1997 F150 transmission issue

[deerefan]

I have asked a lot of questions here about this truck and have received great feedback. Here recently, the od light had started blinking and the trans seems to be "downshifting" and "upshifting" in overdrive. Engine rpms jump from 1600 to 2000 and back again every 15 seconds or so. I also noticed the speedo indicator is a little jumpy. It feels like the tourqe converter is locking then unlocking continuosly. Any thoughts? The truck is 4wd, 4.6 V8.

 

[Peacock]

I have asked a lot of questions here about this truck and have received great feedback. Here recently, the od light had started blinking and the trans seems to be "downshifting" and "upshifting" in overdrive. Engine rpms jump from 1600 to 2000 and back again every 15 seconds or so. I also noticed the speedo indicator is a little jumpy. It feels like the tourqe converter is locking then unlocking continuosly. Any thoughts? The truck is 4wd, 4.6 V8.

Gonna have to get it scanned and see what the code is. Anything before that would be a guess.

Autozone will pull codes for free.

 

[deerefan]

Gonna have to get it scanned and see what the code is. Anything before that would be a guess.

Autozone will pull codes for free.

Apologies. Did this already- nothing showed.

 

[Peacock]

That's odd. Does the speedo jump while the od light flashes? If so, I'd be very suspicious of the VSS in the rear diff.

Generally generates a P0500 code.

Sometimes the wires break at or near the connector. Also take a good look see at the terminals. Have seen them get corroded and loose continuity.

 

[deerefan]

That's odd. Does the speedo jump while the od light flashes? If so, I'd be very suspicious of the VSS in the rear diff.

Generally generates a P0500 code.

Sometimes the wires break at or near the connector. Also take a good look see at the terminals. Have seen them get corroded and loose continuity.

Yes it jumps, kind of "shakes".

 

[Peacock]

Yes it jumps, kind of "shakes".

Take a good look at the 2 pin connector on top of the rear diff.

If it looks fine I'd just put a VSS in it if it were mine. Used to be real cheap. Get it from the dealer if you can.

 

[Diamondpilot]

I would take it to a trans shop for a scan. More than likely its a sensor or valve going or a broken wire as Peacock stated.

Chris

 

[deerefan]

Take a good look at the 2 pin connector on top of the rear diff.

If it looks fine I'd just put a VSS in it if it were mine. Used to be real cheap. Get it from the dealer if you can.

Found the sensor, unplugged it and blew it out. How hard is it to swap out? Looks pretty easy.

 

[Peacock]

Found the sensor, unplugged it and blew it out. How hard is it to swap out? Looks pretty easy.

Easy. 1 bolt. Thinks it's an 11mm.

Look at the terminals real close with a bright light.

 

[deerefan]

Easy. 1 bolt. Thinks it's an 11mm.

Look at the terminals real close with a bright light.

Found the part, $38.69 at Ford. Will change today and report back. Would this sensor cause the trans to shift like described above?

 

[Peacock]

Very well could.

The VSS input is used for a multitude of transmission controls. From EPC solenoid duty cycle to TCC valve duty cycle to shift solenoid managing.

 

[deerefan]

Very well could.

The VSS input is used for a multitude of transmission controls. From EPC solenoid duty cycle to TCC valve duty cycle to shift solenoid managing.

The erratic shifting started when light started blinking, so hopefully this is it. Thanks for all the help!

 

[deerefan]

Well darn. The needle still twitchy, shifting weird and the o/d light is blinking still. Is there a speed sensor on the trans tail shaft?

 

[sld]

If no code is showing, or if it was and you read it, disconnect both battery terminals and give them a good cleaning.

It's a good thing to do and it will reset your system. If the issue still persists, it has to be storing a code.

The VSS's do go bad so it was a good thing to replace anyway. Reset your system and see what happens next.

 

[Soundguy]

does that model have a GEM module?

the gem in my 99350 got wet from a leaky canopy lamp base.. and gave me a twitchy rpm needle and blinking od lamp

 

[allen6634]

the frist thing i would check is the speed-o sensor, i would think the tranny is comp. controlled, if it is't getting the right info about the truck speed, then it will go nuts

 

[94BULLITT]

Take it to a repeatable shop and have them scan it. Those clowns at the parts stores don't know what they are doing.

 

[geblackwell]

Had a 1997 f150 that did the same thing after it had 100,000 miles on it. At that time the shop that worked on mine said this was common. Their solution was change the fluid and put in some type of additive. This worked for several thousand miles, but was starting to return when I traded it.

 

[Soundguy]

that sounded like a slip.. and they put in a friction modified fluid.

not sure this si the same issue with a blinking OD lamp...

 

[rsallen]

Speedo/instrument cluster?
Possible ECM.

Be sure to check all the others, wiring, sensors etc.