4WD actuator problems - feedback?

I'm pretty sure they sell it alone and you dont need to replace the TC but the TC needs to be disassembled. Old school TC motors were easily to replace, usually unplug, a couple bolts and done. It would make sense that Toyota would do a full replacement because its probably easier

 

Hopefully it's that easy. Time will tell...

 

it could be the front actuator on the tcase that was one of the parts that failed for my buddy.

I dont see why the Tcase would be ruined in this case.

And the front prop spins in which way? When 4x4 is engaged? or disengaged.
the front prop can be turned freely when in 2wd.

 

Unfortunately the fact that the front ADD is locked and the transfer case isn't doesn't necessarily mean anything depending on what has happened at the shop. It might or it might not, depends. For example, if the 4wd ECU detects an issue with either the front ADD or the transfer case actuator on ignition start up, it instantly disables all mode changes and blinks, before it allows any motion. It doesn't matter what position the actuators or the cockpit switch is in. Only if the ECU thinks the system is OK on startup, does it then consider moving the actuators to match the cockpit switch.

On startup, the ECU checks the resistance of the ADD motor and the Transfer Case motor. It also checks for valid readings of the position feedback on the ADD Actuator and the Transfer Case Actuator (positions match ACCEPTABLE positions programmed in the ECU, not necessarily the current cockpit commanded position).

Note, I am not sure what the issue is without more data, but just giving some examples here to show how the system responds.

So, lets say the ADD actuator was in the locked position when they installed it, and the issue is with the Transfer Case Actuator somehow broken and the ECU detects it. When the truck is powered up, it detects the issue and it locks out all 4wd mode changes. So ADD is still locked, transfer case is unlocked, and truck is blinking....

Now lets say again ADD installed in locked position, but the issue is with ADD wiring. On startup the ECU detects the issue with the wiring and it locks out all 4wd mode changes. So ADD is locked, transfer case is unlocked, and truck is blinking....

So in either case, you can have same general symptoms with different causes.

With techstream or an ohmmeter we can figure it out, but it will take some effort.

But it seems unlikely that there is any actual issue with the transfer case actuator to me, as the symptoms initiated when the front diff was honked up. Chances are (99% I think) that the issue lies with the front actuator (or its installation), or the wiring to the front actuator.

Sorry this wasnt more help.

 

I think you should just have the shop bring it to Toyota and have them fix it properly

 

Thanks, @BigWhiteTRD. Good info there. Would be great for either the shop or Toyota to really dig into that and figure things out, but I'm really not sure either will spend the time before throwing more new parts at the problem.

@Joe23, Toyota already looked at it and said the issue was the ADD. The ADD was replaced this morning and nothing changed. It's back in Toyota's hands, and I'm hoping they will look at it again tomorrow. Haven't seen the truck since Monday...

 

Just went through this exact same thing two days ago after getting my re-gear. I had the flashing green 4x4 symbol on my dash along with the 2wd-4wd mode change failure. Shop told me it was the ADD when they tested it, brought it to Toyota since still under warranty. Initially, Toyota told me it could be due to 3 potential issues, 1) wiring harness, 2) ECU and 3)ADD. I initially told them I thought it was the ADD but they ran through the protocol but eventually their test did ID the ADD as the issue.

 

Thanks for posting repair order. Helps to understand likely failure modes. From the write up, the motor circuit was open, implying add motor burned out. (This motor resistance is an item ECU checks on engine ignition on, before commanding any changes)

 

Agreed, although at the same time, as long as they fix it, who cares... The big issue I think, is when it seems like just a little more research and testing would lead to the solution much quicker...

As always, good luck.

 

Another day and no progress. The fellas at Toyota can't figure out what's going on and there's now talk about replacing the transfer case. The shop has finally taken BigWhiteTRDs info a little more seriously and will be passing it on to Toyota.

 

Stopped by the dealership this morning. They had the truck on the hoist and had just drained transfer case fluid. It was very metallic, almost silver coloured. There was talk of replacing the TC with either a used or new unit. Don't think I'll be settling for a used TC - I want this done correctly. No idea how long it'll take to get parts in.

The dealership's tech did confirm that the truck showed an open circuit in the ADD initially, which is why that was replaced. Now the ADD is fine, but the truck is still stuck in 4WD and won't shift into 2HI at the transfer case. Sounds like the shop actually drove the truck from their place to the dealer (a good 20 mins on pavement) in 4WD - I'm not thrilled about that thought.

A few days ago the shop had mentioned a "what if" - they had put in a wrong gear ratio in the front diff, or left the old one. The installer asked me to again recall what I had done with the truck and what I encountered, and seemed satisfied with the result in that it confirmed that he didn't make a mistake and DID put 4.88's in. With the TC fluid being as metallic as it was, I'm wondering whether that might actually be what happened...

 

If the fluid is that metallic, certainly sounds like that could be what happened. Gears got mashed

 

Thanks for letting us know how it goes.

So is this the latest working theory, (just trying to match up to the symptoms, etc)?
Shop installed new gears in rear, they didnt put new gears in front but did leave some copper tube in the front.
The copper tube jammed the front ADD, which burned out the ADD motor when the truck was switched to 4hi with jammed actuator, which then locked out all further mode changes due to the open motor circuit.
New ADD installed.
Truck goes into 4Hi and then further mode changes are locked out.
We are guessing that the truck couldn't change out of 4Hi, because the front and rear axles were always binding against each other due to the mismatched gearing.
The transfer case actuator was damaged.
The truck was driven in 4hi with mismatched gears, causing excessive wear on the transfer case.

Is that the latest theory?

 

Got this from the shop. I believe he means that metal was found in TC oil, not diff.

 

This is one of the many skepticisms I have with electronic controls all over the place. Can't beat a good old gear selection lever. Best of luck with everything!

@BigWhiteTRD I envy your knowledge and perspective on this. Always a good read to have info like this!

 

Spoke with the shop. He's got a used Transfer Case (off a 2017 Tacoma with 20k km on it) coming in tomorrow. A used part is not my first choice, but given the time crunch (I absolutely NEED my truck by Friday) and associated costs, I think it's the only realistic option. And he will warranty the TC himself should anything arise. Probably not the worst outcome.

About 4 hours to RE/RE it. Hoping for good news tomorrow eve.

 

Man, you messing up my beautiful theory with reality.

So I assume they mean to say TC actuator is jammed, not diff. (Just like TC oil not diff oil).

I have no good ideas now, that is for sure.

 

Update time?

 

Yessir.

Spoke w/ the shop. The replacement TC arrived late in the day so they couldn't install it - that's planned for first thing tomorrow morning.

They did pull off my TC and found a heavily damaged piece of aluminum. They/we are not sure of the proper name for this piece, but it's the chunk of metal that goes into the 4WD fork in the TC (engages it, if you will). This piece was not only damaged, but also turned roughly 90-degrees from its expected orientation.

Current working theory is that the front actuator (in the ADD) jammed due to the left-over pice of copper, and as I turned the knob to put the truck back into 2WD, the TC received erroneous input from the ADD and tried to shift the actuator at the TC, despite the front actuator still being engaged. This - either through torque transfer via the front prop shaft or via a localized (ie. in TC) mismatch between some components - caused the physical damage, and essentially locked out the entire system.

Replacement TC going in tomorrow morning.