I have a bowtie overdrives TV cable kit on my hudson. It works exactly as advertised. Good quality stuff, if you are looking to go that route.

 

ok, so what about this. i hear everyone talking about how much parasitic loss the "80" has, yet it is supposedly a "400" with overdrive. what gives? is there really that much loss with the "80"? who can explain this? i talked to Carl Rossler at his shop over xmas and he said the same thing, but we didn't get into discussing why the "80" is such a power hog. he also recomended a "400". i just don't want to loose OD or pay big bucks for a GV OD unit.

 

the 400 kills power also, but it allows for different ratios, t brakes and all that stuff to get more out of the tranny than the 60 allows. the 80 and 400 only differ in the OD from things i've been told.

 

The low gear planetary from the TH400 will fit a 4L80E,but you don't need it.My 4L80E with a 3500 stall launches as hard as the 4L60E with a Yank 3000 despite the taller first gear,the Tahoe wants to jump sideways when it hits second and barks third gear hard,that's with 3.73 gears.I sure don't know where the power loss is.The transmission is nearly stock with the red high performance clutches and a TCI shift kit.

 

It's not just an OD tossed in it, it's more internals for it too. There are more clutch packs to go through (the 4L80E uses clutch packs for the forward gears in normal driving). Same as the Ford AOD (until 4th gear) and the Allison 5 speed... there are no bands for gears, only clutches and they sap power.

But we are talking what maybe 5-8% more over a built auto that saps usually 20-25% anyway, but with the extra holding capacity I would not be concerned with it.