that zf shifted like butter. That was my first introduction to quality transmissions. I’m either gonna go with this 80 conversion swap kit or a built 65e from an online source

 

Its going to be a few months before ill be able to tackle the swap. Got too many customers vehicles in the way. I've got a buddy with a LT4 vette with all the bolt ons and cam with nitrous on C85. It goes 5.5s in thr 1/8 pretty consistently but he is on his 7th 8 speed and 4th diff.
for reliability sake id go 4l80 and not look back.

 

I soooooo wanted a 6l80e or 6l90e in my tahoe, but the 4l80e swap is tried and true, simple enough, cheap enough, and the 4l80e is beyond proven.

I local guy did a lsa/6l90e swap from a zl1 in love a tahoe. It is amazing, sweet truck; but he had a fit getting it all settled and correct. He told me he spent around $6k on it after it was "finished" trying to get it right.

Simplicity is where the 4l80e shines in a gmt800 chassis. Almost all oem parts can be used. Even for your 2005 denali bw 4481 transfercase; someone on here used parts from a gmt900 bw4485 to make the 4481 32-splines for the 4l80e and it ran like factory. For my tahoe, I got an autotrac case from a suburban 2500, no computer changes.

Thst said, I would LOVE a 6 speed, or even a newer 10 speed

 

Had mine built in the valley going on 5 years ago pretty much every upgrade you could get at the time plus billet input and output shafts. Total cost was around 4k with them pulling and installing it most of that cost was the shafts. 50k hard miles and it doesn't miss a beat just a bolt on 6.0. But the builder told me make sure your tuner is good because they can kill your transmission very easily too and a big tranny cooler helps.