Guibos for V8 torque?, like the 917s Options

[DougC]

Hey guy I have an idea to handle torque to the 901s from a V8. It involves a rubber guibo or flex disc. My E30 M3 has one that fits between the drive shaft and transmission flange. Now, I was looking through a book I recently bought entitled "917 the winning formula" all about the great Porsche race car and others like the 907, etc. A great book with lots of pictures and the inside scoop on the early racing successes - I highly recommend. In one of the shots you can see very distinctly 2 rubber flex discs (guibos)between the half shafts and tranny on the 917. I swear from the picture they looked just like the one on my M3. Of course major mods to the shafts and tranny flanges would have to be developed for our application but do ya'll think this would help torque issues. Maybe the BMW parts could be incorporated with larger CV joints? What would be some of the most obvious hurdles? TIA.

Doug C

[lapuwali]

Most of the issues with guibos are durability and balance issues. Designing in the right amount of flex to allow the coupling to move as it should, yet still be strong enough not to be shredded quickly by torque, is not a task for amateurs. The only real place to use them on the 914 would be on the output flanges of the transaxle, replacing the inner CV joints. This would help with shock loads, but the relatively large angle they'd have to operate through to allow the suspension to move wouldn't suggest a long life for these parts.

Lotus and others used these in exactly this fashion on a number of race cars, but I don't know of any street cars using guibos in exactly this way. Street cars that have used them typically mount them between the gearbox and the driveshaft, where the angular changes are fairly small, so the rubber can be much stiffer and stronger. I wasn't aware BMW used them, but Alfa used them for decades as driveshaft couplings. Life in the Alfa application was typically 50-80K miles, and they're a serious pain in the ass to replace. Used as an inner CV replacement, I'd not be surprised to see a lifespan of no more than 10% of this, which I'd think would be unacceptable to most street car owners.