Driveshaft discussion.
A semi-common problem is worn u-joints/carrier bearings.
A lot of times carrier bearings and u-joints can be mistaken for one another.
Worn carrier bearings cause a loud/violent thump when shifting or under hard acceleration, and can lead to bad u-joints.
Bad u-joints tend to shake when shifting and a bit under light acceleration, but at higher speeds there may not be any vibration.
Want to make sure? Jack it up and get under the car, grab the driveshaft and try to move it, it shouldn't move. If you are getting obvious movement, you need to replace hte carrier bearings. Check out these links:
http://www.penguinhosting.net/~bigma...riveshaft.html
The carrier bearings are $60-65 each at Norco
951-735-7100 (That maybe with the 3si discount, I'm not sure, but if they quote you higher and you are a 3si member, I'd mention it)
Bad U-joints however aren't really serviceable, and therefore not as cheap to replace. At this point, you typically have to replace the entire driveshaft so many go with a lightweight one. The lighter the driveshaft, the less rotational mass, and therefore the less hp is wasted trying to spin it, this basically means less parasitic drivetrain loss and therefore more of hte hp your engine is making makes it to the wheels/ground.
Currently there are a few carbon fiber options, and I believe possibly an aluminum driveshaft or 2 available as well (but I'm not positive). You can get 1 or 2 piece driveshafts. The 1 piece are lighter, but some complain of vibration issues, and opt for the 2 piece. I have heard PST will assist you if you order hte 1 piece and later decide to switch to the 2 piece...they also offer a $100 3si discount.
http://www.pstds.com/carbonfiber.htm
Dynamic Racing also sells ACPT CF driveshafts at:
http://www.dynamicracing.com/customer/home.php?cat=117