Front Diff/Transfer Case Actuator Diagnosing

I wanted to do a write up so there is one place for someone to have a methodical list of how to walk themselves through figuring out most likely what is going on with their 4wd system before taking it to the dealership or straight to removing actuators. So here we go (if you want to read my rambling back story first, skip to the bottom now):

Chain of Events: assuming all is hunky dory the way this system should work is: knob is turned --> signal is sent to ECU --> signal is sent to T-Case Actuator (front drive shaft is given life) --> signal is sent to the Front Diff Actuator (CV's are locked in and you are now in 4HI). ***The reason this is important to understand is because if something doesn't engage in this chain it affects the whole thing. The system kicks back but will keep trying until the knob is turned.

Signs/Symptoms: turn 4wd switch and either nothing happens, engagement is delayed, or will engage but not disengage. Always followed up with 4HI light flashing, and in some cases the 4LO light will flash and the VSC will stay solid. If you run a scan and no codes appear don't be surprised. If there are more lights flashing/solid then just these then it's most likely something else.

Causes: As far as I can figure out, if there are more that i've missed please let me know!

1. 4wd Switch has failed (turn knob and nothing happens; can be intermittent)
2. 4wd ECU has failed (rare; will present like a failed switch)
3. 4wd system wiring issue along the undercarriage
4. Transfer case actuator motor has seized
5. Front Diff actuator motor has seized
6. Something not involving the 4wd system is messing with the 4wd system.

Diagnosing/Testing: my 2 cents: Rule out the easy stuff first (switch, ECU, non 4wd system issues)

1. Step #1: Visual Inspection (ruling out non 4wd system issues) -> please please please for the love of Buddha check your tire pressure and ABS/wheel speed sensor wiring. I know it sounds trivial but these can cause some of the same problems and you will save you time and money.
2. Step #2: Ruling out Switch/ECU -> if you're turning the 4wd shift knob and nothing happens (most of the time) no sounds, no lights, nothing. It is most likely the Switch or ECU, if you go through everything piece of this chain and ruled everything else out come back to these two. Testing the switch with a multimeter is as reliable of a test as one can do in shop or at home to figure out which it is. Now assuming there are lights flashing or a sounds coming out of the bottom of your truck:
   
3. Step #3: The "Whir" Test -> turn your truck to Power and then turn the 4wd knob to 4HI. Crawl under your truck so that you're laying right underneath the T-Case. Listen for a whirring that turns off vs a humming/beeping. If you hear any electrical noise you can assume, for now, that the Switch and the ECU are working properly. If you hear a humming and beeping it most likely means that the T-Case actuator is working and the issue lies some where in-between the T-Case and Front Diff with the Front Diff actuator being the likely culprit. If you hear only beeping then the T-Case actuator motor is most likely seized.
4. Step #4: Multimeter Testing -> only do this if you are comfortable and really want to confirm what is going on. The sound test will mostly give you the answers you are looking for. It takes time and use of wiring diagrams which some may not have access to. It also requires unplugging connectors which will throw codes and make your dash board light up like Christmas, so it helps if you have someone who can clear them for you. I tested in order of switch, T-case actuator, and then front diff actuator and is how I verified all of my suspicions. My truck has no electrical issues however the wires are exposed and easily damaged can be the cause.
5. Transfer Case Actuator --> Found to the rear of the T-case surrounded by a guard plate. Now I trust you have done your own due diligence to verify your T-Case and Front diff at mechanically sound and operational... (I take no responsibility if they are not....). Once again if you hear the whirring you're good, the actuator at the T-Case is working and sending the signal forward. The difference between the hum and the whir is the front diff actuator doing its job by moving the fork. If there is no noise as the system cycles the actuator motor is seized (most likely). Yes that is correct, that is the issue with these actuators.... the weak link is that moisture gets in and corrodes the internals so much that the motor seizes.
6. Front Diff Actuator --> found to the front of the front diff right at the back of the factory skid plate. Setup almost the same to the T-case actuator just smaller. Apparently the more common one to fail in the Gen 2 Tundras (so I'm told). In my case this is where the beeping is coming from and where the motor is only functioning sometimes.
7. Vacuum hoses --> wondering how moisture gets in? Well Toyota decided that these actuators needed "breather" hoses which some refer to as vacuum hoses (harking back to prior Gen trucks). They are NOT vacuum systems (fully electric) and these hoses for breathing purposes apparently. HOWEVER they like to degrade, get cut, and/or get torn, when this happens they let water into the actuators internals. Keep up on these and you will avoid A LOT of headaches.

