Allison AT1545 failures

Has your 1545 failed (any reason, not just R/4)?


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    9

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rustystud

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The Allison AT540 series transmission is a great transmission. It has been working in trucks since 1970 now. The main reason they fail is lack of proper maintenance. This is the main reason most equipment fails. Since they are such a good transmission and are very strong, most people tend to overlook them when maintenance comes along. The filters need to be replaced on a "regular" basis. Not just when you remember to do it. Little bits of crud and metal particles get through a old filter and cause havoc to finely machined parts like the pump gears. When the pump goes it usually takes out the whole transmission. All this being said, most people who get a M35A3 had nothing to do with the lack of proper maintenance. You just "inherited" the problem !
So for those buying a M35A3, I would say the first thing to do before any other (except brakes) is replace the filter and fluid in the transmission.
It can save you a ton of grief down the road.
 
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Redneck of Enon

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I agree with rusty ....the first thing I did to my M35A3 was change the trans fluid and both trans filters.... i had to get used to how the transmission shifts , if I don't hold the pedal to the floor when its time for it to shift into 4th gear then the transmission jerks and makes a noise that doesn't sound good so I just put the pedal to the metal....and roll on....long live my M35A3 !
 

mann650

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That was one of the first things I did as well. The oil that came out looked good, smelled fine, tasted great. I did not see any signs of trouble, no aluminum, no burnt smell but I do wonder how many transmissions have survived vs died. The most noticeable change has been the transmissions willingness to get out of 1st on a cold morning, it used to take forever to heat up and start shifting well. looks like we are 50/50 on my entirely unscientific poll, about what I expected. keep the votes coming.
 

rustystud

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That was one of the first things I did as well. The oil that came out looked good, smelled fine, tasted great. I did not see any signs of trouble, no aluminum, no burnt smell but I do wonder how many transmissions have survived vs died. The most noticeable change has been the transmissions willingness to get out of 1st on a cold morning, it used to take forever to heat up and start shifting well. looks like we are 50/50 on my entirely unscientific poll, about what I expected. keep the votes coming.
Oil changes on an automatic transmission help the gunk that gets trapped in the valve body to come out. Since the oil level usually comes to the bottom of the valve body, the gunk doesn't have gravity to help it drain away. Once the oil level drops, it drags out the oil in the valve body and with it the crud that gets stuck in all those little nooks and crannies. Also when the new oil comes busting in the valve body, it loosens the crud and it gets dropped into the pan and the filter gets it trapped.
 

URSATDX

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9k showing on the odo and it still works fine.

15w40 MO looks clean.

Any thoughts on what brand of 15w40 would be a good choice when I do the fluid and filter(s) changes on the trans.

15w40 specs/additive packages have changed a lot over the past 20 years or so.

Very hesitant to swap to ATF at this point.

Thanks to all.

God Bless America
 

SteelNinja

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A friend has an A3 Im supposed to go look at .. So Im interested in the Trans ( as a weak link ) , Arent some lock up converter and some not? I used to build automatics years ago - 350 -400 - 727- 518-618 , etc I sure wouldnt think motor oil is the thing for a transmission.. I good synthetic yes - but oil? hummm I would think the transmission fluid ( ATF ) would do a better job a cooling and cleaning ..
Ive never messed with a Allison but I dont think it could be too hard to fix... Is there a way to tell which trans you have by looking or does it have to be driven to tell??
 

Floridianson

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Would seem if you switch to ATF as long as you do not over heat the oil / the transmission then all might be good. Engine oil was approved buy a fluid engineer that I posted here. There were some problems when some switched to ATF in the bigger machines.
The engine oil kept the transmission running cooler. When you have heavy weights in the truck, slow ground speed and high rpm it all most has to get hot. Watch your trans. temp gages while off road and going slow.
 

russojap

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How much would the A3 transmission cost to rebuild?

Also, I can't speak for the truck transmission, but my 1999 Camry had 199k on it when I got it. The tranny fluid was dark and sparkling with metallic looking particles. I didn't dare chang it and never have, it now has almost 319k miles.

