DizzyD

Hi all! my '93 F250 is a farm truck, 351 EFI, 4X4, auto trans, used primarily for snow plowing. I don't let it sit all summer long without driving it up and down our dead end street at least once every 2 weeks to keep parts lubed, batt charged and the juices flowing. I took it for a ride last week and to my surprise first to second gear was a very hard shift with a big clunk. So I pressed on and second to third same thing, third to 4th was better. Slowing down it does the same as it downshifts. First thing I checked was fluid level once it was warmed up. It's right where it should be (installed new trans fluid, pan gasket and filter last spring). So based on a similar, past experience with my previous truck (1985 F-350 non-EFI) I went below and looked around for the trans vacuum module hoping it had failed, or mabe a leak in the line. This truck has neither, so now I'm wondering what could be causing the hard shifting? One last critical piece of information, last night I noticed the speedometer is not working. Am I going to be looking for a bad sensor / electrical / computer problem?
I don't have plates or insurance on this truck as it never goes on the road so a trip to the local parts place or dealer to plug it in for analysis is not an option.
Any suggestions, tips and observations are greatly appreciated.... the snow is only a matter of weeks away now!

Bert

It could be the speed sensor causing that. It's mounted in the top of the differential and often gets metal particals on it. Clean that off and see if it helps.

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Bert

DizzyD

I yanked the sensor and it's clean as can be. Gonna see if NAPA has replacements or it will be off to the dealer. BTW, I found a perfect sized plastic plug to fit in the opening to keep moisture and mice out. took it for a ride with the sensor out and it is acting the same way so I'm hoping a new sensor will fix, if not I'm not sure what to look at next.

DizzyD

Bert, new VSS installed and still no speed-o and still rough shifting. are there any other sensors I should be looking for or connetion points that may have failed?

Bert

There's a component in the speedo that picks up the signal from the VSS. What transmission is it? AOD, C6, or E4OD.

From the Ford manual. For the speedo.

The Programmable Speedometer/Odometer Module includes the Speedometer, the Odometer, and the Trip Odometer, all of which are electronically controlled by a programmable integrated microprocessor. The microprocessor receives a speed signal input from the Differential Speed Sensor (DSS), and uses a programmed conversion constant to convert the signal to the standard 8000 pulses per mile speed signal output. The Programmable Speedometer/Odometer Module is serviceable only as a unit. It is important to keep the Speedometer face-up since speedometer function will be affected by storage in the face-down position.

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Bert