The guibo's other purpose is to provide a "cusion" to the drive line to reduce short duration, high impact shock. It is very similar to a "cush drive" used on motorcycles.
If a solid metal guibo is used, something in the driveline might break, most likely in the transmission.

 

What’s a different material that would be more appropriate other than the rubber?

 

For the 5AT/7AT owners, I don't believe this is of concern. The MT guys definitely need to worry about this.

 

I don't think any other material would work for you manual owners. I suspect urethane would crumble in fairly short order.

 

I am not so sure about that... What about the jolt to the driveline every time the car is put into drive or reverse?

 

The torque converter is a fluid coupling. It cushions the blow. Granted, there may be enough driveline lash with an auto to make this a problem, but I doubt it.

 

Just a thought...
The Driveshaft Shop (https://www.driveshaftshop.com/impor...num-driveshaft) shows what looks like to be a replacement guibo in the bottom right: Maybe they will sell them seperately?

 

Bring back an old thread but was there any update to this other than buying a complete driveshaft replacement?