You probably already know this but sometimes the old fluid is the only thing keeping the trans working. I've Seen and heard about too many failures after fluid changes.After a long time between changes that is.

I never change the oil either! [thumbzup]

Haha just kidding about the oil. :lol:

Screenshot_20190918-001112~2.png

https://youtu.be/EJkepVMTfmQ
 
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rustystud

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Woodinville, Washington
9k showing on the odo and it still works fine.

15w40 MO looks clean.

Any thoughts on what brand of 15w40 would be a good choice when I do the fluid and filter(s) changes on the trans.

15w40 specs/additive packages have changed a lot over the past 20 years or so.

Very hesitant to swap to ATF at this point.

Thanks to all.

God Bless America
The Allison was never made from the manufacture to run on engine oil. That was a "military" decision. A good Dexron III or better oil is so far superior to engine oil that it is not funny ! A transmission oil must be a "lubricating oil" and a "hydraulic oil" at the same time. Engine oil is just a lubricating oil period. (Except in the IHC engine used in Fords, but that is a different story and they require stringent oil requirements and oil drainings.)
You would do well to totally drain the transmission and replace the filter and refill with Dexron. There has been so much written on this, just do a little research. Go to Allison's website and see what they recommend for the transmission "they" designed and built.
 

Floridianson

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9k showing on the odo and it still works fine.

15w40 MO looks clean.

Any thoughts on what brand of 15w40 would be a good choice when I do the fluid and filter(s) changes on the trans.

15w40 specs/additive packages have changed a lot over the past 20 years or so.

Very hesitant to swap to ATF at this point.

Thanks to all.

God Bless America
The old saying if it is not broken don't fix it. I never had a problem with my A3. My Allison in my 915A2 has engine oil and no problems so far and thousands of miles. After talking to the Allison fluid engineer that ok engine oil in our trucks back in the day I left mine alone. He also said the transmissions never showed any kind of failure because of the engine oil. I will run the engine oil till or if the transmission fails then switch fluid on rebuild. I much rather not take one chance by switching and have to spend thousands of dollars when the transmission is working.
 
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mann650

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Floridianson - I'm curious, did the fluid engineer give any reasoning to why the transmission would run cooler with a thicker oil? I've always assumed that a thicker oil would allow components to heat up more, but that was always my assumption, I don't have any basis behind that.
 

Sgt Jiggins

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I’d like to go right back in with the 1545 so that I don’t have to adapt something else. Hoping someone on here has one kicking around.
 

rustystud

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So many differing opinions.
ATF vs MO.
I'd love to replace the oil with a modern high quality ATF.
vs
If it works don't fix it.

https://www.allisontransmission.com/parts-service/approved-fluids/off-highway-fluids
Actually there's not that many opinions here. There's just a few that feel the military can do no wrong so why change it. Most believe the "manufacture" has the best advice for their product. After all "they" designed it and built it.
I worked at a "Detroit Diesel Allison" shop in the transmission department and actually worked with Allison engineers at the transit department. Our transit agency was one of the first in the nation to go to the "Hybrid Transmission" . So we had engineers crawling out our butts back then ! No one ever told me that running engine oil was a good thing.
I also worked with a German engineer from "ZF" for a year. We where having trouble keeping the transmissions going past 30,000 miles then. Great guy. After living here for a year he brought his wife and children over and became a US citizen . Turns out we had gearing problems. The bus was to heavy and the gearing to high (to be able to run on the freeways) . The transmissions torque converter was working too hard building up to much heat, which took out clutches. Instead of going to a 6 speed transmission, they opted to install larger cooling radiators. That's government for you.
 
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Floridianson

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Just to be clear I would never say engine oil peforms better than ATF on road in the Allison. My only fear is I will be the one that with the switch has a problem. I think I will just stay with the engine oil for now in the 915A2. If it has a problem in my life time then since my motor is computer controlled switch out from the governor controlled Allison four speed to a computer controlled newer one. Sold the Deuce A3 so that takes care of that truck. As always your truck so do what you think is best. Was interesting reading that for off road Allison has engine oil listed thanks URSATDX. https://www.allisontransmission.com/parts-service/approved-fluids/off-highway-fluids
 
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