2 bent dirve shafts???

i got a guy whos bent 2 drive shafts.

the car is a ls1 f body. he is the original owner, road races but doesnt drag race. the car is pretty much stock.

the first drive shaft bent with original suspension. at speeds of about 220-230 km/h. well some serious vibrations were met.

then it was replaced by a shop with a steel drive shaft for temporary use. tested it, ran fine for a bit at speeds of 220 km/h. then a short while later the vibrations came back.

went to the shop again, it was bent.

the only differenced between the two times was the second time he had some suspension mods done like new konis, relocation brackets, eibach pro kit, aluminum lcas.

now what the hell would cause two drive shafts to bend at speeds of over 220km/h???

never heard of a driveshaft bending .. they break . not bend .. weird..

Actually bending and not just unbalanced? It would sound more reasonable that both d/s were faulty to start with. But who knows. ?

well the shop he took it too said it was bent. so they built him a steel 3 inch one. then that bent, so they said he over spun it.

hes going to take both drive shafts to another shop for confirmation.

Im with ChriSS on this one . . . what rear gears does he have ?? I highly doubt he over spun it but maybe with 4:10 and 270 - 280 kph ?? We topped out the TA a few times and everything was fine.

Maybe he should concider a carbon shaft :eek:

If you use U-joints that are not rated for constant use at high speed(like a road race) and pinion angle isn't perfect it can cause that drive shaft to bend. I can get more into the explanation if you want

I'm thinking that bending a "weak" drive shaft would be pretty easy. This is a wierd example but think of when you used to make snakes out of playdo. When they were first rolled into a "tube" they started out thick and you thinned it out by rolling it, etc. Well another way to make it thinner was to grab both ends and spin it like a jump rope. At first it wouldn't bend but the faster you went the more mallaeable/flimsy it would get. The ones that break probably have a greater resistance to being flexible and instead just break in half. I'm just guessing, and I know nothing about driveshafts, but it seems to make sense. Just my 2cents. ;)

I see having children has already tainted Mr Bains :irk:

If you use U-joints that are not rated for constant use at high speed(like a road race) and pinion angle isn't perfect it can cause that drive shaft to bend. I can get more into the explanation if you want


please do so i can forward all the info to him.

as far as i know the u joints were stock. the pinion angle did change after he lowered it using relocation brackets but we dont knwo why it bent in stock suspension mode.

rear end is stock

He is running the driveshafts above their critical speed. The factory driveshafts critical speed is probably 6000-6500rpm. At that point the driveshaft begins to bow in the middle because of the slight unbalance. Ways to correct this are: shorter shaft, thicker tube, larger tube, better balance. Carbon fibre increases the rpm because it doesnt flex as much but it will shatter instead when it gets to its critical point. To find out the RPM the driveshaft is spinning just go to an engine rpm calculator and enter the tire size, gear ratio, and speed but leave the tranny ratio at 1:1. Thats how fast your poor little DS is spinning.
Cheers.