So there you have it, if your T-Case actuator makes noise it is working and the issue lies at the Front Diff actuator. If there is no noise but the system shows itself faulting then the issue lies at the T-Case actuator. If there is no output for your input then put your head between your legs and pray that it's the switch or that you've got warranty left. Once you get the system to engage, and disengage without issues MAKE SURE once a month you put it in 4HI and drive enough to let the parts warm up. This will also save you the headache of wanting 4wd and not having it.

Thanks for reading and hope this saves someone some time on diagnosing a silly problem that our trucks have inherently.

My Long Rambling Story: It all started mid January on our way to Quebec for a ski trip at my wife's families cabin which has a steep hill to the driveway and I knew it hadn't plowed yet. So I go to put it in 4HI to hammer up the hill and the system hesitated then engaged. Parked, noticed that the 4HI light was flashing, shifted back to 2wd and the flashing stopped so didn't think anything of it. When we went to leave a few days later it clunked out of 4HI and I knew something wasn't right. Thus started the 6ish months and countless hours scanning through Forums, Youtube, Google PLUS talking to my buddies at my Toyota dealership PLUS fiddling around myself to figure out why the crap my 4wd system acts like a pissed off teenager. I have finally been able to figure out what is going wrong with the system. On the plus side I haven't spent $1 on diagnosing fees or lost any friends.... Thank the lord for beer and Timmy's (for those of you down south pick your favourite coffee shop and swap the name). My issue was that it was so intermittent, I had a few times where I really needed 4wd for creek crossings and such that it would go in, but other times where it would be all of the symptoms or none... I figure the motor is failing because it's to intermittent to be a seizing issue. However I have the parts ordered and it's going to be replaced under warranty. I will update with some pictures of the inners of that actuator once I get my hands on it and tear it apart.

 

What’s the modules name or do you happen to have a part number to reference

 

Need some help, ladies, and gentlemen....desperately.

So...here's my situation.

2011 Tundra TRD 4x4 SR5 CrewCab 5.7 FFV, Black (The best 60-0 time colour).

Shifting into and out of 4hi works VERY sporadically, and fails 99% of the time.

Occasionally, if I can get the truck to shift into 4hi, and back out, I can switch back and forth freely for a short time - it works like it is supposed to (I can even get to 4lo). This is over by the next time I fire up the beast.

But, as you can see...this is a problem.'

Most of the time, I am able to drive around with no "bad lights" (no vsc, no flashing 4hi, etc.) in 2wd. That is, until I try to shift into 4hi. The majority of the time, I hear no noises, and just get the flashing 4hi. Or, I may get the start of what sounds like a front diff action, but then it does not complete, and I get flashing 4hi, and I end up somewhere in no man's land.

When the shift failure happens, the result is often 2wd that feels like 3wd. Or at least that the front left wheel is locked to the back two...or to the front right? Either way, I get wheel hop from the front left, frequently, when this happens (but not the front right). It does not feel like any of the front wheels are powered, though - just that the front left is locked to one or more of the other tires.

Up until about a week or two ago, 2wd worked fine. The other day, I was backing out, had the wheel cut hard to right while reversing, and got a nice little "pop" from the front left. When this happens, it seems like it is the front left "locking" into rotation with another tire. Normally, shifting into 4hi and back to 2wd (after many, many tries) fixes this.

However, this time also includes a CLUNK CLUNK CLUNK (etc.) when the wheel is cut hard, and when driving down the highway (with no 4wd lights flashing, no vsc flashing) I am hearing a very noticeable grinding? sound. It sounds like metal cylinder on a metal cylinder, rather than a chunky grind - its more like metal flush with other metal. I am also now getting a "clunk" from the front left when I go over bumpy areas - which sounds similar to the CLUNK mentioned above that I get with the wheel cut hard.

