Transfer Case Actuator??

Sooo... A while back, I had to make an emergency shift into 4x4 during a period of high wheel spin to avoid getting T-boned. MY 06 TRD Sport (138,xxx) made the shift with a bone jarring THUNK that made me cringe....A few weeks later (just as it was getting snowy) my 4WD indicator began to only blink and not become solid. I could tell the truck was in 4x4 based on the wheel bind, but the dash indicator would not become solid. It would still shift to 2wd and the indicator would disappear from the dash like normal.

Two weeks later, the rig will no longer shift into 4x4 while moving. The only way I can coax it into gear is in the "on" setting of the key, where the dash lights are illuminated, but the engine isn't running.

Now, the rig is in 4x4 and basically stuck there. (this is good because I live at 8500' in the High Rockies. we got 28" in the last 48 hours) It takes a bunch of effort between turning the truck off, going to "on" setting, seeing if it kicks over.... trying again....etc. My mechanic who I trust, thinks that we should replace the Transfer Case Acuator Motor. Which is a $900 part plus labor.

Anyone have any experience with Transfer Case motors, OR damaging the transfer case itself ( a possibility) during a drop in like I described above? Thanks in Advance!

 

heres a good thread on the actuator

https://www.tacomaworld.com/threads/how-to-trouble-shoot-4x4-actuator.263525/

lots of problems with corrosion etc for the actuator, might be a coincidence who knows

 

Yea, I've read alot of the actuator threads. Most of them are about the front diff actuator. less about the transfer case....

 

ouhhh i missed that, my bad lol

 

I have the same problem it is stuck in 4wd after commuting in the snow, going to be testing and looking at the actuator and testing the transfer pressure switch system.

did you ever figure out what the problem was?

 

Interesting.
There are a few components that feed back to the 4wd ecu in order to determine whether it is in a good or bad state. Blinking, obviously, means bad state.

The transfer shift actuator assembly itself has a few feedback lines (TL1-3), and the transfer case itself has two additional sensors, 4WD and L4. If the inputs don't all reconcile with each other, then it will blink.

I don't think that a big "clunk" would impact the transfer shift actuator assembly. If something broke off, it could potentially cause damage to the sensors on the 4WD or L4 lines. Obviously it isn't the L4 line causing you problems, since the issue is between H2 and H4.

The first thing I would do, is check the status of TL1-3 and 4WD lines to the 4wd ECU.
In 4WD, they should read as follows;
4WD: 0 resistance to ground.
TL1: floating
TL2: 0 resistance to ground
TL3: floating.

In 2WD, they should read as;
4WD: floating
TL1: 0 resistance to ground
TL2: floating
TL3: floating

The 2-4 transition is like this;
1) TL2 changes from floating to 0 resistance to ground (TL1 and TL2 simultaneously 0 resistance to ground during transition),
2) 4WD transitions from floating to 0R to ground.
3) TL1 changes from 0R to ground to floating. This tells the 4WD ECU to stop the motor.

The 4-2 transition is like this;
1) TL1 changes from floating to 0R to ground
2) 4WD transitions from 0R to ground to floating
3) TL2 changes from 0R to ground to floating. This tells the 4WD ECU to stop the motor.

If at any point, the state of the sensors becomes "impossible", it will error out. For example, TL1 and TL2 can never simultaneously be floating, EXCEPT when in L4 (TL3 0R-GND). There is NEVER a state when TL1 and TL3 can simultaneously be 0V-GND, etc.

It also will use the L4 and 4WD switch states to determine if it is in an impossible state. For instance, L4-GND while TL3 is floating. L4-GND while 4WD is floating.

If it ever finds itself in an impossible state, it will shut down, could get stuck at whatever position it happens to be in.

If it ever finds itself remaining too long in a transition state, it will also shut down. Given how you describe partial function during the ignition on but engine off state (i.e., just after turning the ignition on), I suspect a timeout situation. When you switch the ignition on, the 4WD ECU will read the switch position, and attempt to adjust the transfer case and ADD into that state. If you leave it, it times out and gets stuck there.

You can try overriding the motor by applying power directly to TM1 and TM2. Reverse polarity to reverse the direction.

My concern is that the big "clunk" broke something in the transfer case, which is preventing the actuator from pushing the shift rod fully into the 4WD position. I suspect that the state of the lines is as follows;
TL1: 0R-GND
TL2: 0R-GND
TL3: floating
4WD: could be either 0R-GND or floating, depending on where exactly it stopped.

I don't think that there is any other possible connection between the clunk and the blinking light, except for a coincidence.

In order to diagnose such a mechanical failure (which is essential before spending huge money to replace the transfer shift actuator that might not be broken), remove transfer shift actuator, and attempt to operate it manually through all three positions (H2->H4->L4). You can do this by grabbing the shift rod with something like a vice grips (through a chunk of rubber so you don't damage the shaft) and move the rod. While doing this, you should also validate the state of the 4WD and L4 sensors.

 

Wow, Thanks for that awesome information! I'm gonna have to read your post a couple more times to make sense of it. I do plan to remove the actuator motor to inspect it before I have to simply get it repaired. When you are talking about removing the actuator and testing it via moving the rod, you must have to remove the transfer case as well? I understand that you can remove the actuator motor itself only by removing that tiny sprocket and leaving the rod in the transfer case. How would I access the shift rod otherwise?

 

The whole thing comes off and apart.

 

Ok UPDATE:

last night after finding a used actuator motor online- we swapped the motor out and I now have full mechanical shifting between 4lo 4x4 and 2hi. I have solid dash lights for 4x4 and 4lo. However when I shift back to 2 wheel drive, the dash indicator is still flashing.
The rig is in 2wd, the dash light just is flashing, won't disappear. Any thoughts guys?!?

 

Try finding one at a junk yard. Cheaper to diagnose it that way.

 

The front diff may not be unlocking now. You'll need to jack it up and see if the axles are connected in 2WD mode.

 

Time for a 4runner/ FJ t case

 

I was seriously considering that. However I decided that that was a move in a direction I'm not ready for yet.

 

Hello everyone
Just had my truck in and found a couple of things out that may be related to this if you are having the same problems.
2009 Double Cab, short box TRD offroad
The other day I was running errands and when I started my truck up, it engaged the 4H wheel drive even though the switch was in H2. Couldn't get it to switch to either 2W or 4Lo, so took it to the dealer. After a couple of days at the dealer, they found that it was the detent switch in the transfer case actuator that failed. Might be something to check if you truck will not come out of 4H. ~$200 part, but worth it to know it was not something worse.