Allison MT643 for 1,500+ hp??

JQmile

JQmile

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Nov 19, 2006
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Some of 'em came behind Cummins, right? I talked to a shop today about them, huge shafts, four gears, lockup, can be controlled manually.....think one would work without breaking in a mega-hp street truck? Oh yeah, and only $2K for a rebuild. They also said they weigh about 500 pounds, which is a good amount, but maybe not for ultimate reliability.
 
the at545 and mt643 are decent trannies, I don't know about for that much power though. I know a drag truck up here used a mt643 and had to rebuild it often. it was behind a 1000ish HP 2stroke detroit though.
 
1-5-3-6-2-4 said:
the at545 and mt643 are decent trannies, I don't know about for that much power though. I know a drag truck up here used a mt643 and had to rebuild it often. it was behind a 1000ish HP 2stroke detroit though.
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In what though?

Weight could be a big factor in the life span...if you're talking 1000hp truck engines pushing 10-12K lb semi's, then in our trucks at say 6-7K lbs (or less) they might hold up to a tone of abuse?

Chris
 
I used to work at an allison distributor and have thought about this, the problem I see is the size of the the dang thing.They are much larger than a Allison 1k or a 47/48.
 
Signature600 said:
In what though?

Weight could be a big factor in the life span...if you're talking 1000hp truck engines pushing 10-12K lb semi's, then in our trucks at say 6-7K lbs (or less) they might hold up to a tone of abuse?

Chris
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that is entirely true. it was in a stripped out bigrig race truck. I say go for it. Cryo treat the shafts and gearsets. and let 'er buck.


the mt600s aren't that much bigger than the 1k/2k units. they are larger, but not gargantuan. the ht740 750s are fully 3 times bigger though.
 
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skidooman said:
I used to work at an allison distributor and have thought about this, the problem I see is the size of the the dang thing.They are much larger than a Allison 1k or a 47/48.
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I have 3" body lift on my truck and I think that is plenty of room for any of those Allison who goes behind 5.9 cummins.

I have an AT545 seating in the back of my shop that I wanted to try a couple years ago and that was not even a challenge to fit in there !

My NV5600 is the same or bigger than an AT545 and I have lot's of room around the dam thing still !

Just my $.02
 
well you are going to have to change out your flywheel housing for the big thick one !!!
 
Anyone know if any of these were available with overdrive? Im sure some were but how do you identify them?
 
Knoberman said:
Anyone know if any of these were available with overdrive? Im sure some were but how do you identify them?
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As far as I know, no they weren't ever built with an overdrive. I thought about using one once, but they are big and heavy, and do shift slow. I'm sure someone could get them to shift faster, but I heard they won't shift real fast just because of how they're designed. Here is one next to a standard sized pressure washer for an example.

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I had a MT40 in my truck it was a 6 speed that was the hardest hitting trany I had it broke almost all of the rear springs from slamming sohard.i weight was almost 400lb was cast iron.Now I'm putting in a 06 allison 6sp.can't wait.Tired of shifting the 10sp.
 
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