Currently, I am unable to shift into? out of? 4wd. It seems that the front wheels are not being driven, so in that sense, it feels like 2wd. However, there is a significant uptick in noise from the front left (clunk and grind), and I have the dreaded 4hi flashing, again. However, all of the previous tricks that I used to get the shift to occur (putting it in neutral, turning the key to ON but not starting the truck, etc.) are no longer working.

HISTORY:

I purchased the vehicle, used, about seven months ago. Thus, the issues detailed here existed from the start of my ownership. The 4hi light was flashing and the VSC light was on, and it would not shift into 4hi, and I had no traction control whatsoever.

My assumption, if that moisture got in via the cracked front diff breather tube (which I am replacing once the part gets in), and caused the motor/work drive in the front diff actuator to malfunction. The worm drive was rusted and would not move. My second assumption is that because of this, the vehicle was not used in 4wd (as the manual recommends), and the front diff collar became stuck/non-operational. Additionally, the vehicle seemed to be in that "3wd" mode, and for who knows how long, so I have no idea what damage has been done because of this.

OBSERVATIONS:

With the vehicle running, when I have a failed shift (and have the 4hi flashing), nothing happens when I continue to change the 4wd knob. I don't hear the clicking from behind the radio, and don't hear anything from the front diff (other than the beeping, sometimes, if I am outside of the vehicle). Sometimes, if I switch to 2wd and drive a bit, I'll get the satisfying "clunk" of the front diff uncoupling and things are back to normal 2wd operation. Sometimes that doesn't work, though, and have to try the next method.

With the vehicle off, I set the 4wd dial to either 2wd or 4hi, and turn the ignition to ON. Whether it's 2wd or 4hi, it doesn't matter, I hear a click-click from behind the radio, and then hear mechanical noise from the front diff (what sounds like a whirr-clunk) - it sounds very much like the front diff trying to move the fork/collar. This noise, however, can be either short, long with a clunk into position (either 2wd or 4hi), or occasionally, no noise at all (though this is very rare for this method).

Typically, doing this a handful of times will get the shift to complete successfully. Again, this is with the truck not running, just by turning the ignition on. If I turn the switch to a different position than it was in when I turned off the vehicle, I get the VSC light - but it's still possible for the shift to complete if I drive around (this has happened and the vsc light went off when I turned the truck off).

What I find interesting, is that most of the time, I can get at least the start of a front diff shift just by turning the ignition on, but if I start the truck and turn the dial, nothing happens. Turn it off, turn the ignition on, and again I get some mechanical noise and the click-click from behind the radio.

Now, though, this doesn't seem to be working. I started to get, for the first time, NO noise at all after the click-click. Not long after, though, I once again began to get mechanical noise after said click-click. But that noise has not ended up in a CLUNK, indicating a successful shift, and so the 4hi light has not stopped flashing in this round.

Right now, turning the vehicle's ignition on, but not starting it, one of a couple of things happens:

A. I hear a short clunk from the front diff, and then a long beep, followed by many short beeps.
B. The VSC light pops on, and there's no noise from the front diff at all.
C. It seems though I am not positive, that I can hear a very light zzzzz noise from the transfer case actuator sometimes, but not others. Sometimes the front diff makes a zzzz - and I can feel slight vibration from the actuator motor, and sometimes it doesn't.

STEPS SO FAR:

I have replaced the front diff actuator assembly (electronics and fork pieces), drained and replaced the front diff oil twice (once with a cheap oil and the second time with Red Line). I did it twice because I wanted to replace the actuator before I went out of town, and the auto parts store didn't' have the oil that I wanted to get at that time.

I have replaced the transfer case oil with Red Line, as well, and I inspected the 4hi (I believe) actuator. Base don some of the horror stories I've read about with gears falling out, I just opened up the actuator and visually inspected the contacts, gears, etc. inside. It was pristine (at least compared to the front diff). There was no rust, plenty of dielectric grease, etc. The breather was no longer attached and had some cracks near the nipple end, but I taped it up for the time being, stuck it back on there, and moved on. Despite the breather being unattached, it did not appear as though moisture had been an issue in that part.

