bouncing speedo ......
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Joined: Mar 2014
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bouncing speedo ......
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
. 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
Mountain Pass
Joined: Jul 2014
Posts: 244
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From: Minneapolis & Terlingua
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.
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.
Fleet Owner
Joined: Aug 2005
Posts: 23,667
Likes: 301
From: Easton,Ks
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.
But as said below it might be the rear end.
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