A crisp and sunny early Spring day here in northeastern Connecticut with that incredibly white sunlight only fleetingly on show at this time of year.
I wrapped the clutch-end of the TT so as not to tear up my (fragile) reskinning of the tunnel insulation. This being the later style design, you have to initially insert the TT into the tunnel rotated 180 degrees from its normal position, to clear the severe-looking barbs on the TT itself and the matching pair on the rear suspension torsion bar tube. To do this I needed more clearance between the body and the already-dropped rear suspension - you may recall I couldn't lower the rear suspension much because the scissor lift was in the way - so I momentarily jacked the body up by the rear cross-member (usually obscured by the gas tank), and Bob's-Your-Uncle, was able to twist the TT to its correct orientation.
I have not enjoyed seeing the rear suspension out; it made the car look discombobulated and the project somewhat out of control. That said, today I saw it with new appreciation having read an article by Karl Ludvigsen in the new/June issue of
Excellence, about the development of of the 964 C4. We likely all know that the 964 was the first production version of the 911 to use coil springs on all four corners, as opposed to torsion bars, but as to why Porsche clung to this design for so long was interesting.
While the front suspensions of Porsche designed production vehicles had moved on from the front trailing arm/torsion bar set-up of the 356 and Volkswagen's (Beetles, Buses, Karmann Ghia's, etc) to a McPherson strut design (albeit still sprung via torsion bars, but longitudinally oriented), the rear suspension design, with it's torsion bars mounted in a lateral tube, stayed right through to final 1989 Carrera.
The 964 needed to get rid of that tube because it was in the way of the driveshaft required to transmit power to the front end. What Ludvigsen reveals is that the old, lateral torsion tube design had been something of a Sacred Cow within the Design Office because it was still an active Porsche patent, and was therefore still earning income for the Porsche family. Accepting that the design had reached the end of its life, at least in the 911, was apparently a bitter pill to swallow.
[img]http://forums.pelicanparts.com/uploads26/964C4_cutaway1584310510.png[/img
I'll admit that I'd never realized the 924/44/68 family had also been designed around this same rear suspension layout until I got this car and saw the same hardware which had become familiar from the SC.
With this round of work, which started with me needing to get the fuel tank out for cleaning, I'd taken the car further apart than initially planned, and today was pleased to see it going back together. The fact that the rear suspension is a removable unit in this family of Porsche's, as opposed the 64-89 911, where the torsion tube is laid down as the car's first element, like the keel of a ship, is far more sensible and the way it is bolted to the unibody is rather elegant. Finessing it into place, both floor jacks offered service, a bit like tug boats nudging a barge into the port.
I still need to install two more brackets locating the TT within the tunnel...not easy to get at on this lift. But as I was sweeping-up, one thought came to me: I'd be a
complete and utter nitwit to try using a pre-owned clutch assembly in this car (to save money). No way I want to repeat all of this work.
Best wishes and good health to all of you and your families in these odd days.
John]