A friend of mine has an 04 colorado with the 3.5. He wants to do a v8 swap eventually and when I mentioned the gen VII 8.1/allison trans he got all wide eyed lol so I was just wondering if it would be possible to do this swap? what all will I need? Can the stock rear axle handle it?

 

That engine and tranny is way to heavy to be practial in that truck. Just do a 5.3 and 4l60 swap. Its much easier and would be a hoot to drive. Thats just my 2 cents

 

Skinny, what do you mean by practical? thanks for your opinion =)

 

Custom headers for the 8.1 would be high dollar. That allison trans would drag the ground without doing major tunnel work. You can make alot of power with a 6.0 or 5.3 for reasonable cost. The 8.1 doesn't have a big aftermarket following. Heads cams intakes ect

 

ok, Thank you for explaining that. The trans dragging is definitely a huge issue. would a 4l80e be a better option? I think they used that trans in the avalanche 2500s

 

cost wise a 5.3 or 6.0 swap would be alot better, and 285-325hp in a colorado is more than plenty.

 

Just what he said^^^^

The 4l80 is a beast to, Its alot bigger than the 4l60. Go with a built 4l60 with a 400hp motor and it will be nasty.(auto colorados come with 4l60)
Im building a colorado with a 5.3, 4l60, and a big nos bottle lol
I will be starting mine in a few months so ive done a ton of reaserch. Mine will be used as my DD so im going to stupid so I can keep reliabilty.

 

The i5 performs well with boost if he just wants a nice jump in power

 

Big block sounds cool,but not to practical when you can do a LS1 or any of the truck V8's and weigh a whole lot less and get just as much power.

 

He may have to do an axle swap. I am not sure what rear end the colorado uses but If it's smaller then the one in the 1500 silverado's which is refered to as the 8.5/8.6.

I dont know for sure but some of the info I found says it may have an 8.0 ring gear.