Questions and Answers

Ford Bronco Shifting Problems Q. I have a 1992 Ford Bronco (full size with a 351 V-8, automatic transmission, and it has 120,000 miles. It has fuel injection, rear ABS, and AC. Here is the problem I am having: My Bronco has been having issue shifting (automatic). It seems to be sluggish in shifting and deciding what gear is best.

Sometimes it lugs the engine for a while before it finally downshifts, and other times it shifts okay. Took it to a transmission shop and they said the transmission is fine and they also checked the computer, no codes.

However, they did find that when they connected to the speed sensor they did not get any data. So they replaced the speed sensor and it still was not sending information. They said I should take it to an electrical automotive specialty shop.

So I did and this man diagnosed the problem to be a faulty instrument cluster. Would a faulty instrument cluster cause this kind of problem? The transmission people say that the transmission is confused because it does not know how fast the vehicle is going and therefore does not know when to shift.

Thanks for looking at my question.
Alan

A. This is a Ford, and with a Ford all things are possible.

This is how the system works. The Programmable Speedometer/Odometer Module (PSOM) 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 speed signal output is proportional to the road speed of the vehicle.

The Programmable Speedometer/Odometer Module supplies this signal to all components that require vehicle speed information Including the Speed Control Amplifier, the Transmission Electronic Control Assembly (TECA) (with diesel engine), and the Electronic Engine Control (EEC) Module (with gasoline engine).

So it is possible for the PSOM to get a good signal and yet not send it out to one, or more, of the other speed signal users. If this is what they meant by a faulty cluster, then they are correct.