I was thinking when you do a chassis dyno test you have it in 4th gear for a 1:1 ratio. I was wondering if they take the rear ends ratio to give the final #.

 

I don't think rear gears matter at all during dyno tests.

 

it shouldnt make any difference....its a 1:1 ratio, so you eliminate all gear advantage except at the rear end....but the variance isnt enough to make a significant difference in dyno numbers...cause all cars are pushing the same load on the dyno rollers

 

so the same car with 4:11s and 2:73s would put the same #s to the wheels?

It seems weird to want a direct drive through the tranny but not through the rear.

 

no, they won't put the same power to the wheels.

 

The same power will be measured (neglecting any trivial difference in losses between the two gear sets), but the 4.11's will have 1.5 times the rear wheel torque.

The pull can actually be made in any gear. The dyno corrects for gearing to give flywheel torque rather than rear wheel torque by inferring the ratio from the engine RPM and rear wheel speed of the car.

 

The dyno still gives rwhp and rwtq #'s.

 

4th gear is 1:1 in a manual tranny. 3rd is 1:1 in auto.

i've done a second gear run and a 3rd gear. gained 7 peak hp in 3rd (auto) and gained 71.1 peak tq