Allison Transmission in M923A1

jstier · Nov 11, 2011

My M923A1 seems to shift to fast from 2nd to 3rd. All the other gears hold in longer. Just was Wondering if this is Normal and or is there any way to change shift points?

BKubu · Nov 11, 2011

It IS and it IS NOT normal. I say it IS normal because I have had other M939 series trucks that shifted like this. I say it IS NOT normal because they are not supposed to shift like that. You should take it to an Allison dealer to have them check the shift points. You could also have a bad shift modulator cable, among other things. Changing the shift modulator cable is fairly straight forward; setting the shift points, if you don't know what you are doing, is not.

Good luck.

jstier · Nov 11, 2011

Bruce,
Thanks for the info. I was planning on calling Allison dealer to see what they would charge to flush the 10w oil out and change it over to DexIII, so I'll add this to the list.

Thanks

BKubu · Nov 11, 2011

Jeff, I can't rememer what the Allison dealer near me charged to service the transmission (fluid flush and filter) and check the shift points, but I recall thinking that it was not as much as I thought it would be. If you want to truly rid your truck of the 10W oil, you will have to change the fluid multiple times since you can't actually get all of the old fluid out when you drain it. I just had my M923 serviced for the same reason and I know I'll have to go back in about 500 miles or so.

jstier · Nov 11, 2011

I spoke with local Allison shop and was quoted $400 for flush, Fill and Filter and $100-200 to adjust shift points. Im fine with the price on adjusting shift points, But flush and fill seems high to me. I can change it myself a bunch for that cost, but then I'd have to live with shift points where they are.

indy4x4fab · Nov 11, 2011

have allison adjust the shift points then change the fiuld your self, buy your filters while your there. I'm a big fan of buying o.e.m. parts, they fit better then the made in china crap.

jstier · Nov 11, 2011

indy4x4fab said:
have allison adjust the shift points then change the fiuld your self, buy your filters while your there. I'm a big fan of buying o.e.m. parts, they fit better then the made in china crap.

Indy,
Not knowing much about the allison, They adjust shift point externally? Main reason I wanted them to flush was because of Torque converter. I figured Id have to change it a million times to get all the 10w out

BKubu said:
I just had my M923 serviced for the same reason and I know I'll have to go back in about 500 miles or so.

Bruce,
You have to go back in 500miles, Is the because they couldn't get all the 10w flushed? How many times are they going to have to fush it?

indy4x4fab · Nov 11, 2011

I think those allisons where computer controlled if I'm not mistaken?

BKubu · Nov 11, 2011

jstier said:
Indy,
Not knowing much about the allison, They adjust shift point externally? Main reason I wanted them to flush was because of Torque converter. I figured Id have to change it a million times to get all the 10w out

Bruce,
You have to go back in 500miles, Is the because they couldn't get all the 10w flushed? How many times are they going to have to fush it?

Yes, they could not get it all out. There is so much fluid in the torque convertor that they really only remove 80% or so of the fluid.

jstier · Nov 11, 2011

indy4x4fab said:
I think those allisons where computer controlled if I'm not mistaken?

Not according to the service advisor @ allison dealer i spoke too. He even stated wow we haven't adjusted a non computer controlled transmission for awhile. Didn't give me the warm fuzzies, but atleast they have done it, that's more than i can say.

mktopside · Nov 11, 2011

jstier said:
Not according to the service advisor @ allison dealer i spoke too. He even stated wow we haven't adjusted a non computer controlled transmission for awhile. Didn't give me the warm fuzzies, but atleast they have done it, that's more than i can say.

When I asked the one around here about adjusting the shift points on my AT1545, they quoted me $900 to pull it out and put it on the machine. I was given the impression that there are a few half measures that were possibities before it got to that point. There is something else they can adjust, but I can't remember what it is.

BKubu · Nov 11, 2011

mktopside said:
When I asked the one around here about adjusting the shift points on my AT1545, they quoted me $900 to pull it out and put it on the machine. I was given the impression that there are a few half measures that were possibities before it got to that point. There is something else they can adjust, but I can't remember what it is.

You should not have to pull a transmission to set the shift points, unless I missed something in this thread. They should be able to adjust the shift points with the transmission in the truck.

jstier · Nov 12, 2011

BKubu said:
You should not have to pull a transmission to set the shift points, unless I missed something in this thread. They should be able to adjust the shift points with the transmission in the truck.

I agree, other wise they wouldn't have quoted me 100 - 200 for it. I am going to call them Monday and ask If I can watch Tech do the job. It's probably about a 10% chance they will let me, but if they do I'll ask lots of questions and take pics so I can post on here. I did find a TM about the transmission and it taked about different spring colors but it didn't go itto any details about how to do it.

jstier · Nov 12, 2011

Found the recomended shift points in the TM. Here is a copy. Im going to check it tomorrow, then check Modulator and cable adjustments per TM. I'll Post what I find tomorrow night.

engineer233 · Nov 12, 2011

I am a new M923 owner so I have to ask , what is so bad about the 10w in the tranny and why is the dextron so much better ?

BKubu · Nov 12, 2011

jstier said:
I agree, other wise they wouldn't have quoted me 100 - 200 for it. I am going to call them Monday and ask If I can watch Tech do the job. It's probably about a 10% chance they will let me, but if they do I'll ask lots of questions and take pics so I can post on here. I did find a TM about the transmission and it taked about different spring colors but it didn't go itto any details about how to do it.

The different spring colors correspond to how hard or soft the transmission will shift. I had a truck that was downshifting hard from 2nd to 1st and it was not normal, so they swapped out the spring with another and it corrected the problem.

jstier · Nov 12, 2011

engineer233 said:
I am a new M923 owner so I have to ask , what is so bad about the 10w in the tranny and why is the dextron so much better ?

Do a search to find out all the info, its has been posted on a bunch, but the short story is Allison doesn't recomend it. The military does use it and it works, But Dex III is so much better.

jstier · Nov 12, 2011

BKubu said:
The different spring colors correspond to how hard or soft the transmission will shift. I had a truck that was downshifting hard from 2nd to 1st and it was not normal, so they swapped out the spring with another and it corrected the problem.

Thanks Bruce,
I'm learning a little at a time, but thats still learning.

jstier · Nov 13, 2011

today I started with "automatic shift test." (See above post for Pic) mine weren't quite to spec so I the printed out of TM "Transmission Modulator and cable Maintance" I found that mine was a little out of adhustment. So I followed the step and got it set. took her out and reran "automatic shift test." and Everything is to specs now. Thanks Bruce for clueing me in on the Modulator.

indy4x4fab · Nov 14, 2011

glad to hear you got the old girl up and running back to spec.

Allison Transmission in M923A1

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