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M109a4 /a3: Reducing rpms, gaining speed / tranny / gearing solution & crowd sourcin

m-35tom

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eldersburg maryland
that is what i am thinking, i ran 70 for 5 hrs a few mths ago. high idle on my 9.0 is 3000 rpm and it is rated that for continuous use, have never run it up that fast yet.
 

rustystud

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The 5 tons used the MT654, this is an obsolete trans with only limited support by allison and costly parts.

As long as the AT1545 locks in 3 and 4 it would operate the same.


The AT1545 is 27.2" long 302 lbs SAE 3

The MT643 is 30.4" long 478 lbs SAE 2

The MT653 is the long and heavy one, 36.2" long 602 lbs
The only difference between the MT653 and the MT643 is the low reverse clutch pack as the 653 is a 5 speed and the 643 is a 4 speed. The clutch adds to the extra length. Both can come with a SAE 2 or 3 bellhousing . It is NOT a discontinued transmission. Both have lock-up torque converters and both are a 1:1 ratio at top speed. I have rebuilt plenty of these transmissions and many trucks and busses still use them. The AT, MT, and HT series transmissions are decades old but still used today. In fact our new wrecker came with a HT754DR. DR stands for "deep ratio" and the CR stands for "close ratio" . This is for the first gear. So a MT653DR is a 5 speed with a really low first gear.
 

quickfarms

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Orange Junction, CA
Oh darn, yeah I didn't realize that. Man o' man, Kalifornia.... I'm sorry.
It can actually be an nice advantage when driving on the freeway in an older vehicle that can at least do 55. I have found my self in the right lane with an 80,000 lb battering ram protecting my six from the crazy four wheelers or weekend warriors. I had a bob tail jump in front of me to protect me from the toy hauler that tried to pass on the right and lost it in the dirt.
 

rustystud

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Woodinville, Washington
002.jpg I decided to post this picture showing a Spicer 3053 manual
transmission and a Allison MT654CR automatic transmission. You can see that the Allison is way to long and big to fit behind our multifuel engines. Even if you went with the 4 speed MT643CR it would be to long and big !
I was going to use the MT654CR in one of my Tractor trucks but decided to stay with the 5 speed manual that is already in it.
 

rustystud

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Woodinville, Washington
As long as the AT1545 locks in 3 and 4 it would operate the same.


I forgot to mention that the AT500 series (which the AT1545 belongs to) transmission does not have a lock-up torque converter, nor does any of the gears lock-up like the larger transmissions do. Basically the AT500 transmission is just a TH400 on steroids. In fact the direct and fourth gears clutches are the same as the TH400 direct and forward clutches. We used to use AT500 series clutches in the TH400 to help beef it up as the clutches in the AT500 where made from a asbestos type of material which could handle the heat better.
 

rustystud

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Woodinville, Washington
I love my AT545. Don't really care about that haters. :D
Who said anything about hating the AT545 ? I love those Allisons ! I wouldn't have worked for them if I didn't like them. I would still love to put one in my 1 Ton truck someday. I just cannot fit that MT654CR into my deuce without removing a lot of stuff and pushing the transfer-case back about 15" . Remember my specialty was automatic transmission repair, because I love them ! Actually my shop specialty was "gear repair" I just loved working on the automatics better.
 
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