Porsche 917 question
 

What are the circled parts which appear to be attached to the driveshafts?

Counterweights? Vibration dampeners?

http://forums.pelicanparts.com/uploa...1258510333.jpg

917-style CV joints?

Also used on 935, GT40, some formula cars (Formula Ford for instance) and of course...the Hillman Imp.

In different sizes.

Look like giant flex discs to me.

Yes! the Mighty Imp!

I can't recall the name but I think they were used in conjunction with the universal joints to dampen the shaft speed variation that is inherent to the u-joints. Also guessing constant velocity joints with "constant" shaft speed were not strong enough for such applications?

PS Ok I remembered "guibo" but I think that just means a flex disc.

Just stole this definition :), sums it up nicely
"The guibo serves as an interface between the transmission and the driveshaft. Since the guibo is primarily made from rubber, it acts as a damper when shifting and engaging into gears, so that the transfer of power to the driveshaft is smooth and dampened, instead of abrupt and harsh."

917, abrupt and harsh, never!

A couple of years ago, I sold a NOS Hillman Imp transaxle to a guy for use behind his Coventry Climax engine. Still had some cosmoline protectant on it after sitting around for almost 40 years. Don't remember the guibos though. Some Alfas used guibos to connect the trans output shaft to the driveshaft as well...

http://forums.pelicanparts.com/uploa...1258518033.jpg

Guibo is the word. We used to call them rubber doughnuts.