I got a 2001 Suburban with a 8.1 Vortec and a 4L80E Trans. A freind has a Allison trans out of a 04 Silverado with the 8.1 engine.My question is. Is it possable to change out the 4L80E with the allison?
Thanks in advance;)

you'll need to do a body lift, among other things, to make the Ally even fit.

Then theres the wiring/computers you'll have to deal with....

definetly not impossible, but be prepared to deal with some big issues requiring "custom" work. ;)

ben

you could sell a working allison for more money than you need to build or have built a MONSTER 4L80E with all the heavy duty goodies
just a core allison goes for close to $1500