Broken JCI driveshaft?

[boyracer]

Thanks for the pics. I haven't run the new fuel lines yet and I may add a DS loop sometime in the future so I don't want to go too big.  

[RebekahsZ]

For the driveshaft loop, consider one that bolts to the two bosses on the transmission tail housing. I considered it but didn't do it for fear of insufficient strength. I've since seen some torque arms mounted to those bosses, so I'm now sure it would have been ok.

[Tony D]

I run a 3" Aluminum.

 

The Boyracer driveshaft looks like a polymer-bonded unit. The two tubes are bonded by vulcanised rubber of various durometers depending on how much torque you want to absorb to save components downstream in the drivetrain.

 

This was the ONLY way Porsche kept the 917's on the road. The axles were constructed like this, and the telescoping and torsional absorption provided by the elastomeric insert was the only thing that could transmit the torque without shattering.

 

Curiously, if that shaft is constructed properly, with enough overlap inside the tubes, should the elastomer fail, the driveshaft just "sags" it can't come out and vault you. Some guys I know drilled holes to allow putting a screw in should it ever delaminates so they can wedge the pieces together and at least limp home from the track, or drive back onto the trailer.

 

Carbon Fiber does not require a driveshaft loop due to its construction.

 

Our times showed improvement going from 2.5" steel to 3" Aluminum. I forget how much, but you could feel the weight difference. We isn't think it would make that much of a difference, but it did!

Edited February 18, 2013 by Tony D

[boyracer]

For the driveshaft loop, consider one that bolts to the two bosses on the transmission tail housing. I considered it but didn't do it for fear of insufficient strength. I've since seen some torque arms mounted to those bosses, so I'm now sure it would have been ok.

 

Good idea, I was just going to remove that piece!

 

I run a 3" Aluminum.

 

The Boyracer driveshaft looks like a polymer-bonded unit. The two tubes are bonded by vulcanised rubber of various durometers depending on how much torque you want to absorb to save components downstream in the drivetrain.

 

This was the ONLY way Porsche kept the 917's on the road. The axles were constructed like this, and the telescoping and torsional absorption provided by the elastomeric insert was the only thing that could transmit the torque without shattering.

 

Curiously, if that shaft is constructed properly, with enough overlap inside the tubes, should the elastomer fail, the driveshaft just "sags" it can't come out and vault you. Some guys I know drilled holes to allow putting a screw in should it ever delaminates so they can wedge the pieces together and at least limp home from the track, or drive back onto the trailer.

 

Carbon Fiber does not require a driveshaft loop due to its construction.

 

Our times showed improvement going from 2.5" steel to 3" Aluminum. I forget how much, but you could feel the weight difference. We isn't think it would make that much of a difference, but it did!

 

That sounds like what mine looks like. There is some kind of rubber-like material sandwiched between the two tubes, may be able to see in this pic.