Allison 1545 Automatic Transmission Specs

Redneck of Enon

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I am planning on doing the MO to ATF conversion on my Allison 1545. I will introduce the ATF thru the check/fill tube. In order to insure a complete and thorough flush what would be the best point to disconnect the flow circuit so that the entire trans and cooling system are flushed. I’m assuming the ideal disconnect would be at the return line at the transmission. Thoughts? If this seems to be the best location, I would need to confirm the direction of flow of the MO/ATF in the system. I am ASSuming that the fluid flows from the trans to the top of the radiator out the lower radiator to the trans cooler (top) and from the cooler back to trans. If this is the correct direction of flow then I will proceed to flush until the fluid at the trans return line is all ATF and no MO. I’d then drop the pan, replace filter and gasket. Replace the inline spin on filter, run and adjust fluid level.

Suggestions on ATF types?

Any thoughts from the troops?

Much appreciated.

God Bless our Great Country!
how did it go ?
 

Sgt Jiggins

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Has no one found a alternative transmission for the A3 (maybe one with an overdrive)
Had I not had success with my 1545 rebuild (which cost me north of $10k for a variety of reasons, some of which were unrelated to the 1545 itself), I had plans in the works to install an MT643.

The mount to the bell housing will meet up. You will likely need to move the transfer case "back" in the frame rails a bit. Which means new/modified drive shafts and control levers. Not a huge deal.

And the transmission fluid cooler will need to be upgraded. Because of the required capacities. And the stock hose sizes themselves being too small for the required flow rate of the larger MT643 transmission.

But.

It is all possible and something with a bit of precedent: apparently the Canadian variant of the M3xA3 trucks came with the MT643. Granted they had a different powerplant- not a Cummins but a Detroit I believe.

If you run into a brick wall with your 1545, which I very nearly did, you do have options.

Bonus: the MT643 is a far more robust transmission and will almost certainly outlast the truck, us, and maybe the sun.
 

HDN

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Had I not had success with my 1545 rebuild (which cost me north of $10k for a variety of reasons, some of which were unrelated to the 1545 itself), I had plans in the works to install an MT643.
What was the cost of the rebuild alone? I've seen around $2000 mentioned here a few times, with most of it consisting of replacing broken pistons and seals with 4L80E ones by an Allison shop. I'm hoping I won't need one for some time, assuming that the Military Mail Terminal it was assigned to didn't go crazy with the truck!
 

Sgt Jiggins

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I'd say I was in for ~$3500. It could've been had for less, sure. That's what I wound up with because I knew they could do the job and I was exhausted from fooling with it for more than a year.

There are folks on here (RustyStud, ahem) who're veritable gurus. Make certain to do your homework before going down that road. Removing&reinstalling these transmissions isn't simple. Well, it is. But it's Heavy. The guy who put mine in wound up with a forklift to get it in. I kept clear, watched, and smiled that I wasn't doing it myself.
 

Budrow

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Yakutat, Alaska
Hello all, you can add me to the list of smoked transmissions. I'm in the process of replacing my 1545 with a 545. Does anyone know what the Cat part number for the flywheel that needs to be replaced is. Been looking in TM's can't find it.
 

HDN

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Hello all, you can add me to the list of smoked transmissions. I'm in the process of replacing my 1545 with a 545. Does anyone know what the Cat part number for the flywheel that needs to be replaced is. Been looking in TM's can't find it.
Per PDF page 729 of TM9-2320-386-24-1-2:

1652823508116.png

The part number is 23045001. I found the first reference to this on PDF page 352 of the same book under the Materials/Parts list for TRANSMISSION (IN-VEHICLE) REPLACEMENT for replacing the AT1545P with an AT545.

It appears that it was common on school buses, but I've only found one source selling it for around $500, which seems absurd to me. It would probably be cheaper to get one machined if you could get the specs for it. Or maybe you'll be able to find one for the right price!

Do you know what's wrong with your transmission? I think in most cases you should be able to have it rebuilt since it has the same core as an AT545.
 

Budrow

Member
14
27
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Location
Yakutat, Alaska
Per PDF page 729 of TM9-2320-386-24-1-2:

View attachment 867999

The part number is 23045001. I found the first reference to this on PDF page 352 of the same book under the Materials/Parts list for TRANSMISSION (IN-VEHICLE) REPLACEMENT for replacing the AT1545P with an AT545.

It appears that it was common on school buses, but I've only found one source selling it for around $500, which seems absurd to me. It would probably be cheaper to get one machined if you could get the specs for it. Or maybe you'll be able to find one for the right price!

Do you know what's wrong with your transmission? I think in most cases you should be able to have it rebuilt since it has the same core as an AT545.
Thanks for the reply, and the help. That is spendy! The trans always had a hard time shifting into 4th gear, and finally started slipping when in reverse, just like everybody else that's had problems with these. The fluid was black, I'm sure its tired. The 15-40 was changed out 6 yrs ago. Its cheaper for me to go with the 545 so far. Hopefully I can find the flywheel at a good price. I mainly run my truck on the beach in AK, so don't need a locking torque converter. Thanks again for the info.
 
