Is it possible to install a 4l80 transmission in my 07 H-3 with the 3.7 engine?

[Tbear]

What do I need to do to install a bigger transmission into my H-3 with the 3.7 engine? I am almost thinking about a complete engine and transmission swap as 6.0 engines with the 4l80 transmission are not expensive anymore where I live, but what all would I need to do for the swap?

 

[cgalpha08]

4l80 is physically bigger, bell housing is bigger and it's longer over all by like an inch or so, and heavier. The 4l60e also has a 27 spline output shaft and the 4l80 has a 32 spline. So you'll have to figure out how to mate it to the factory transfer case or go with an aftermarket transfer case.

I'm sure others will agree. If you're going this deep, just swap the 3.7 with a ls v8.
To mate a ls with the stock transmission youll need a new wiring harness. All of the accessory drive stuff, etc.

Remember the h3 is a pass drop front axle, so the transfer case is passenger drop. That makes is difficult to do complete drive train swaps.

Either have to do engine/trans/tcase and an sas to swap the front around. Or engine/w/stock trans and keep the front axle as is.

It just comes down to how many different puzzles do you want to solve

 

[CaseyS]

What problem are you trying to solve with a "bigger" transmission. 4l60 and 4l80 transmissions are dinosaurs.

 

[Tbear]

4l80 is physically bigger, bell housing is bigger and it's longer over all by like an inch or so, and heavier. The 4l60e also has a 27 spline output shaft and the 4l80 has a 32 spline. So you'll have to figure out how to mate it to the factory transfer case or go with an aftermarket transfer case.

I'm sure others will agree. If you're going this deep, just swap the 3.7 with a ls v8.
To mate a ls with the stock transmission youll need a new wiring harness. All of the accessory drive stuff, etc.

Remember the h3 is a pass drop front axle, so the transfer case is passenger drop. That makes is difficult to do complete drive train swaps.

Either have to do engine/trans/tcase and an sas to swap the front around. Or engine/w/stock trans and keep the front axle as is.

It just comes down to how many different puzzles do you want to solve

Thanks for your reply. I understand that you can beef up the 4l65E transmission and it should be able to handle the power of a mild LS engine. I tried to get a alpha when I bought my H-3 but there just wasn’t any available at that time at a reasonable cost. I’m a retired heavy equipment mechanic and I have done some pretty interesting swaps over the years. I suppose I should be looking for a later version of the LS and modifying it for my use. I was considering putting the LS in my 2014 caddie srx, but it is actually pretty quick as it is and the Hummer would benefit greatly from the swap. Thanks again.

 

[cgalpha08]

Thanks for your reply. I understand that you can beef up the 4l65E transmission and it should be able to handle the power of a mild LS engine. I tried to get a alpha when I bought my H-3 but there just wasn’t any available at that time at a reasonable cost. I’m a retired heavy equipment mechanic and I have done some pretty interesting swaps over the years. I suppose I should be looking for a later version of the LS and modifying it for my use. I was considering putting the LS in my 2014 caddie srx, but it is actually pretty quick as it is and the Hummer would benefit greatly from the swap. Thanks again.

No problem. Yea it's just comes down to, which headache do you want to try and fix/deal with. Anything is possible with the right amount of $ haha

 

[Doc Olds]

A 4L60E can be built for 1,000 HP and has in drag applications, that is significantly more than a mild LS motor. It is all a matter of how much do you want to spend to abuse it.

The best way is to sell your I5 and buy an Alpha, then mod that.

 

[atvspeed4]

There is a company that makes a conversion kit for the H2 that allows install of 4l80. Kit for H2 It has a 27 spline output shaft and harness I believe. You would need to make a new transmission crossmember like we needed to do for our 6l90 swap along with transfercase adapter since h3 is 5 bolt vs normal gm fullsize is 6 bolt. The other issue is the torsionbar crossmember clearance I am not sure how much room you would have with the transmission being longer and the factory t case.

 

[06 H3]

Another issue with the 4l80 is that the 1st gear ratio is higher than the 4l60E. So it will make the 3.7L feel even slower. Overdrive is lower so that might be nicer at highway speeds.