What is the axle ratio for an '03 auto versus an '03 6 spd? I'm thinking this may be the reason the percentage differences are so close on the dyno. For an '05 auto it is 2.44:1, for an '05 6 spd, it is 4.13:1. Are these numbers similar for an '03?

 

Gear Ratios 4sp A/T
--------------------
1st 2.785
2nd 1.545
3rd 1.000
4th 0.694
Reverse 2.272
Final Drive 3.789

 

Thanks! I guess because of the extra gear in the 6th gen, the gearing is a lot different. Do you know the numbers for the 6 speed?

 

2002 6-speed ratios:

1st 3.153
2nd 1.944
3rd 1.392
4th 1.055
5th .809
6th .630
Rev. 3.002

F/D: 3.81

 

Thanks. That blows my dyno theory, then. Gear ratios effect your dyno numbers and I thought this might be why the percentage difference between autos and manuals were closer than in other cars I've seen.

When dynoing, the transmission is in the 1:1 gear ratio (3rd in the auto and 4th in the 6spd). The axle ratio can then skew the dyno numbers. The closer to 3.5:1, the better. If it numerically higher, it skews the dyno reading down and vice versa. For example, changing from a 3.42 gear ratio to a 4.10 gear ratio in a Corvette or Camaro, lowers your dyno reading by approximately 10 whp and 10 ft-lb.

Seeing that the axle ratio is so close on the A4 and M6, it must be the tranny losses are just closer than I'm used to.