When The Speedometer Acts Up -- The Tranny gets stoned!

[sethpdx]

Ok so I have an interesting problem right now.

Sometimes my speedometer does not register the speed until it gets above 20mph then the gauge shoots up to 20 mph. the gauge is also never steady at any speed it moves…. For example I can be doing 60mph and it will move between 60mph and 65mph.
When the speedometer acts up like this the tranny is clueless about when to shift

Its also effecting the cruise control too…. If you apply the cruise control the accelerator moves up and down with the fluctuation on the gauge. It bucks around like a bronco.


My rpm, temp, fuel and batt gauge are functioning perfect.

Any ideas?
__________________

 

[sethpdx]

Anyone have any ideas?

 

[Glen4X4]

My 94 Sport did that stuff too and never did find the problem it was standard so no prob's with shifting but the guage fluctuated back and forth and cruise constantly accelerated and de-accelerated, i got tired of messin with it, could something be sticky that reads the speed?

 

[budwich]

Most likely source of your problem is the VSS sensor in / on your transmission.

 

[BrooklynBay]

Does your ABS work when this happens? Does this problem occur when the tilt steering wheel is at a certain position? I remember reading a similar thing in Gears Magazine about a lady with a Ford motor home. Her speedometer would start to go crazy at certain speeds, the transmission would change gears erratically, and the cruise control would also act up or drop out completely. She had insulation stripped off inside of her steering column from tilting it so much. She would tilt it to a certain position, and it acted up at certain speeds when the wiring would vibrate. The wire was intermittently shorting against metal inside of the column.

 

[CRUISERMEDIC]

there are a few things that i know that make this happen most likely your vehicle speed sensor or the little gears at the end of the transfer case. when mine did this it was the gears that turn the gears on the speed sensor. if you pull the sensor and look at the teeth of the gears and they are ok i would replace the sensor. of the teeth are screwed up get a new set and possibly a new sensor they are cheap enough to replace wile you are there. if its the gears i had a hard time finding them as they are discontinued. make sure you do a tooth count and make sure you get the turn right (right hand gear or left hand gear) ford used both in my year with my transfer case. i ate up a lh gear before i realised there was a difference.

steve

 

[aerostar93]

Does your ABS work when this happens? Does this problem occur when the tilt steering wheel is at a certain position? I remember reading a similar thing in Gears Magazine about a lady with a Ford motor home. Her speedometer would start to go crazy at certain speeds, the transmission would change gears erratically, and the cruise control would also act up or drop out completely. She had insulation stripped off inside of her steering column from tilting it so much. She would tilt it to a certain position, and it acted up at certain speeds when the wiring would vibrate. The wire was intermittently shorting against metal inside of the column.

I just got brakes and a brake sensor put on my 93 ford Aerostar and now the speedometer acts up above 55 mph. I'm pissed obviously. Going to take it back tomorrow for them to check it.

 

[prayforsurf0]

I had a similar problem, not sure if its exactly the same issue though. It was the rear wheel speed sensor mounted on the rear differential housing.

 

[aerostar93]

I had a similar problem, not sure if its exactly the same issue though. It was the rear wheel speed sensor mounted on the rear differential housing.

The new ABS sensor was causing the problem replaced it with old brake sensor and so far so good. Speedometer okay now.

 

[prayforsurf0]

The new ABS sensor was causing the problem replaced it with old brake sensor and so far so good. Speedometer okay now.

Good news. Yes I remember having an issue with getting this part because it seems like there is two names for this part. ABS sensor and Speed Sensor. I had to make two trips to the auto store because when I asked for one of those (cant remember what I asked for first) I got a similar, but different part. The second time I got the correct part.

I had this problem because the Haynes manual calls it a speed sensor. However, its in the ABS and Brakes section of the manual.

 

[koda2000]

On the front wheels it's an ABS sensor, on the rear axle it's both an ABS sensor and a speed sensor. The nomenclature at the parts store may call it something else, or just be confusing to the typically uneducated counter person.

 

[prayforsurf0]

On the front wheels it's an ABS sensor, on the rear axle it's both an ABS sensor and a speed sensor. The nomenclature at the parts store may call it something else, or just be confusing to the typically uneducated counter person.

Thanks for clearing that up. I was actually just consulting my Haynes to try and clear up that confusion with part names. I see now.