1992 Bronco is Hard Shifting

[fburrowatl]

I have a 1992 Bronco that I recently purchased. It ran so good, I felt I bought a great machine!! However, it was a little too good to be true.
I was driving it and all of a sudden it started shifting REALLY hard. It was SO hard that I literally thought the transmission was going to fall off the car. It did this for several miles and then it simply stopped doing it. It took about another 150 miles and it did it again. This time it threw a code (cannot recall what it was) but it pointed me to the TPS. I replaced it and still didn't work. After this, it happens MUCH more frequently and I cannot figure out what could be causing this. We replaced the TPS sensor and also the sensor located next to the transmission itself (can't remember its name), the fuel filter, and we flushed the transmission and replaced the fluid and filter. THE STRANGEST PART is that if you manually shift the car, there are no issues; it shifts smooth as silk. Has anyone heard of this every happening and how I could possibly fix it?? I hope I explained it well.

 

[Jimbo26]

...'sensor located next to the transmission itself..'-
The MLP/range sensor on the shifter shaft?

E4OD or 4R70W?

 

[Tiha]

If it is shifting hard there are codes stored somewhere it would help to know what those are.

Common things, How is your speedometer? Does it bounce?
All your brake lights work correctly, including 3rd brake light?
The wire harness where it enters the transmission is pretty close to the exhaust. Could be heat related, also that harness plugs into the trans, the plug collects water, oil, dirt and can corrode creating bad connection.

Then codes might point to something else like a bad solenoid inside the trans.

 

[miesk5]

Yo fburrowatl,
Welcome!
As advised and try your Test for Diagnostic Trouble Codes again and post the code(s) here or do this self test by my pal, BroncoJoe19 @ Code Reader.....
●
PCM stores the Self-Test program in permanent memory. When activated, Self-Test checks the EEC system by testing memory integrity and processing capability, and verifies that various sensors and actuators are connected and operating properly.

Some possible perpetrators are;

Powertrain Control System​	​
Electrical inputs/outputs, vehicle wiring harnesses,powertrain control module, throttle position sensor, vehicle speed sensor, electronic pressure control

■
Here's the 1992 Bronco Dealer Brochure @ http://www.auto-brochures.com/makes/Ford/Bronco/Ford_US Bronco_1992.pdf

Haynes Red Manual for 80-95 Bronco & F Series @ Hanes guide 80-96 bko f series.pdf via BroncMom!

See my mostly recovered View attachment 202203
site by schwim @ Ford Bronco And F-150 Links - FORD BRONCO

Al

 

[fburrowatl]

If it is shifting hard there are codes stored somewhere it would help to know what those are.

Common things, How is your speedometer? Does it bounce?
All your brake lights work correctly, including 3rd brake light?
The wire harness where it enters the transmission is pretty close to the exhaust. Could be heat related, also that harness plugs into the trans, the plug collects water, oil, dirt and can corrode creating bad connection.

Then codes might point to something else like a bad solenoid inside the trans.

So, we took it to a mechanic who supposedly knew what was what. He said it was ready. We drove it out and then it hard shifted REALLY bad. Took it back to him and he told me the new TPS sensor is broken and just spinning. So we are having him replace that again. However, the good news is that it threw new codes (5 of them) so hopefully we can figure this out! I will DEFINETELY look into the wire harness, however. Since the problem is so intermittent, maybe that is what could be causing it. The speedometer? Curious how that is related. I ask as we do have a bad gas gauge and I worry about other issues with the instrument panel; but it does not bounce. 3rd brake light... I cannot recall but I will check it.

 

[fburrowatl]

Yo fburrowatl,
Welcome!
As advised and try your Test for Diagnostic Trouble Codes again and post the code(s) here or do this self test by my pal, BroncoJoe19 @ Code Reader.....
●
PCM stores the Self-Test program in permanent memory. When activated, Self-Test checks the EEC system by testing memory integrity and processing capability, and verifies that various sensors and actuators are connected and operating properly.

Some possible perpetrators are;

Powertrain Control System​	​
Electrical inputs/outputs, vehicle wiring harnesses,powertrain control module, throttle position sensor, vehicle speed sensor, electronic pressure control

■
Here's the 1992 Bronco Dealer Brochure @ http://www.auto-brochures.com/makes/Ford/Bronco/Ford_US Bronco_1992.pdf

Haynes Red Manual for 80-95 Bronco & F Series @ Hanes guide 80-96 bko f series.pdf via BroncMom!

See my mostly recovered View attachment 202203
site by schwim @ Ford Bronco And F-150 Links - FORD BRONCO

Al

Great stuff!! Thank you!!

 

[Tiha]

So, we took it to a mechanic who supposedly knew what was what. He said it was ready. We drove it out and then it hard shifted REALLY bad. Took it back to him and he told me the new TPS sensor is broken and just spinning. So we are having him replace that again. However, the good news is that it threw new codes (5 of them) so hopefully we can figure this out! I will DEFINETELY look into the wire harness, however. Since the problem is so intermittent, maybe that is what could be causing it. The speedometer? Curious how that is related. I ask as we do have a bad gas gauge and I worry about other issues with the instrument panel; but it does not bounce. 3rd brake light... I cannot recall but I will check it.

Still assuming this is an E4OD. The speedometer/dash uses what is called a PSOM that takes the VSS signal from the rear end, runs the speedometer but also send the signal to the ECM so it knows when to shift and not shift.

TPS can certainly affect the shifting if it is bad and replacement parts are usually out of spec right out of the box. It can be an adventure keeping these trucks running properly.

A fault in any of these or a dozen other systems causes the ECM to put the trans into limp mode which means harsh shifting. It raises line pressure to protect the transmission and that gives you head snapping shifts.