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Budrow

Member
14
27
13
Location
Yakutat, Alaska
Per PDF page 729 of TM9-2320-386-24-1-2:

View attachment 867999

The part number is 23045001. I found the first reference to this on PDF page 352 of the same book under the Materials/Parts list for TRANSMISSION (IN-VEHICLE) REPLACEMENT for replacing the AT1545P with an AT545.

It appears that it was common on school buses, but I've only found one source selling it for around $500, which seems absurd to me. It would probably be cheaper to get one machined if you could get the specs for it. Or maybe you'll be able to find one for the right price!

Do you know what's wrong with your transmission? I think in most cases you should be able to have it rebuilt since it has the same core as an AT545.
I don't know, I need to do some more research, but that looks like the adapter ring the trans bolts to ? I was told I need to change the actual flywheel/ring gear, along with changing out the flex plate, with two different ones. I'm still trying to figure it out. Thanks again!
 

HDN

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Finger Lakes Region, NY
I don't know, I need to do some more research, but that looks like the adapter ring the trans bolts to ? I was told I need to change the actual flywheel/ring gear, along with changing out the flex plate, with two different ones. I'm still trying to figure it out. Thanks again!
I read your question a second time and realized that I found you an adapter plate and not a flywheel. According to the TM a flywheel swap isn't necessary, just the adapter plate:

1652831154911.png
 

HDN

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Location
Finger Lakes Region, NY
Great info thanks again! Ill let you know how it works out.
You're welcome - I hope your project works out!

Seeing that you're new here, I encourage you to introduce yourself in Member's Rides or the "Requirements For New Members" boards and share some pictures of your truck :)
 

Budrow

Member
14
27
13
Location
Yakutat, Alaska
You're welcome - I hope your project works out!

Seeing that you're new here, I encourage you to introduce yourself in Member's Rides or the "Requirements For New Members" boards and share some pictures of your truck :)A6F53B1D-1BC4-4694-9768-C0D8596C6FEC.jpeg767F8F8E-923B-49B2-BC35-8B8812B4F411.jpegDD27208C-0E88-4DAA-9B15-6177D06B03DF.jpeg8FD14765-7685-46A3-A923-7062C35193C9.jpeg
Ill check it out, I'm not to savvy negotiating my way around forum
You're welcome - I hope your project works out!

Seeing that you're new here, I encourage you to introduce yourself in Member's Rides or the "Requirements For New Members" boards and share some pictures of your truck :)
Roger that, will do. Would you happen to have a link for
TM9-2320-386-24p. And TM9-2320-386-24-1-1. I tried jatonka but kept getting a 404 error.
 
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HDN

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Would you happen to have a link for
TM9-2320-386-24p. And TM9-2320-386-24-1-1. I tried jatonka but kept getting a 404 error.
That's a nice-looking truck! It looks like it earns its keep! Keep in mind that the AT545/AT1545 are designed to handle a GCVW of about 24000 lbs. Even when the truck is loaded to the data plate weight and towing 6000 lbs also per data plate, the transmission will be overloaded.

I got most of my TMs from Jatonka's, but got the rest of them here. You can find all M35A3 TMs and M35A2 reference TMs in this post here: https://www.steelsoldiers.com/threads/tms-for-the-deuce.77607/

Note that any parts on the M35A3 unchanged from the M35A2 will be referenced in the M35A2 TMs. Anything on the M35A3 that's not on the M35A2 will be in the M35A3 TMs. The M35A3 TMs are new enough to be searchable with your favorite PDF reader typically by using Ctrl+F.

I even found an Allison AT1545 and AT545 service manual in case you ever want to try and rebuild your original transmission: https://www.steelsoldiers.com/threads/m35a3-trucks-allison-at545-1545-service-manual.200257/
 

Budrow

Member
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27
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Location
Yakutat, Alaska
Ill check it out, I'm not to savvy negotiating my way around forum

Roger that, will do. Would you happen to have a link for
TM9-2320-386-24p. And TM9-2320-386-24-1-1. I tried jatonka but kept getting a 404 error.
It
That's a nice-looking truck! It looks like it earns its keep! Keep in mind that the AT545/AT1545 are designed to handle a GCVW of about 24000 lbs. Even when the truck is loaded to the data plate weight and towing 6000 lbs also per data plate, the transmission will be overloaded.

I got most of my TMs from Jatonka's, but got the rest of them here. You can find all M35A3 TMs and M35A2 reference TMs in this post here: https://www.steelsoldiers.com/threads/tms-for-the-deuce.77607/

Note that any parts on the M35A3 unchanged from the M35A2 will be referenced in the M35A2 TMs. Anything on the M35A3 that's not on the M35A2 will be in the M35A3 TMs. The M35A3 TMs are new enough to be searchable with your favorite PDF reader typically by using Ctrl+F.

I even found an Allison AT1545 and AT545 service manual in case you ever want to try and rebuild your original transmission: https://www.steelsoldiers.com/threads/m35a3-trucks-allison-at545-1545-service-manual.200257/
Ok. Great I appreciate the info. Hopefully have this thing running again soon. Cheers!
 
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