VTD SVX without rear wheel drive...

[jovaan]

Thought I'd share my experience from yesterday about how VTD spec transmission behaves without rear driveshaft. As we know US spec SVX's had different 4wd system, I think called AC-4 or something, that did not have center differential (clutch pack only) and was fwd biased. VTD is rwd biased and has center diff + clutch pack as locking mechanism.

So with driveshaft removed (for repair and balancing) I decided to try out latency parameters of that locking clutch pack. I plugged the driveshaft outlet from gearbox and took a short drive. I know this is very stressfull for gearbox, so we are speaking about less than a mile of testing and then back to garage. My findings:

- when you take off lightly, the clutch pack locks almost immediately and you can drive the car almost normally.
- when you do more aggressive take-off, things go wrong: the clutch pack does not lock (maybe transmission ECU senses something is wrong) and the rear drive just spins, speedo jumping to 60mph+ in fraction of a second. This is interesting find; relates to my finding earlier with very slippery surface driving. If front wheels are on asfalt and rear wheel on we ice, the car only moves with light throttle. If you floor it right away, the locking clutch pack does not engage. Same effect here without rear trans shaft.
- ABS naturally picks up speed difference between gearbox and wheel sensors and lights up the red warning light. No suprise there.
- Few take-offs later, you can clearly feel the clutch pack is not happy. Some vibration at take-off before it locks.

Interesting find for me was that with sudden radical difference in speed between front and rear wheels the diff lock does not engage.

Driveshaft is out for new joints, new rubber bush and bearing and balancing, hence the excercise...