Well the 4l80e is basicly a th400 with overdrive so I'd say you could'nt go wrong there. As a tech member for LS1.com I understand some of what you're talking about.. However Hummer is new to me and I'm still feeling my way through things. I too have a few builds under my belt, including an all one off twin turbo LQ1, and a few N/A motors.. My appologies if I wasted your time..

 

lol, you didnt waste any time. Besides it appears you have the correct color H3. I have to respect that.

Since you have LS experience you may like what I'm going to do. Its just for fun but I dont want reliability affected.

The issues with the 4L80 are fitment. The 4L80E is longer and has issue with the frame.

I'm told by RMCR in Colorado Springs that the stock trans does a lot better with a better converter and valve body. What seems to fail first in the 4L60? Clutch packs? Why would a valve body help strength?

Mine is fine but I want it upgraded forst before I waste money on more power. Im not looking to make 0-60 unreal. Im more interested in 10-60....not the dig. Is that a game changer?

 

Yeah there are clearance issues with the bell housing in the ls1 f-body and the 4l80e.. Have to mod the tunel a bit to make them fit..
One of the main issues I see and hear about with the 4l60e is the sun shell cracking. The papers in the packs are sometimes noted for failure aswell.
Many like to use performabuilt trany's for their high powered ls cars. May give them a call and see what they can tell you about your plan. Good folks there. The 4l60 is and old design and is derived from the even older 700r4 so there's all kinds of dirrections you can take it. As I'm sure you already know, performance and cheapness rarely go hand in hand. I would also upgrade to iron front diff housing, and an iron 4:1 t-case. Toss in a front locker if you plan on getting into the woods/mud/climbing.. I can't answer anything as of yet on the valve body because I have'nt heard or seen any proof of failures other poorly installed shift kits. You need an expert for that one.

 

Here's a link to a step by step performa built stage-2 4l60e.
Be warned though if you join there won't be much love for hummers..lol
I posted in the truck section and you'd would have thought I curb stomped a baby..
LMAO!
Performabuilt or finish line transmissions?

 

Here,, this will get your there faster if you are interested.

PerformaBuilt Level II - Pro Race (Build Pics)

 

Wow, the hate in the truck world vs cars is pretty bad I guess.

Anyway, your link to the Pbuilt trans is impressive. I will call them early next week. The kink is they need our core to build unlike the older 4L60's where they source a core. The issue here is that its not a single day swap and requires the truck to be laid up for 2 weeks between shipping 2 ways Colorado to Pa and back with a 2-3 day lead time.

Its 2k plus a converter at around 900 more. At least there is a performance increase with the trans swap.

 

I put a raptor jr trans with a monster sunshell in my h3t. I believe it is a beefed up 4l60 . I also added a Thor parts front drive shaft. The front diff ring and pinion is not super strong.