My speedometer is again acting intermittent. It goes for months without a hitch then it quits for anywhere from a few miles to many miles. Not every day. It’s more likely to happen with severe weather change. Hot to cold, dry to wet, thawing to extremely cold.

I’ve looked for the sensor on the rear end and haven’t found it. I don’t even see any wires around the rear end.

So where do I look?

Has anyone got a picture of the sensor location?

Are there wires I might look for....under the hood....visible under the dash?

I’d hate to have to pull the instrument cluster but I could if necessary.

Keep in mind this is a ‘99 3500 dually, 5 Speed no mods except Smarty on #1

I forgot to read codes, I’ll do that tomorrow.

Thanks

Byron

 

An easy check - when the speedometer acts up, does the odometer act up too?

If speedo weird and odo OK you have an internal problem with the speedo, since the odometer uses the same pulses to rack up the mileage.
Odo sticking while speedo showing zero looks like no signal to the instrument.

The sensor should be on the center of the axle, and have a twisted pair of wires in a sheet go to the drivers side of the frame.

 

Ok thanks,
Yeah, the OD doesn’t work when the speedometer doesn’t work. So no signal.
There should be room in the shop this week end so I’ll go and take another look.

 

On mine It's a small unit on the top of the pumpkin. One small pair of wires going to it from above too. Pretty easy to miss.

 

Well I found the thing. It’s on the left top just forward of the rear cover mounting boss. It’s easy to miss. Mine is covered in fresh salt corrosion, looks like something from the salt flats. Yuk. It looks very much like the crank position sensor. Also looks like it could be broken off easily. Since I don’t have a hoist avaiable any more I think it will be best if a shop breaks it off rather than me.

I also discovered my right rear shackle is broken and the left one is soon to follow. I’m going to order new ones tonight.

 

Get new bushings for the springs too, and check the leaf springs for cracks.

If the bushings get stuck stuff tends to break, and you will not want your axle to become independent from your truck

 

I got new spring bushings ordered too.

I was surprised the shackles rusted out when there is not much rust elsewhere. The brackets looked good but they are coated with something smooth.