my 1993 F-350 is going to be used for hauling firewood from the mountains so i needed a truck for daily use . i found a 1995 F-250 4x4 with 88,xxx miles on it for $1400 . it has a 460 with a 5 speed and is in great shape . it sat for awhile because of gas prices (9 months) i had to put in a new battery, a right side front brake caliper as it was seized up and a turn signal switch . so i take it for a test drive and everything works as it should except that the speedo is bouncing from 40 to 80 mph going down the road .......so i replaced the speed sensor on the rear diff and it made no difference

any ideas guys ....(i hope the speedo gauge in the dash isn't shot ) thanks and merry x-mass .....rich

 

Sounds like speedo gauge, check your wires for damage.

 

thanks for the reply rugermack ....
i dont want to just throw a new speedo in and hope for the best ....has anyone ever had this happen to them in the past and figured it out ?

 

From what I've read it could be the ring gear in the rear end or the RABS sensor

 

Your MMV.

I had the jumping speedo on my '93 F250. It turned out to be caused by a big chip coming off the pinion gear which in turn chipped teeth on the toner ring.

Before discovering the chipped gear and ring, I had my PSOM rebuilt (expensive) and put in a new VSS (inexpensive). I also did all of the electrical testing with an oscilloscope which took a bunch of time.

My symptoms progressed from a jumping speedo to VERY hard shifts from the tranny. The new toner ring and unfortunately a new diff fixed it all.

Best of luck with your repair.

 

Why? That is the cheapest part. About $30.00 for a PSOM at a pick-n-pull.

But as said below it might be the rear end.

 

Just for S&G, swap the cluster from your '93 into the '95 and see what it does; that should narrow it down.