Allison Question

froggman180 · 03-28-2007, 10:09 AM

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,
Duane.

TravelswithCharly · 03-29-2007, 07:18 AM

Gearing

This may depend on other factors, but remember the H1 has a 34.5" wheel, compared the 29.5" wheels stock with the allison on the trucks. This makes the effective gear ratio taller, and exactly like the 6 speed, when using 3.73 gears.

What do you have for gearing in the H1?

bnkrupt · 03-29-2007, 08:45 AM

I'm not sure i would be too excited over a Alison for 900-1000. those are the trannys that guys like us abuse for 35,598 miles and switch to ATS or Suncoast... Like Travels said, this tranny will work harder than a stock application due to the larger tires, and you need to be conscious of gear ratio for top end speeds and towing ability. The (stock) transmission is the one of the weakest points of the HD drivetrain, and if you plan on being rough on your H2 without problems, get the suncoast or ATS right off the bat. NOTHING is worse than a smoked tranny on the side of the interstate. and historically, $900 wont buy a "mint" 700R4 + xfer case.... so, food for thought... its a lot easier to do something right the first time... check these guys out! http://www.stallioncustoms.com/h1h2dudico.html

froggman180 · 03-29-2007, 12:21 PM

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.

[b]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

John-Boy 331 · 06-02-2007, 11:50 PM

i had an ally 5 speed in an 02 w/ a 8.1 big block
now i have a 6 speed ally in an 06 w/ a lbz
night and day, love the extra gear running on highways and without doing research on it i feel the 6 has a lower first gear ratio, call a dealer and have them look up the ratio's and ranges in gears, it may just be the motor diff but with that in mind i still feel its more than just hp and torq diff. good luck

**Diesel Nut** · 06-02-2007, 11:59 PM

You should have a 4.92:1 total axle gears when you factor in the 1.92:1 geared hub. Portal axles rock.

With that kind of gearing, and knowing how the military Hummers ran, the extra OD will do you alot of good. Persoanally, if you are going to spend the money on a conversion like this, why not get a new unit from a reputable builder like Suncoast and be done with it, no worries, no questions, you know its good.

Also, with a 5 speed, you can upgrade it to a 6 speed with a kit available from Suncoast that includes a new VB and new TCM.