Hello all,

Looking at the gearbox that I've taken out of my 1990 C4, it appears to have a speedo sender attached to it. My understanding is that from 1990 the ABS sensor is used for the speedo signal - if that is the case then why is the speedo sender still there ?

Is there a way to determine what is being used by the speedo ? The reason I ask is that I'm swapping in a later C2 gearbox which doesn't have this sender and would like to know if the speedo will actually work.

Cheers,

Talat

 

My 1990 C4 uses a transmission mounted speed sender too. If you want to try to determine if that sender is being used for your speedo, why not unplug it from the harness and take the car for a drive? The connector is on the side of the transmission.

 

Driving it might be hard to do.....

Marc

 

My mistake. I missed that "key" piece of info. Thanks for correcting me Marc.

 

Sounds like once it's all bolted together I'll have to cross my fingers and hope for the best

 

here's your solution if you have to: http://www.speedhut.com/ i got one on my 964 and it fits fine.

 

Many thanks. Will contact them if all else fails.

 

It depends on what model of PDAS/ABS controller you have fitted - early C4's had 964.618.126.00, this is for use with the gearbox that has the magnetic pick-up in the transaxle. Later cars (91ish) used a different gearbox and picked up the Speed signal from the front left ABS sensor, passed through the later version of the controller 964.618.126.01 and then through a frequency converter in the Central Electric box to the Speedo. More info at https://rennlist.com/forums/964-foru...hangeable.html

 

Would this explain why the speed read outs between my OBC and analogue speedo differ? When my speedo reads 50 mph the rear spoiler raises but the digital OBC reads 55/56mph...

 

Thanks for this, most useful. So it looks like Adrian's book is wrong then.