Speedometer problem

[BSchweers]

I know this has been discussed before and I have read several posts on this but still have not figured why the speedometer reads 50 Mph when you are doing 70 mph and it does fluctuate a little.



I have replaced the sensor on the differential with no change in the situation. I also checked the new sensor for any metal filings after I had installed it.

Funny thing is if I disconnect the sensor on the rear differential the speedo is smooth as silk and the cruise will work. Of course the ABS and Brake light are on. Plug it back in and speedo starts acting up. At one point I disconnected rear sensor on diff and two plugs on the transmission and speedometer was still working smoothly.

Does anyone know where the second sensor is located for the speedometer?

Any help would be Greatly appreciated.

 

[BSchweers]

I also put dielectric grease on the diff sensor and the two connectors to the abs controller. Also checked for a short or barewire.

Anybody with some ideas????

 

[rbattelle]

I think the ABS tone rings at the front wheels are also used to sense vehicle speed.

Ryan

 

[BSchweers]

Well I figured out what was wrong!
I had the pinion seal replaced about 6-8 months ago. I pulled the differential cover off and found the small set teeth that the sensor picks up on for the speedometer were ground away. A bolt that holds the spider gears(I think) came loose and wedged it self under the ring gear. It actually pushed against the diff cover and almost punched a hole.

Well I called the shop and they are going to fix it with no cost on my end.