When I had the front diff actuator off, and could see the collar, I tried manually articulating it, but it would not budge. I'm not sure how much force is needed to move it, so I don't know if it was "stuck" or if the issue was solely bc the motor on the previous unit had ceased functioning.

My understanding is that the 4hi flashing indicates that a "shift cycle" (2wd -> 4hi or 4hi -> 2wd) did not register as complete. It seems as that when my truck fails to complete a cycle, it's left somewhere in-between 2wd and 4wd - 2wd, but the front two wheels are not totally independent. Previously, when the cycle DID complete, 2wd was fine...now it seems as though the cycle is either not completing even when it registers as so, or something else (possibly damage from driving it in "3wd" could be causing the metal grinding / clunking noises).

Also, I believe that the VSC light comes on when the vehicle thinks that it cannot communicate with the front diff actuator (and possible when it's confused - like when I start a shift, it doesn't complete, I turn the truck off, and then start it with the dial in another position).

I do have Techstream, but the only info I could get from that, regarding this issue, was before I replaced the front diff actuator, and I had the constant VSC light along with flashing 4hi, was that the system read the VSC system as being in "VSC Expert Mode" - but I was told this was just because the system couldn't communicate with the front diff, so it disables the VSC system when that happens.

I am seeing a bit of oil around some of the front diff seals...I just topped off the front diff oil today -it was down about 1/3 of a quart (but some of this could have been attributed to the oil moving around throughout the diff after I filled it last time).

My next step is to take the front diff actuator (just the electronics) off again, make sure all of the gears, etc are aligned properly. If that doesn't fix anything, I guess I will be taking the whole assembly, fork and all, off, and making sure that is all aligned properly, as well.

Any help at all would be appreciated! Please see the above steps and information, as I have already employed most of the suggestions found around the forums.

Thanks!

****UPDATE****

Everything is working fine, now, it seems. (It has been for a while, I just forgot to come back and update this).

The issue was...apparently, when I put the new front diff actuator back onto the [part with the fork] I misaligned the gears. :/

This caused quite the confusion for the old gal (the truck, I mean). When I would try switching into 4hi, the actuator motor would spin up and try to move the contacts along...which it would do...but I think it was (bc of the misalignment) *starting* in the position of either 4hi or 4lo (with the in-cab selector switch in 2wd)...so when it tried moving from (what it thought was 2wd -> 4hi, it was actually trying to make that movement starting further along the connections path (either in 4hi or 4lo)... and then, I think, it would run out of real estate and "snap" back into the old position (or another wrong one) - as inside its basically a "spring" of sorts, along with some gears that move an electrical connection point along a path...which then tells the fork what to do.

I think this *might* have also caused the transfer case to get out of whack, as well, thinking it had moved the front diff.

So in the end, the solution to my original problem (blinking 4hi, no 4wd at all, etc) was replacing the front diff actuator. If I had lined up the gears right the first time, I think the problem would have been alleviated.

Lesson for the kids...always line up your gears correctly.

 

I second what he said. Part numbers would be helpful. I am getting misinformed as to correct part numbers and the only part I can find for the transfer case 4x4 shifter i sonly available with the shaft installed on the actuator. I dont need the shaft and buying the just the bolt on actuator assembly would save me hundreds. Thanks

 

This video helped me understand the system better.

https://m.youtube.com/watch?v=47m7QAPrpsI

 

I have a weird issue with my 2014 CM....

My 4H and 4L flash and my ABS/Traction control lights stay solid. When the 4H and 4L are flashing, the truck will not engage into 4WD.

When I shut off the truck completely and restart it, the 4H and 4L lights stop flashing and when I put the truck into drive, the ABS and traction control light shuts off. Then, the truck engages in 4WD (4H & 4L)

During all of this, I am not getting a CEL. When I find the time, I'm going to go back through the OP's notes and check some things out.

 

Have been diagnosing a failure to shift into 4wd. Followed the above. Heard the TC actuator motor whir, stop, then reverse. No sound whatsoever from ADD. took to shop this morning and they said there is error code P17ac- Transfer case limit switch. Will pick up tomorrow and get estimate of what is needed and cost.

