I have a 1997 F-150 with an automatic transmission. The speedometer has recently started acting up. The needle starts bouncing after two or three miles and the transmission will shift up and down way too much. If I put it in first or second the shifting stops and I can continue on at a slower speed.

I replaced the speed sensor on the transmission tail shaft but that didn’t change anything.

What else should I look at?

 

Have you checked the OBD codes yet? If not, you should. This might help you figure out what is wrong. I've got a suspicion that it might be a bad solenoid or internal pressure problem. Spring?

 

Did you check the gear that attaches to your sensor on the trans tailshaft on the driver side. The teeth on mine got chewed up and caused all kinds of havoc.

 

I haven’t checked the codes yet. I’ll get that done this AM.

 

Yes. The teeth on the plastic gear are fine.

 

`97-98 and early Super Duties all use this cluster with analog odometer. The gear inside the cluster (speedometer) do wear out and can cause the jumping you are experiencing also. I'm not sure that this will cause the transmission shift problem, but the PCM is most likely monitoring the speed (should be done thru the tailshaft sensor) but I haven't checked the wiring schematic to see for sure. You can buy the gear kits on eBay to replace yours if they are damaged. Just another thought.

 

I had the codes checked. It showed two codes.
P0501 Vehicle speed sensor, range or performance problem.
P0503 Vehicle speed sensor circuit, Intermittent, erratic or high input.