Transmission Problem? or Engine?

[RammaR]

I've done several searches and have found a few simliar problems but not an exact match so I thought I'd go ahead and ask.

Over labor day we took the Explorer on a 7 hour trip back home to visit some family. While driving on the interstate it felt like it would slip out of overdive. Only happened a couple times on the drive in - mostly while doing about 75. I could feel it rev a bit like going back to drive and then it would drop back into OD.

On the way back home, it started getting more and more frequent and worse. About 4 hours from the house it did it several times in a row and the O/D Off light started to flash - so we immediately pulled over to a gas station. I wanted to check the fluid level again, etc. The fluid level is just a little high. The battery had been acting a little weak and when I started it back up it took a couple times to crank over. When it did all the radio presets were gone - like the battery had been disconnected. But now the O/D off light was cleared as well. We got back on the road and it continued to "slip" in and out of OD for a little while but the error light never returned. I turned O/D off and it drove perfectly the rest of the way home and had the battery changed out the next day. Maybe I shouldn't have but it seemed like the O/D off code was lost with the radio presets anyhow.

So then I took it to a local transmission shop that had been recommended. They could feel the "slipping" but there were no stored codes. Their opinon was that the transmisson appeared to be functioning normally and that it might be comptuer or sensor error that was sending bad info and making it fault on changing gears. They said keep driving for a while and see if it throws the O/D light again or else take it to my normal mechanic.

After driving all last week tyring to get the O/D light to return - it never did. But last night on my way home the CEL light came on. I hope to have the code pulled tonight - but am at a loss as to what it might be. The engine runs great and besides this "slipping" in and out of O/D its near perfect.

Could a bad torque converter lock-up solenoid throw a CEL code? Any other suggestions on what to look for?

Sorry for the long story but didn't want to leave out any details. Thanks.

 

[Alec]

I'd guess the CEL code is gonna be due to the TPS, throttle position sensor.

 

[RammaR]

Do you think that's a by-product of the surging or part of the root cause?

 

[Alec]

The TPS has involvement in everything from timing, fuel delivery, to tranny shifting.

The problem may be easier to solve once you get the code read.

 

[TPLYNCH]

You sure it was shifting out of O/D and not the torque converter locking/unlocking? Either way, whatever happened may have overheated the tranny and that may have caused the flashing light. Just out of curiosity, were you or have you tried using cruise control? Besides the TPS, a fault with your Alternator can cause problems with the tranny too. Have that tested, especially if the battery was straining when you were trying to restart.

 

[RammaR]

Well - from my undstanding the real difference between Drive and Over Drive is that the torque converter is fully locked in OD? It feels like its "slipping" in and out of OD - so this could just be the lockup engaging and disengaging?

The transmisison shop suggested the O/D flash was due to a high temp - party because it hadn't returned after shorter drives while experiencing the same issue.

When I had the battery changed out I asked about he alternator and they showed me this clamp on tester that said it was ok. But I will say that it was raining, so lights (included piaa driving), wipers, A/C and radio (stock) were on - so it might have been a heavy drain on the alternator. Worth double checking maybe?

 

[Fhantazm]

From the sound of it, it definitely sounds electrical. Especially if you were having starting problems, as well as loosing the radio presets. I had a similar problem with one of my other cars. The interior lights didnt work, and the xmission would stay in "limp" mode. Turns out there was an electrical problem where a wire eventaully burnt in two.

 

[RammaR]

Ok, heres a quick update. Wasn't able to meet up with code last night to pull the CEL code. But on the way home from work tonight the O/D Off light started to flash again. We did pull the code and its:

P0761: Shift Solenoid C Per For on stuck off

Is this the torque converter lock-up solenoid? I guess I'm off to the transmission shop in the morning - but does anyone have any idea what to expect? Do you have to pull the transmission to service it?

That was the only code stored, so I'm hoping it will be a fairly simple fix and not involve a full rebuild.

Thanks in advance for any tips.

 

[RammaR]

Well another update. After just a little more driving - actually driving it to the transmission shop - I effectively have no overdrive. You can hit the O/D Off button and the light comes on and the rpms will blip for just a second and then settles right back down as if in 3rd gear. Other shifts are starting to feel a little weak as well.

The tranny guys pulled the same shift solenoid code and another gear ratio error code. They are saying that something mechanical in the transmission is failing and that the solenoid is probably working - but since the computer doesn't see the expected change in speed/rpms for OD it defaults to saying that the shift solenoind is off. Another part of the problem with it might it failing to "lock-up" properly. Their recommendation was to rebuild the transmission and relpace all of its internal electroics.

Their explaination after driving it with me seems to make sense. And the problem has gotten much worse in the last 48 hours. But I'm not an expert, does anyone here have an opinion?

 

[jobunn]

Originally posted by RammaR
Well another update. After just a little more driving - actually driving it to the transmission shop - I effectively have no overdrive. You can hit the O/D Off button and the light comes on and the rpms will blip for just a second and then settles right back down as if in 3rd gear.


There doesn't seem to be a doubt that there is something wrong with the tranny but explain this above in more detail.

If you are traveling at a high enough speed (around 50 mph) and in O/D and you turn the O/D off (light on) it will kick into 4th gear (rpm's go up), and often if the tranny thinks it's time, will either immediately or shortly after also lock the torque converter in 4th gear (rpm's settle down). This is what it sounds like is happening in the above description.

Well - from my undstanding the real difference between Drive and Over Drive is that the torque converter is fully locked in OD? It feels like its "slipping" in and out of OD - so this could just be the lockup engaging and disengaging?

The torque converter can be locked in Drive or Overdrive. And the tranny will continue to lock or unlock the torque converter (could be mistaked for slipping) based on your use of the throttle and road conditions (uphill, downhill etc)

 

[jobunn]

I just realized we don't have the same tranny but the principal still applies. Your 4th is just my 5th and so on.