just bought this nice 159 k ext cab truck and e4od tranny hard shifts more times then not. took to tranny tech and he changed the speed sensor on rear diff. this cured the hard shifting for only 30 min. of driving time, then started again, hard. Also, now the speedo needle jumps and flickers when going btwn 50 and 60 mph.

it did not jump around before. I took it to another ASE mechanic and he put computer on and had no codes. he also printed out schematic and said the speed sensor on rear diff has to send signal to the speedo, on wire c7, then the signal is sent out of speedo to the ECM.

the cruise control doesn't work either. He said he will check the instrument console for the correct output to the ECM. He said if it is correct, he would change the ECM. the instrument cluster is $125-150 from a yard and the ECM is $75-95. weird as this sounds, we just moved our Daughter and when the truck was loaded down with furniture the truck shifted perfect. As soon as was empty, it did it immediately. honest.

It will cost another 235 dollars to change the instrument cluster, and I think it still could be the wiring from the rear unit after all. my question/request is to ask if there is anything I can do myself to shoot this trouble and see if it fixes it?

thanks Silvermax16

 

Many aftermarket VSS sensor are inferior and cause the exact symptom you are experiencing since the replacement (jumping speedo). Go back to that "mechanic" to see if they installed a Motorcraft/Ford part. If not, make them do it.

Did any of these "mechanics" actually measure the VSS signal at the PSOM? They sound more like parts replacers to me.

The VSS signal goes to the RABS control module before it continues onto the PSOM, The output of that goes to the computer (PCM) and Speed Control module. It's not uncommon to have the RABS module or Speed Control "drag" the signal down. It's a process of elimination. Unplug the Speed Control module for a while, see if the hard shifts go away. If not, plug it back in then do the same with the RABS module (located behind the glove box).

Meanwhile you now have an inferior VSS to deal with...

A great diagram and procedure to check the VSS signal output from Steve83: http://www.supermotors.net/registry/media/95932_1

 

Yes do what rla2005 said above.
If the free unplugging does not tell you have a bad module (speed control or ABS) then I would say you have a problem in the rear end or a loose wire under the truck. More than likely the rear end tone ring has a bad gap space from bad bearings in the rear end.





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The instrument cluster should not cost more than $30.00 at any pick-an-pull.
If the PSOM is bad in your cluster just swap the whole speedometer head, odometer and PSOM out as one unit to your cluster. It takes less then a half hour to swap them out from cluster to cluster.
The cluster only takes about an hour or less to change out in the truck and you can do that yourself.

If you want to keep your mileage any computer hacker can copy you old mileage over and set the change number to 6.

 

My personal experience with the hard shifting was having to have the solenoids changed in the trans. I took the truck to Ford and they put a breakout box on it, they changed the VSS first and that lasted about 1 day. By time I got done, Ford had charged me just under $900 to fix the problem.