I have a 2008 H3 Lux with just under 50000 miles on the clock. I am looking to upgrade the 5cyl to the 5.3V8 that was released in the Alpha model. Is there any drivetrain issues that will be caused by the increased hp? The car is in Australia and I will be buying all the parts in the USA so would like to make sure I order everything in one shipment.

 

I might be wrong but I believe the Alpha models all had front and rear selectable lockers, and a 4:1 transfer case which is a big improvement over the under model H3's. Like I said I could be wrong but I think you are getting into more than you think.

 

I know how expensive it is to get US stuff down there and the exhange rate don't help, but I think I would be looking for a good deal on an Alpha instead of the path you are thinking. Of course that is just me. If I were thinking of an engine upgrade though, I would be trying to figure out what diesel engine I could stick in there.

 

Front and rear lockers and the 4:1 TC are purely an adventure package option. Many of the Alpha's I came across while shopping for my truck did not have this option.

 

The only "real" difference is that the 08 H3 Alpha has a cast iron front diff. and the I5 has a aluminum diff. If you are not going to take it OffRoad you shouldn't have any issues. There are several companies here in the states that precorm this swap but only 2 that I would ever let have my HUMMER.

08 H3/H3T: I5 Alum front Diff. 4:56 gears / V8 Cast iron front Diff. 4:10 gears
09-10 H3/H3T: I5 Alum front Diff. 4:56 gears / V8 Cast iron front Diff. 4:10 gears (Adventure/OffRoad I5 and V8 all had the cast iron front diff with Eton locker I5 4:56 / V8 4:10)

 

I am more concerned about the mech. requirements not the price or logistics of buying and shipping parts. Things such as if I put a V8 in my H3 will the rest of the car be able to handle it and not fall apart. The H3 and the Alpha have differing rear ratios, is this a problem?

Thanks for the replys keep them coming!

 

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I might be wrong but I think I remember that the frame was redesigned in the Alpha's to make room for the 5.3 along with the cast case up front. I still think your best bet is finding an Alpha rather than to try this conversion on the I5

 

I've read this same thing - that you can't just buy a 5.3 and bolt it in, need to modify the frame to make it fit.

 

I know the firewall was modified for clearance for the V8, but since you have a '08, I'm pretty sure the same firewall was used across the board. If you've got an '06 or '07 you'd be out of luck. I'd check into it to be sure.