I have a 93 F-150 with a 300-6 and 5-speed manual transmission.
The speedometer works fine until 50mph then starts jumping all around.
The cruise control won't work because of this.
Anybody have an idea what the problem might be? Instrument cluster, speed sensor pickup??????

Dave

 

It's the speed sensor. I had the EXACT same problem about two weeks ago. But mine also had very firm 1-2 shifts. Unfortunately, I can't tell you where's the speed sensor on your '93 F150. But on mine I had one on the rear diff. pumpkin, two on top of the trans. and one on each front wheel. Mine was on top of the tranny and it was a mother to get to. Good luck.

 

Flyingman, I believe your truck has the cable and gear set-up instead of the sensor's of the '99. If so, my experience w/my ol' '88 may help. Had a similar problem - erratic speedo that eventually stopped working entirely. Changed the cable from the speedo to the tranny(or xfer case on 4x4) just because it turned a little stiff and was several years old. Either way the cable should go into the rear of the appropriate case on the driver's side just in front of the drive shaft. On mine it is held into the case with a small bracket/clip held in place with a bolt. Also changed the gear on the end of the cable which looked chewed up a little. Everything worked ok again for about a year. Then the whole thing started again and stopped working again. At that time the cable still turned easily but the little gear looked BAD. There is a matching gear in the tranny or xfer case. This turned out to be the real culprit on mine. Without more knowledge at this point I'd recommend consulting a repair manual for how to get to this gear if it turns out to be your problem.

BTW I was able to get a look into the hole in my xfer case to see the condition of the inner gear. You may be able to do likewise.

Also, if you change the cable like I did Be Sure you notice Exactly the route the cable is run thru the dash as they will bind and you'll probably get to buy another one. Guess how I know?

 

My guess is you have a broken speedo cable... twists ok at slower speeds... begins to miss then catch at higher speeds.

 

Thanks for the replys all.

I have the sensor in the rear diff. I think that's where my problem is. But don't quite understand why it would be intermitten since it's a solidstate unit.
I just don't want to do the shotgun approach and waste a lot of money I don't have.
I am also curious whether the speedo could cause my problems.

Thanks

Dave
Dallas

 

I believe you will find the sensor in the rear diff. is for the anti-lock brakes. I think you probably have a cable and gear set-up from the rear of your tranny to the speedo. I don't believe Ford trucks went to electrical sensors for the speedo until '98 or '99.

Also let me suggest you post your question in the pre '97 forum. Probably more expertise on your truck to be found there.