God was watching me when I bought the 4T80E... I bought it as a high-mileage core for 150 bucks. Well, it'* just been rebuilt! I bet it doesn;t have 5K miles on it.
I went thru and did a couple shift mods. I firmed-up the accumulators, removed the cushion spring on the 4th band apply servo (shimmed it solid). I was going to add clutches to 2nd and 3rd clutch packs, but when you see the pics, you'll know why I didn't. All I did was remove the 2nd wave plate to give the pack real clearance (and a hard hit 1-2 shift). I also removed 4-of-12 3rd piston return springs and a few 2nd piston return springs, too.
So, I guess I'm going thru with the swap... now it'* fabrication time!
chain drive gear
2nd clutch, about 8" diameter x 5 frictions
3rd clutch drum, 6" diameter x 4 frictions, front planetary, 2nd clutches
rear planetary, forward clutches behind (didn't change anything past this point)
1" drive chain and driven gear
huge roller bearing supports each chain gear (4T65E uses a needle bearing cage about 1/2 the diameter)