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Discussion Starter #1
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!
 
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