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Allison Question

2771 Views 5 Replies 5 Participants Last post by  Diesel Nut
I am planning a transmission swap in my 1998 H1. The donor transmission is going to be an Allison.
I was wondering from anyone who has experience towing how is the 6 speed compared to the 5 speed?

Right now I am having a hard time finding a 6 speed, but I have found some 5 speeds for $900 to $1000. I know if I can find a used 6 speed it would be at least double.

Would that extra overdrive on the 6 speed benifit my truck?
Would the extra money that I would pay be worth it?

My hummer is over 10,000 lbs and has very poor aerodynamics. But I guess anyone towing a large 5th wheel is also heavy with limited aerodynamics.
Thanks for any help,
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I dont know the gearing or any of the specifics.
Remember the stock H1 for 2006 comes with a 5 speed Allison stock, my truck is a 1998 with a 4L80E.
The company that is going to do the conversion for my H1 does them for a small unit in the military with huge success.
I just have to supply him with a solid transmission. He does the 5 speed and has not done a 6 speed before. But he states that it would be the same type of install, he would have to flash the ECU a little differently is all.

The big question is 5 speed or 6 speed.

Using a 6 speed is the big unknow because I cant find anyone who has done it. My truck has limiting factors that might make the 6th speed useless. Here they are: The truck wieghs over 10,000 lbs and it is extremely NON AERODYNAMIC. I usually dont drive any faster than 60 to 65 and the average would be more like 60
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