928 Driveshaft in the 944 Turbo GTR
01-06-2019, 11:11 PM
#1
Three Wheelin'
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928 Driveshaft in the 944 Turbo GTR
So I’m reading the new issue of 000, feature article on the 944 Turbo GTR.
My impression was that it was very little factory 944, a clean slate race build if you will. But it’s mentioned that it used the 928 driveshaft.
It is also mentioned that it broke those driveshafts, a feat I’ve not really heard of before.
Here’s where it gets good: the only unused 944 Turbo GTR, chasis 004, was restored and maintained by our own Greg Brown.
How cool is that?!!
So I gotta hear how and why it chewed through our driveshafts...
My impression was that it was very little factory 944, a clean slate race build if you will. But it’s mentioned that it used the 928 driveshaft.
It is also mentioned that it broke those driveshafts, a feat I’ve not really heard of before.
Here’s where it gets good: the only unused 944 Turbo GTR, chasis 004, was restored and maintained by our own Greg Brown.
How cool is that?!!
So I gotta hear how and why it chewed through our driveshafts...
01-07-2019, 03:11 PM
#2
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No doubt had something to do with the 650-750 horsepower........ and Yes Greg Brown has one !! I do not recall if it had the 928 torque tube it has been many, many years since I had the blue prints from Fabcar.......
01-08-2019, 01:34 AM
#4
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The torque tubes themselves broke. Keep in mind that Porsche spent almost 4 years perfecting the torque tube for the 928 application....changing and moving around the bearings, building frequency absorbers, changing the mass and moving that absorber around. The monster 944 GTR engines had completely different frequencies and harmonics than the 928 engine. Add in the solid engine mounts (which were rather "long and weak") and transmission mounts and the torque tubes had a tough life.
They eventually added some additional mounting support to the back of the engines to reduce the load on the torque tube. That seemed to cure the problem.
They eventually added some additional mounting support to the back of the engines to reduce the load on the torque tube. That seemed to cure the problem.
01-08-2019, 05:59 PM
#5
The 928 5-speed drive shafts are 25mm same as all the 944 drive shafts. The drive shafts survive surprisingly well in the many boosted applications that 928 and 944 owners have done over the years. The only larger one (in OD) Porsche made is the problem prone 928 automatic 28mm drive shaft which shears at the necked down point.
That the actual torque tube broke is not surprising since the 928 torque tube wall is actually pretty thin compared to a 944 torque tube which is longer but has a thicker wall. The torsional stresses acting on it when everything was solidly mounted and the torque that motor was generating must have been tremendous.
That the actual torque tube broke is not surprising since the 928 torque tube wall is actually pretty thin compared to a 944 torque tube which is longer but has a thicker wall. The torsional stresses acting on it when everything was solidly mounted and the torque that motor was generating must have been tremendous.