Speedo sender unit interchangability

alter the reading of the cars speed by replacing a sedans >Speedo module on the differential with one from a wagon .Or are they the same ?

225-60- 16 a more common size here and cheaper .My Wife has >195-60-15 on her 740 turbo could we go 205-60-15 a much cheaper tyre tire to buy , using the sender unit on the back axle .We love our >Volvos so we got our son a 1990 240 to learn on and boy its fun to drive ,with 195-70--14 tyres .

rear diff sender .Thanks from down under where the water >flows the other way or does it ?

All 700 series cars use an electronic speedo with a sensor in the rear axel unit. The sensor is the same, but the calibration of the speedometer varies with tire size. 240's used a mechanical cable speedo until '85, after that they got the same electronic setup as the 700's.

I wouldn't think so. Typically reluctor sensors are just a winding on a magnetized core, and they count the number of teeth that go by. A new sensor could change the output level but can't change the rate.

Mike

No, the calibration is in the speedo itself, I haven't looked into the details though, it might have a potentiometer you can adjust, or it might use soldered or plugged jumpers, you'd have to check.