Twisting Driveshafts...

[StretchASU]

So this isnt off road related but hopefully some gathering of the minds may help me pinpoint the issue...Mods feel free to move this if you don't think its in the right area. Just didnt want to throw it in general Chit Chat cuz of the tech.

A little background...

Roommate's dad runs a Datsun 510 Tube Chassis car in SCCA which I typically crew for and the car twisted a driveshaft in half at the Memorial Monster event at CMP a little while back. Its a former GTL car so no wild horsepower. Just the legal L series Datsun mill. Came home, tore the car down (dont know how extensively) for their typical post race inspection and put in the new driveshaft. Well they went out again today and the new driveshaft twisted in half again on the second warm up lap, less than 4 miles on it. Both times they twisted rolling into the throttle coming out of a corner. This car has been run/logbooked for 15+ years and this has NEVER been an issue.

Rear diff is a Detroit apparently. Anyone have any guesses as to why it is all of a sudden this car is killing driveshafts in the same scenario every time?

My first guess is that the Detroit is worn out and now when its grabbing coming out of that corner as the wheels sync up in speed, the shockload it creates goes down the line to the weakest link, the thin walled tubing driveshaft. No way the car has the power to break ring gears or axles on the little Hoosiers so that seems like it would logically be the weak link.

Just wanted to see what you guys think might be the culprit.

 

[RenegadeT]

any changes in the suspension, where the driveshaft length needs to change? Maybe somehow its too short, causing it to buckle/bend, then snap. my wild ass guess.

 

[92illpony]

i would open up the rear end and have a look.

 

[DAWGTOY]

any chance that the driveshaft is hitting the trailer when they load--unload the car?
it looks like it has rubbed on somthing.
all it takes is a small dent to start a big problem.


dawg

 

[GCncsuHD]

any changes in the suspension, where the driveshaft length needs to change? Maybe somehow its too short, causing it to buckle/bend, then snap. my wild ass guess.

any chance that the driveshaft is hitting the trailer when they load--unload the car?
it looks like it has rubbed on somthing.
all it takes is a small dent to start a big problem.


dawg

Both of these are possibilities. It's like a soda can, when it is in perfect shape it will support your body weight, but the slightest dent ding or bend and it collapses. All it takes is a small dent while loading on the trailer, hitting a driveshaft loop or body, rock, or the suspension movement allowing it to bind up, in turn bending the shaft a bit.

 

[GubNi]

Pretzel driveshafts are caused by small dents. Torque turns the small dent into a bigger dent and eventually you get a pretzel. Build the next one out of .120 wall tubing or schedule 40 pipe

 

[houdini]

As already mentioned... The driveshaft is either hitting something or rubbing on something.

 

[Reid]

any chance that the driveshaft is hitting the trailer when they load--unload the car?
it looks like it has rubbed on somthing.
all it takes is a small dent to start a big problem.


dawg

this is what i was gonna say.

any curbs, or pot holes, if you dont think its hitting the trailer, find what it is hitting. is there a new track he is practicing at? a new garage, maybe misplacement of the lift arms when the lift it up. a speed jack hitting it maybe?