Mark42
Fleet Admiral
- Joined
- Oct 8, 2003
- Messages
- 9,334
My 98 Pontiac Firebird came with 3.08 rear gears, but I "upgraded" to a 3.73 set of gears.
I noticed with the 3.08 that around 80 mph there was a distinct vibration in the car. Not driving that fast often, and assuming it was due to tire balance I didn't think much of it. But, after the 3.73's were installed, the drive shaft is turning faster for the same vehicle speed as with the 3.08. Now I have that same vibration at about 68-72 mph, where I drive often. Because the vibration dropped with the change of the rear gears, and nothing was done to the wheels/tires, I am assuming the vibration has to do with the steel drive shaft.
I have read much about aluminum drive shafts, and GM puts them in their performance cars that have high speed tires and high speed capability (like Pontiac Trans Am and Corvette where speeds up to 130+ mph are attainable). The shafts are about 16 lbs lighter than the steel counter part, and are better balanced.
So rather than mess around with trying to balance my steel shaft, I found a low mileage aluminum shaft from a Trans AM (same length as is used in my Firebird) cheap. Going to pick it up this weekend.
So now the point of my post: What other benefits are there to aluminum drive shafts besides a weight savings and better balance? I have read where there are HP gains in the range of 2-5 hp are to be had, and others say no. Some say the car will accelerate quicker due to reduced rotating mass weight, others say no. Some say 2 hp savings due to parasitic cost of spinning a higher weight shaft, others....
Just wondering what members here can toss in.
Thanks,
Mark.
I noticed with the 3.08 that around 80 mph there was a distinct vibration in the car. Not driving that fast often, and assuming it was due to tire balance I didn't think much of it. But, after the 3.73's were installed, the drive shaft is turning faster for the same vehicle speed as with the 3.08. Now I have that same vibration at about 68-72 mph, where I drive often. Because the vibration dropped with the change of the rear gears, and nothing was done to the wheels/tires, I am assuming the vibration has to do with the steel drive shaft.
I have read much about aluminum drive shafts, and GM puts them in their performance cars that have high speed tires and high speed capability (like Pontiac Trans Am and Corvette where speeds up to 130+ mph are attainable). The shafts are about 16 lbs lighter than the steel counter part, and are better balanced.
So rather than mess around with trying to balance my steel shaft, I found a low mileage aluminum shaft from a Trans AM (same length as is used in my Firebird) cheap. Going to pick it up this weekend.
So now the point of my post: What other benefits are there to aluminum drive shafts besides a weight savings and better balance? I have read where there are HP gains in the range of 2-5 hp are to be had, and others say no. Some say the car will accelerate quicker due to reduced rotating mass weight, others say no. Some say 2 hp savings due to parasitic cost of spinning a higher weight shaft, others....
Just wondering what members here can toss in.
Thanks,
Mark.
