See your point, we will give it a good check tomorrow.
Thanks

 

Another indication, crusie control is not working anymore. I just ordred the sensor on the speedocable unit. The gears looks just fine.

 

I meant to ask you about the cruise control, if its not working on top of everything else, then its definately in the VSS or related wiring, the iratic readings you posted about the VSS lead me to believe that you have found your problem.

 

Yes, I realy hope so too, we was promised to get the new sensor on wednesday, so we will see then.

That sensor in the rear diff, is that a VSS sensor as well? or is it just for not locking the rear breaks?
Thanks all for good valuable help.

 

On your year of truck, the rear sensor is just for ABS function, 1992 and later also uses it as an electronic speedo sensor, and eliminates the speedo cable altogether.

 

Ok David, then that one is eliminated.

 

the vss is a pulse generator it emits a/c voltage when turning thats why you had strange resistance readings , you can only check it with a hertz meter , the tr sensor wiring would have to be probed with a meter to check it , i would get it to someone that could check for codes youll spend a lot of time and money guessing

 

Is there a connector on the truck you hook up the code reader to?

 

yes , it is located in front of the left hood hinge it is usually mounted near the top of the fender , if your truck has cruise control the test connector is next to the cruise control servo on the fender

 

Ok, we will have a look for it, by the way it does have a cruise control, and after we got this trouble, it is not working anymore...

 

Snubber,

Here is one thing to check that a lot of people miss. Because your cruise control is also giving you trouble, check you brake lights. (i.e. make sure the lights go out when you come of the pedal and go on when you step on the pedal. Make sure your brake light circuit is not shorting out in any way. The reason I am saying this is that a faulty break light switch (located above the brake pedal) could send a wrong signal to both the tranny controller causing faulty shifting as well as the cruisecontrol causing it to dis-engage.

Also watch out for any shorts in your trailer wiring if you are towing a trailer. Any brake circuit problem could cause you lots of grief with the tranny as well as cruise control.

P.S. your TP checked out ok based on your readings you got. Your VSS should be ok if your speedometer is working smoothly, i.e. no sudden jumps on the needle.

A code scan is still a good thing to do. I can email you my scanner along with the manual. Send me a private email if you want to proceed with this along with your address. I helped a fellow in Finland several month ago with his 1990 F250 and it turned out that his tranny computer had an internal power problem and had to be replaced. Lets hope you are not in the same boat as a replacement is $400 new. I was lucky to locate a $200 used unit at a local wrecker here in Canada.

Give me a few days to respond as I am not always on this site.

Hope this help.


Sebastian.

 

As I mentioned earlier, a 1991 truck has a cable driven speedo, and will still give a steady reading even with a dead VSS. Bad brake light wiring has been known to cause problems with E4ODs though.

 

You are right I got a manual (non-digital) odometer in my 91' F350 so if the speedometer is also driven by the cable like the olden days then the pig-tail adaptor on the VSS would only provide a signal to the tranny computer, not the Speedometer.

I guess there is a lot of confusion about 90' and 91' trucks since they used both the sensor in the tail of the TC and the one in the Axle for ABS.

Sebastian.

 

Brake lights work ok.

 

We just changed the VSS sensor on the speedo cable unit.

Are back from the first test drive now, and so far the truck is gearing perfect...........

Thanks all