life of the trans.
 

Gunzy

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This is from Allison.
https://youtu.be/lkVN6ZqloSI

All I'm saying is motor oil will work for sure but it will reduce the life of the trans.
Still not a fair comparison, not a 6X6, not off highway conditions, and not the trans that is in the M939 series truck. You can do what you wish, after all it is your truck. But you really should compare apples to apples and not apples to cats. JMO
 

jjb

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Still not a fair comparison, not a 6X6, not off highway conditions, and not the trans that is in the M939 series truck. You can do what you wish, after all it is your truck. But you really should compare apples to apples and not apples to cats. JMO
As the document I sent earlier reflects this applies to the HT and MT transmissions. The military approved are for just that the military. They required Allison to approve those fluids for logistical reasons not for longevity.
 

Csm Davis

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As the document I sent earlier reflects this applies to the HT and MT transmissions. The military approved are for just that the military. They required Allison to approve those fluids for logistical reasons not for longevity.
No jjb you are wrong again the military did not tell Allison to approve 10wt for logistical reasons. You need to back up your statements with documentation which your pdf on fluid change intervals doesn't. You say that the MT, and HT are HWY transmissions that is also not the full story, yes they can be used in a over the road vehicle, but that is Not what we are discussing. We are talking about the on and off road use of military trucks that originally Allison specified 10wt for and backed with a warranty on 35,000 trucks. The military does give rats behind if they need to get more of a fluid it already gets which at the time in the early 80's I believe would have been dex2, which they had to get for the cucv and humvee.
 

jjb

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Location
Newton/NJ
No jjb you are wrong again the military did not tell Allison to approve 10wt for logistical reasons. You need to back up your statements with documentation which your pdf on fluid change intervals doesn't. You say that the MT, and HT are HWY transmissions that is also not the full story, yes they can be used in a over the road vehicle, but that is Not what we are discussing. We are talking about the on and off road use of military trucks that originally Allison specified 10wt for and backed with a warranty on 35,000 trucks. The military does give rats behind if they need to get more of a fluid it already gets which at the time in the early 80's I believe would have been dex2, which they had to get for the cucv and humvee.
Think about this. Allison says that those fluids are now only approved for military applications. If your beloved motor oil was so good for the trans why would it not be approved for all users?

Seems pretty obvious to me.
 

Csm Davis

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Think about this. Allison says that those fluids are now only approved for military applications. If your beloved motor oil was so good for the trans why would it not be approved for all users?

Seems pretty obvious to me.
Because you have on blinders and are wrong they are also for off road trucks get your facts straight the only place that they are not using them is over the road.
 
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jjb

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Newton/NJ
Because you have on blinders and are wrong they are also for off road trucks get you facts straight the only place that they are not using them is over the road.
Believe want you want. I've talked directly to people at Allison who are the experts. I stand behind my information.

Call and ask yourself. It's a slow painful process to get to the correct people.

I'm done with this thread.
 

Csm Davis

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Believe want you want. I've talked directly to people at Allison who are the experts. I stand behind my information.

Call and ask yourself. It's a slow painful process to get to the correct people.

I'm done with this thread.
Please by all means change yours out and tell us how that goes. I wish you all the luck with that but I am going to keep using what came in mine and I use my trucks. Like this yesterday.
 

162tcat

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No reason to argue. I run dex 3 in my 931a1 and 15-40 delo in my m923a2. Both work hard and have no problems. Probably 20k miles between the 2 of them. Dex 3 shifts smoother and 15-40 shifts hard but both are fine. Run what you want and have fun driving a big ass truck, no reason to get personal on this.
 
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