Here, the dyno shows a 1.1 horsepower and 5.0 ft/lbs torque difference between the stock steel driveshaft and the 1LE aluminum driveshaft. This might not sound like that much, but it also produced an AVERAGE gain of 1.8 horsepower and 5.5 ft/lbs torque. This mod is free (if you have an unbalanced stock driveshaft there is a TSB about the problem) and is definitely worth the 4 hours the dealer needs your car. Check out the Dynojet Race Routine between the stock and 1LE shaft.

Note: All runs were performed with the car at approximately 180 degrees at the start of the run.

While I could not feel the gains in power from the driveshaft, I did notice that 90% of the vibration caused by the inbalance of the stock shaft has disappeared. In the future, I would like to go to a larger diameter aluminum shaft, like the Lingenfelter 3.5" or maybe a carbon fibre shaft. A larger diameter shaft would be smoother and have a higher critical speed. The stock shaft has a critical speed with stock 3.42 gearing of 153 MPH. Given that the cars will do that stock, I do not feel that they are safe. I'm sure that was one reason GM is going to a 3" aluminum shaft for the 1998 F-body.