It would make more sense to have one in the transmission so the computer would know the base speed the wheels should be turning. They could more quickly determine if one or two wheels where spinning to fast of slow. They could compare each wheel to the transmission sensor instead of comparing each wheel to the other three. a lot less math in the computer.

 

CRAP! Now I have conflicting information from this site. In this thread and in another that I can' seem to find right now, it is explained that the Speedo uses the ABS to measure tire revolutions to calculate speed.

Now I'm gonna have to crawl under the Jeep and take a look.

 

If Jeep uses a similar algorythm as Bosche Motronic used in the VW, Audi, Porsche the wheel speed sensors are used simply to check for wheel spin by comparing the values. there is an allowable threshold due to wear, inflation.

 

THe assumption that the wheel speed sensors has any affect on speedometer reading is incorrect. The wheel sensors are only used for the ABS programming......and all those other electronic thingies the Jeep has....ESP, BAS.....traction control....lord, don't let me leave somethin out. The speedometer gets it's input from the trans sensor ONLY. This is why the speedometer WILL STILL OPERATE with the driveshaft REMOVED. Were the wheel sensors involved with speedometer input, this would not be the case.

 

You mean the speedometer will show you are moving if you try to drive away with the driveshafts removed? but if you are towing the Jeep with the driveshafts removed the speeometer will not work?

 

I mean while in the air, on a lift, with the rear driveshaft removed, yes the speedometer will still work when the Jeep is put in gear. No, if the Jeep is being towed with the rear driveshaft removed, the speedometer will not work. The transmission output shaft must be turning.