What percent of hp is lost through the tranny,drive shaft,and rear end?

I just went through this and my #`s don`t jive w/me et. I have a loose 8" vert which may have something to do w/it but, I`ve seen guys going MUCH slower than me puttin down some big #`s so,

Some will say from 15%-20%, it will vary on the
build of the driveline with the trans and diff used

I was told I was when I said 15%

For me, it has been a range of 17-19 percent comparing engine dyno numbers to chassis dyno numbers. I'm using a 9.5 inch race converter that kills wheel power, but obviously you need it to get down the track. A lock up converter, or a manual is more like 12-15 from what I've seen with others. My engine dyno numbers come from a dyno that uses Depac sampling, so I trust the engine dyno more than the chassis dyno. When you think of everything going on in the car I'm surprised it isn't more of a loss. I know when people do the loss converted to heat calculations it should melt the polar ice caps, but it is what it is.

I have not done the engine dyno for a comparison, but I have been told the transmission takes quite a bit of the power. Also, some power will be lost to accessories (radiator fan, alternator, power steering, etc), and having a full exhaust system (in a street car.)

100-110hp I have seen lost on a BB mopar 727 trans at the +600hp level...

Yup - and include the tire pressure, tire carcass type (radial vs. bias), tread width, weight of the axle lube, driveshaft angle under load, ATF temperature, Converter efficiency, line pressure, blah.

For automatic cars without a lockup converter we have consistently seen 18-19% loss at the wheels. This is on cars making between 700-1500 hp on an engine dyno.
Not sure on the brands of engine dynos but our chassis dyno is a Mustang IMP-SE with a 600hp eddy current brake and is very accurate/repeatable.

My low deck made 830 on the pump and with a full ex with tail pipes made 700 at the wheels...(std trans)

21% on mine, FWIW.