The 996.1 gearbox does not have a speedometer cable, so how does the car know how fast it
is going? It has to know what gear you're using in addition to the engine rpm. How does it work?
Same question for the odometer.

 

dont quote me on this, but I thought I recall it used the speed sensors in the rear wheels. Not sure though :/ Im curious now as well.

 

My understanding is that manual 996's use one of the ABS encoders (sensors) to calculate vehicle speed. Front left, I read somewhere - but I won't swear to it.

 

This may enplane why my speed did not change (based on the roadside speed signal's) after putting on my new 19" wheels. The rear tires are approx 1" larger than OEM so figured my actual speed would now be same as speedometer speed but my front tires are approx same dia as OEM. C2 Coupe not a C4

 

 

Great, now can you explain in lamens term what term. 15, term.58 or term.86 S means? I know there has been other threads covering that the Porsche speedometer seems to read lower than actual speed and again when I installed larger diameter tires (rear only) I was expecting for my actual speed to be more consistent to the speedometer speed.

 

Tested mine the other day and it was 4kms under

04' C2 manual with standard size wheels and tyres

 

 

For my 98 C2, the speedo sensor was in the rear (can't remember if it was left or right). The sensor block (that holds speed sensor and brake sensor) crumbled and I lost my speedo so I had to replace the wiring harness that runs from the wheel to the rear circuit panel. Ended up doing all four corner within a month.

 

For what it's worth, it isn't entirely accurate, either.

When mine says 70mph, I'm really going 65 - 66.

When it says I am going 30, really about 27.