But I am assuming the TC actuator is not fully engaging or the limit switch is bad. Also assuming that the ADD does not try to engage until the transfer case has completed? And this is why I hear no sound fro the front?

 

Just realized my may be different than above by a little as it is a 2014.
Here is the thread I have for this issue.
https://www.tundras.com/threads/4hi-error.69820/page-2

 

Howdy folks, I've been trying to fix a 4x4 issue on my 2011 Tundra. When I try to engage 4Hi, the light blinks slowly as it normally would but then after a few seconds it begins blinking faster and fails to engage 4x4. I hear a relay clicking behind the glovebox when it first attempts to engage and then when it fails and starts blinking faster. I can confirm that the transfer case actuator is not frozen up because I opened it up today and checked the motor for freedom of movement. With the engine off and the key in the 'on' position, I can hear the transfer case actuator move when I select 4Hi and then hear it move again when the light starts blinking faster as it fails to engage.

I know that the computer runs a series of quick checks between the transfer case and front diff actuators. My question is the order in which everything happens. What I think I am experiencing is that the transfer case is engaging, then asking the front diff to engage. When the front diff fails to engage, the transfer case reverts back to 2Hi mode. Is that correct? Or is the transfer case failing to engage before it's commanding the front diff to engage?

The 4wd has been intermittent for the past several months and being stuck in 2wd nearly bit me in the butt the other day so it's time I get this sorted out. No warning lights are coming on during this process. However, maybe 2/10 times that the 4wd does engage, the skid light comes on with 4Hi (the square light with 2 squiggly lines).

Anyone have any thoughts? I guess next I am going to attempt to see if maybe the front actuator is locked up



Edit: How the heck do you remove the front diff actuator? The screw on the top seems impossible to get to unless my screwdriver was a wet spaghetti noodle.

 

No CEL? Seems like you’d get one. Maybe there is a hidden CEL. Do you have a code reader?

 

No CEL. I don't have a reader handy to see if there are any pending codes. Ultragage is in the Tacoma and not easy to remove

 

See my above post for lengthy details... but I did not have a check engine light, either. Bc of the front diff actuator being out of commission, I also did not have skid control, etc. (and what seemed like no ABS), as when the system sees that it can't communicate with the front diff actuator, it goes into a limp mode (which almost caused me to get into two accidents in one morning on some patches of ice...and sent me into limp mode, as well).

 

Switch -> transfer case -> front diff actuator, is the order of operations.

It sounds like you are on the right track. For me, I bought the truck used, and it came with the dreaded "moisture getting in via broken breather tube and rusting the front diff actuator worm drive to the point where it would no longer function" problem...

[Make sure to note the whirr/beep/etc. diagnostics, as outline in the first post, to confirm where the issue is.]

An additional problem these trucks can have... is the front diff fork getting stuck, which is why it's recommended to engage the 4wd once a month and get that lovely oil all squishing around.

I know some people have had issues finding the correct replacement, as, if I recall, there's some mislabeling online as to what is needed and what is being sold, exactly. Here is what I bought, for a 2011 CM: New For Toyota Sequoia Tundra 4WD Front Differential Shift Actuator OEM SAT011 (https://www.ebay.com/itm/New-For-Toyota-Sequoia-Tundra-4WD-Front-Differential-Shift-Actuator-OEM-SAT011/362726463315?ssPageName=STRK%3AMEBIDX%3AIT).

As far as getting to the screw... I purchased a flexible right angle drive extension, as well as a straight extension. Note, I have a decent size lift on there, so I may have had some more room to work with, but those are the two things that I utilized. I would see if a right angle (flexible shaft) adaptation would help. Take heed though, you could strip those screws out...I was really surprised at the ones they used, and some barely remained serviceable after taking them out. If I recall, I had to use a metric ton of penetrant spray to unlock them.

I actually ended up taking off the plastic housing of the actuator and the body that contains the fork. If you do this, be prepared to catch all that oil and have some replacement oil, as well as a pump to get it up into the re-fill hole (and washers, the red sealant stuff [I forget the name], etc. if you want). If you absolutely can't get the black plastic housing open (which contains the worm drive and gears), then you may consider taking the entire piece off and draining/refilling the front diff oil.

