Just curious,

How much HP is lost when it finally gets to the wheels?

EDIT: On a 4t65e-hd tranny.

20% is standard practice I think...

Ive heard 30-35 loss. percent

20% for automatics and about 15% for manuals.

Depends alot on drivetrain layout too. FWD vs RWD vs AWD. Generally the more complicated the more power loss.

I have heard 4T60 series including the 65 and the E loses 26% power and the 4T80E loses 24%.

Sorry I cannot remember the source, but thats the 2 numbers I recall.

According to Scott Cook, IIRC, depending on torque convertors and if the tranny has built up internals, the 4T65E-HD has 18-22% power loss. So, generally I just use 20% for my calculations as it is a nice round number, and its right in the middle. And, as a general rule, the loss is 20% for auto'* and 15% for manuals anyways, so that makes it seem like that much better of a number to use. You can't be sure what the loss is, so you pretty much have to approximate. The stupid Chrysler trannys (the ones that they use with the FWD 3.5L engine) have like 32% power loss or something like that because of how they are setup.

Shawn

The Automakers should rate their vehicles by Wheel horsepower instead of Brake horsepower.
The differences in efficiency accounts for why some cars with less hp and weigh the same as another, can accelerate quicker. That Chrysler 300 M being a good example.

ryan-nomics uses about 15-20% crank loss... i usually get a nice medium

I use 20 percent (as pretty much stated above).

whp / .8 = crank hp

Looks like 20% seems to be the general consensus.