2004 Tacoma, A sequence of transmission misbehavior

Hello Forum friends,

I have a little story to tell about how the transmission on my 2004 Tacoma 3.4L V6 DOHC 24V 4-Speed Automatic misbehaved this past summer and I hoping some of you can help me formulate a plan to tackle its problems when I get back to the truck next summer.

First thing you should know, it's an "island truck." it resides on an island in Maine and is only used during the summer. So, it lives in a salty environment with a lot of summer fog and moisture in the air. This may be relevant as you read my tale of woe. The truck has 188,000 miles on it.

The first sign of trouble was the failure of the truck to go into 4 WD when the 4WD button on the transmission case was engaged. This was intermittent, sometimes pushing the button engage 4WD and sometimes it wouldn't. It seemed completely random but I started to believe it would engage properly when the weather was sunny and dry but who knows? The intermittency suggests to me an electrical problem going to the electronic shift actuator or some stickiness within the actuator itself. Here's a picture of the actuator. Notice the crack in the plastic housing at the bolt:


Can one of you with knowledge of this 4WD transmission case button problem suggest a sequence of steps to diagnose and address it?

The tale of my transmission woes does not end there. Later in the summer, while leaving a waterfront restaurant on an extremely foggy night, the automatic transmission itself would not shift out of 1st gear. It went into sort of a safety mode where I could drive without winding out the transmission and I made it home. The next morning I drove the truck to town and it shifted fine. The transmission continued to behave normally for several weeks (apart from the intermittency of the t-case 4WD button) until it failed to shift again on another foggy night. Does the fog have any bearing on either of my transmission problems or is a case of correlation unrelated to causation? I don't know.

With the onset of the transmission failing to shift I got myself an OBD port reader. Here's the report:


Would this read out explain the failure of the transmission to shift out of 1st gear? Again, what sequence can one of you suggest to diagnose and address the shifting problem. I've read admonishments that one shouldn't just go and replace parts based on OBD codes. Here's a picture of what I believe to be the transmission range sensor on my truck:


The last piece of the puzzle has to do with rust on the frame and comes from a mechanic who has worked on the truck before but now prefers to install septic systems. He did mine and as a courtesy he came by to look at the truck. Before he even drove down the driveway he wasn't happy with the movement of the transmission case shifter when he touched the breaks. He got out and looked under the truck and said, 'that's the source of all your transmission problems. The frame is flexing!" Here's what he saw– the rear frame section at the passenger side rear bump stock. I plan on welding a Safe T Cap kit on this next summer. Yet another issue to address. Do you think my mechanic/septic installer may be right about this being the source of my transmission problems?


Well, a long post. Thanks in advance to anyone who wants to weigh in and offer suggestions.

kmac23

 

That frame looks real rough. If its that bad there, I can't imagine its in great shape everywhere else.
I think you need to get under it and test the frame everywhere you can to make sure that its even repairable.

 

Yes time623, that part of the frame is real rough and the bump stock on the driver's side shows the beginnings of rust though much less severe. However, the rest of the frame is in good shape. The previous owner had the frame treated under the Tacoma frame rust settlement. He was a surfer though and camped on the beach in the truck which explains, I think, the rust in the rear where the wheels kicked up salty sand. I'm going to use it as an opportunity to buy a MIG welder.

I found good information on how to look into into my actuator problem here:
https://www.tacomaworld.com/threads/how-to-trouble-shoot-4x4-actuator.263525/
and here:
https://www.tacomaworld.com/threads/4x4-issues-front-diff-actuator-or-t-case-actuator.358059/
These via Discussion in 'Technical Chat' started by gearcruncher, Sep 24, 2014 here:
https://www.tacomaworld.com/threads/transfer-case-transfer-cases-in-first-and-2nd-gen-trucks.345652/

I'm thinking gearcruncher or Dm93 or somebody else must have posted good links for my 1st generation transmission failure to shift problem and the PO705 code. Anybody have a clue where to look?

THanks,
kmac23

 

It probably wouldnt hurt to start by checking the transmission range sensor ( Nuetral safety switch ) for wiring issues . I think if you start messing with the neutral safety switch , you are going to run into trouble with corroded wiring .
This should take care of the transmission shifting issue . Its a place to start in an effort to get the code to clear .

Are both problems related to the same thing ? This is very possible .

 

It would almost seem like your shifting linkage was between two gears (D and N?) ... Don't know how likely or possible that is though

 

Thank you gearcruncher for offering a common sense place to start. No need to start pulling parts off the truck needlessly, right? The intermittency of both my problems does seem to point to the wiring as the source. In your experience have you found that minor corrosion in the connector can be addressed with fine emery cloth or a small file? Your suggestion that the shifting problem and the 4WD actuator problem might be related and caused by corroded wiring to the neutral safety switch is also intriguing. I'm really eager get back up to Maine and pull the connector off the top of this guy and see whaat I find. I'll certain post the results.