It sounds like your best bet may be getting that housing open, and checking for moisture damage, aka rust. Check the breather tube and see if it's broken, too. Be careful though, if you take the housing apart, not to dislodge the gears and have them fall out. Also, obvious, but take a pic once you get it out in-case you need to realign them (noting where the contact points are AND what position your selector is in. This was my second issue...the actuator contacts were lined up in the wrong position (e.g. actuator was in 4hi, but selector in cab was in 2wd).

You may be able to just clean off the worm drive, contacts, re-grease it, and slap it back on (I was not).

The transfer case also has a very similar looking actuator which I adventurously took off to check things out when I had screwed up the gears.

Hope that helps. I'm sure it's way too much info that you already know, but maybe it can also help someone else out. I went through this whole process and it was quite a learning experience (especially when you misalign the gears...).

 

Did the shop confirm that the signal is not getting to the front diff actuator?

I'm not sure what your shop will do, but if you take it to Toyo, my understanding is that they will tell you they have to replace the entire transfer case actuator, bc they won't replace just the actuator cap/switch.

Mine is an '11, but it may be similar enough to yours... you can open up the actuator, and see the contacts, switch, etc in there. At that point, you can inspect for anomalies, clean, re-grease. If the switch is bad, it's a lot cheaper to just replace that black cap than the entire transfer case actuator. Most people online, if I recall, sell the entire actuator assembly... so unless you can find just the cap, you may want to investigate buying the actuator assembly (like off of eBay) and then popping it open, and just replacing your old cap with the new one. That's the trick... The dealer will tell you that they have to replace the entire actuator...which involves a LOT of man-hours taking the transfer case apart, bc the new actuator comes with the rods, etc.. Replacing the cap is much, much faster and cheaper, and probably the fix you need if it's a switch problem.

 

Thank you for your detailed response. I would like to just free up, lubricate, and reinstall the actuator for starters. To continue from your points...

I can hear the transfer case actuator whirring. After it makes this sound and I turn the main driveshaft by hand, the front driveshaft also turns. I hear no beeping or whirring from the front diff, and then after about 8 seconds or so the transfer case actuator whirrs again and disconnects the two driveshafts.

Ideally, I want to only remove the plastic cover exposing the gear in the ADD actuator but I don’t think I have the tools to get to that screw. Instead, I think I’ll have to do it the messy way and unbolt the whole assembly from the front diff while also draining the gear oil. I happen to have some 75W90 gear oil left over from my Tacoma to refill it with and I bet I can round up some red RTV to seal the actuator housing back up. If I can get it up onto the bench, I think it’ll be easier to take apart and hopefully be less likely to strip out those screws that people seem to have trouble with.

I checked the vent line today, and it was intact on the ADD actuator.

Here’s a photo of my 4Hi actuator that I was thinking was going to be the culprit....it looked brand new and has 213k miles with a ton of off road use. I was shocked.

 

I am having to replace my steering rack so this is a perfect time to investigate the front diff actuator since I have to remove the differential.

I got the front actuator housing apart and there is no evidence of corrosion inside. I disassembled it further to expose the shaft and electric motor. Might I suggest anyone else to NOT do that because I had to play a very expensive game of Operation to put it back together. Everything checked clean of corrosion in there too. Is there a way I can test the electric motor in the actuator on the bench? I see 6 connections in the plug so I’m wondering if I can hook 12V power and ground to two of the blades and see if the motor spins.




Edit:

I also put a tear the driver side differential seal when removing the CV from the diff/removing the diff from the truck

 

Update of my troubleshooting:

I found the wiring diagram for the 4x4 system and was able to check the front ADD motor to be sure it spins. It appears to be working fine, but it doesn’t seem to spin up when it’s all installed on the truck. Next, I guess I’ll have to test the plug to see if it’s supplying power when 4hi is selected with the switch.

https://youtube.com/shorts/vDANHHv-R2Q?feature=share

 

Did anyone get codes like U0114.
While having this issue ?

 

Is there a limit switch on the transfer case I can test?

 

@Yotaholic any updates? I am having the same issue.

