Vehicle will not Move forward, is it the transmission or could it be something else?

Tiny
SHAROLTHEQUEEN
  • MEMBER
  • 1999 FORD EXPEDITION
  • 5.4L
  • V8
  • 4WD
  • AUTOMATIC
  • 307,000 MILES
I was driving along and "Pop!" Then rough sputtering, and I knew the lovely Triton had spit out another spark plug (3rd or 4th time it has done that). Towed it to a nearby friend's house and parked it. Next morning, I re-threaded the hole, replaced the coil pack and plug, and was on my way down the road to work. At a stop light, when I stepped on the gas to go, the transmission seemed to slip a little. The more I drove the more it was slipping. I stopped, checked the transmission fluid. It was a little low, so I added a little fluid. I put it into drive, and it would not move forward. Tried switching it into 4WD low and high wouldn't move forward, same when I took it out of 4wd. It would only go backward, so I had to drive it in reverse around my apartment parking lot and finally got it parked in my very narrow garage (took a lot of pushing forward then driving in reverse and repeat). I had not had any problem with the transmission before this.

Could it be something other than the transmission? Maybe I knocked some wires to the MAF or TPS or some other sensor loose that directly affects the TCM? I just cannot afford to replace the tranny right now and I desperately need a vehicle for work. I am hoping and praying that it might be something other than the transmission itself. What should I check? Also, on the gear shifter inside, someone broke off the tip and I had to rig the O/D button wires and attached the tip back on the shift lever with electrical tape. Could that be contributing to the problem? No check engine light on.
Wednesday, September 27th, 2023 AT 2:58 PM

5 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,700 POSTS
Hi,

If you have no forward gears, the switch isn't the cause. I have a question. Does the gear indicator indicate the correct gear selection? There could be an issue with the transmission range sensor.

On the other hand, we may have lost transmission line pressure due to something such as a partially plugged transmission cooler.

What you described doesn't sound like the transmission itself has failed. It sounds like we lost the pressure needed to engage forward gears. Will it move forward if you put it in low 1 or first gear?

Let me know. Also, if you look at pics 1-3 below, it indicates possible causes of no forward gears. The remaining pictures are the directions for testing line pressure. Let me know if that is something you are comfortable doing.

Take care,

Joe

See pics below.
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Wednesday, September 27th, 2023 AT 9:12 PM
Tiny
SHAROLTHEQUEEN
  • MEMBER
  • 3 POSTS
Hi Joe,

Thanks for your reply! I appreciate any and all help! I am broke and cheap, so I at least try to do as much work on my vehicle as I am physically able to do. A lot of times that means I'm learning as I go. I have never needed to do anything with a transmission other than check and fill the fluid levels. Therefore, I am a tranny-virgin, so to speak. But Mi willing to learn!

* The gear indicator does indicate the correct gear. I checked the linkage under the steering column and that was a little loose, so I tightened it. I don't know what to check underneath the vehicle, and I don't know what it means to "verify the TR sensor is properly adjusted".

*No, it will not move forward in low1 or first gear (nor in low or high 4wd).

As far as testing the line for pressure, I am not opposed to trying it but I might need some hand holding or a YouTube video to watch how to do that. Is the tap for the line on the outside of the bellhousing or do I have to get up in there to access the line and the filters? Also, what kind of pressure gauge do I need, and can I borrow one from O'Reilly's or Auto Zone?
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Thursday, September 28th, 2023 AT 10:43 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,700 POSTS
Hi,

For now, skip the pressure testing. If you are not seeing the gear indicator light up, there is likely an issue with the transmission range sensor.

The first thing to do is confirm there are no issues with the wiring and connector. The TR sensor is located on the side of the transmission and a manual shift cable attaches to it.

I attached the directions below for replacing it so you can see the steps for adjustment (if needed). Adjustment does require a specialized tool. However, if there is no light indicator, we need to confirm the wiring is okay.

Let me know what you find or if you have other questions.

Take care,

Joe

See pics below.
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Friday, September 29th, 2023 AT 9:42 PM
Tiny
SHAROLTHEQUEEN
  • MEMBER
  • 3 POSTS
Hi Joe!

Sorry it's been a while since I've had time to email. Okay, I did get under my Expedition and checked the alignment of the Transmission Range Sensor. In neutral, it was a little bit off, so I adjusted it a little in order to line up the two marks. Also, I re-attached the "overdrive" button that had broken off the end of the gear shifter (why would somebody put it right there at the end of the shifter? Duh!). So now that indicator light turns on/off when the o/d button is pushed.

Started up the truck, shifted. Still, the only gear that moved the wheels was reversed. No check engine light coming on. Are there other things I could check-out? Sensors that affect the TCM? Is there a way to re-set the Transmission Control Modulator? I've seen a couple of different ways to do it online, but none of them have worked on my vehicle.
Any suggestions for what to check next, and how to check? I'm very appreciative for any all of your help!

Thanks,
Sharol
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Wednesday, October 11th, 2023 AT 12:31 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,700 POSTS
Hi,

It would be a good time to check the line pressure. If it is low, that would cause this as well.

If you look below, I attached the directions and specifications for testing transmission line pressure. Take a look through them and let me know if you are comfortable performing them.

Take care,

Joe

See pics below.
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Wednesday, October 11th, 2023 AT 7:23 PM

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