I assume I am doing this right? I was hoping somebody might be able to help me with a problem I have on my 95 F-150 w/ a 4R70W transmission. I am having problems with the transmission (usually at 35-70mph) coming in and out of gear. Sometimes the OD light comes on and off sometimes it doesn't. Sometimes the check engine light comes on. I haven't been able to do something to make it happen...it just does it unpredicatably. I have had all the electronics checked out on the transmission by a shop and they found nothing. I have run diagnostics on the engine and the only codes I have gotten are a result of engine modifications I have done (no smog pump, etc). I do have a shift kit and 2800 stall converter in the transmission but they have been working fine for over 40K miles. Transmission shop is reliable and they say it is not the transmission. I replaced the Throtte position sensor/TPS (it was faulty) and the sensor on the side of the transmission that tells the computer what gear you're in (can't recall the name of that sensor off the top of my head).

The only thing I can do (that often temporarily "fixes" the problem) is turn the truck off completely and then start it back up.

Any suggestions? Folks w/ a similar problem?

Thanks, Nick

 

I would want to be sure of what you mean by jumping out of gear.
Does that mean the engine races then catches again?
The trans is shift controlled by the computer.
Putting it in and out of a drive gear is done manuelly.
Does it happen in lower gears etc? All important as it is difficult as it is to get a lead on.
These things have to be zeroed in on at to how it is happening.
If there is an OD light and/or an Cel lamp at times then the problem is intermittant.
You can't find something that is not there when you look for it.

 

This is the best I can describe it. You will be driving along normally and IN ANY GEAR (although usually in 3rd and up) it will feel like the tranny is slipping. The motor doesn't rev on it's own but, if you give it gas, it revs up AND DOES NOT catch a gear. Tranny seems to be trying to "decide" what gear it wants to go into w/ out every really picking one and sticking to it. Sometimes the OD light will flash for a few seconds and then stay on. Sometimes the check engine light will come on and stay on. When this happens I usually have to stop the truck, turn it off, and reset the computer. Once that is done it seems to drive normally again for a while. I read that the TPS has caused this on other vehicles so I checked mine and noticed a short in the wiring (exposed wires at the sensor). I replaced that and it seemed to work good for a while but now is doing it again. I took the truck into a tranny shop and they dropped the pan, checked out the tranny, and assured me that it was most likely not the transmission. Here are some thoughts that I have:

1. I have heard the speed sensor can casue this kind of problem. I don't notice any irregularities in the speedometer though. Can the speed sensor be bad and NOT AFFECT THE SPEEDOMETER?

2. Perhaps the trucks main computer is bad? I did not get any significant codes on multiple tests (including engine running) but maybe it is faulty anyways?

Thanks for the reply, any thoughts?

Nick

 

The only thing I get for sure, is the flashing OD lamp is telling that the trans has a problem and that the PCM also displays the fault by the CEL lamp.
You have two ways to go.
1. Guess and spend time and money and maybe have a little luck.
2. Trap the code/s so you know what malfunction is happening and go right to the fault and have it over with.

There are a lot of things that could cause the problem. By guessing, it's take your pick.
Since you see the failure long enough when driving, your at least lucky to that extent.
Arrange to have someone go with you that can read the code or drive right to the shop so they can read them without turning off the engine.
IMO, it's either do it this way of live with it till it breaks.
Some of the possible faults are the speed sensor has a noisey/intermittant output, torque converter clutch, EPC solenoid that controls main pressure etc.
IMO a faulty TPS would not only affect the trans shifts but also how the engine runs.
Good luck.

 

Go to Autozone and get a neutral safety switch for your vehicle. Make sure that you install it with the transmission in neutral and just line up the marks on it that say neutral and make sure they are still aligned after you tighten down the 2 8mm bolts that hold it in place. If its not adjusted that way you will have a different problem.

Now, this is not just a neutral safety switch. It is known by Ford as an MLPS. This sensor tells the computer what gear the transmission is supposed to be in.

They fail. A lot. When they do, this is usually what happens.

Darrin

 

Darrin/ Blue grass

Thanks for the info guys, I will borrow a code reader to try and get it when it happens and not turn off the engine.

You are right on the neutral safety switch....the tranny shop had suggested the same thing and I already changed it out (prior to the TPS). Thanks though.

Take care, Nick

 

I hate say this but my gmc does the same thing and know the trans is completly shot.

 

you ever get this thing fixed?

 

Ever get this fixed - mine has same issue