 

No, I haven’t had time to dive back into it

 

2002 tundra 4.7L 4wd

My 4wd dash light is blinking. PLEASE READ ON. I already replaced the transfer case actuator and front differential actuator. My 4wd works when I press 4hi button on dash and comes out when i press again. But 4wd light on button and dash blink when in 4wd. No blink when out. 4lo button does not stay in when pressed and 4lo does not engage or blink at all.
When replacing the transfer case actuator I moved the gear rod into 2wd, 4hi, and 4lo successfully. I know the transfer case and front differential are working fine.

Anyone know why my light is blinking and no 4lo???? Please

AL

 

Hi. Sorry I can’t help you with your problem, but in this thread we are discussing the 2007-2013 Tundra and the 4x4 systems are different than yours. Try searching elsewhere on the forum, I hope you find your answer!

 

I think there is more to this issue than following the basic guidelines in the initial post. I have been having the same similar issues as Yotaholic and doubt this is a simple timing issue. Just for the heck of it, I went to the local yota dealer and they just said the same thing I told them when I brought it to them. " Your 4wd case is not fully engaging so you need a new case and updated ECU. I demonstrated the same scenario when I dropped it off this morning. The gears appear to work fine when manually controlled with the actuators removed. Is there some other adjustment in the 4hi actuator or bad ecu to cause the reset after about 10 secs back to 2wd. The actuator will engage the front shaft during those 10 secs. Thanks

 

I find that to make sense. It will engage electronically and did for an entire day after actuator replacement. However, the dash and button lights were blinking the whole time. The next morning it would not engage. At this point I don’t mind having 4wd full time and using secondary roads in order to enjoy the beach fishing.
Then i can look for a transfers case in the bone yard if diagnosed as such. I am still hoping to time it up this morning and get lucky just one time.
AL

 

If I manually lock in 4wd on a lift by moving the transfer case shifting rod to 4hi and spin the front wheels to lock in the front axle, will it stay in 4hi as long as I keep the actuator disconnected?

AL

 

Update, maybe this will help some as well. After resetting the actuator many times with the same results, i tried to initialize while in N vs Park when engaging 2wd to 4wd. Everytime this was done, i had the partial engagement. As soon as i reset, put in N, then switch 2wd to 4wd, the intial setting/activation found its happy home setting. Even if timing was set perfect and initialized from park, the setting would never correct itself. Going to run by Toyota and ask them why they insisted i need a new ecu and TC. Would love to the ask the tech what he actually checked. Too funny, but sad for those that cant work on their vehicle.

 

UPDATE ON NOT YOUR USUAL 4WD PROBLEM.
I wish I had better news. This morning I removed the transfer case actuator and front differential actuator. These are brand new. Using every bit of knowledge retained from these postings I reinstalled both of them. On a buddy’s lift we checked them as we installed them for correct positioning. Up and down on the lift. With the round gear beneath the black cover rotated to 3 o’clock and plugged back in no blinking dash light. Install the gear and seal up the triangle. Test just off the ground in neutral engine switch on push in 4hi button and light on dash blinks as transfer case actuator rod moves to 4wd position for sure. Front axle does not lock in and no differential actuator sound. After many attempts the new differential actuator is removed and checked looks good. Axle clutch is moved right and left to lock and unlock front axle. I carefully reinstalled the front differential actuator. Before tightening and sealing it up I tested the 4hi button in neutral with key on. Transfer case shifted to 4wd with strong actuator sound and the front differential locked the axle crisp and firm. Many many attempts at in and out of 4hi. THE DASH LIGHT STILL BLINKS WHEN 4hi button is in. Goes off when 4hi button is out. Lower truck and drive it home with the blinking 4hi light. Test to see if it will go in and out of 4hi and it does several times.
4lo button has no response whatsoever because the light for 4hi is still blinking. It thinks it is not locked in. However it is locked in. Will it stay there? Who knows?
Anyone know where the solenoid is near passengers side?

AL

 

Yama
What would you consider a reset? Disconnecting the battery? Disconnecting the wires to the actuators(front n differential)? Or removal and reinstallation of both actuators?

AL

 

ECU?