Late Model Tacoma 4WD Actuators Failing

[CLynn85]

I've seen rumblings here and there on other sites, and I've been having trouble with my 2007 with 135k miles reliably engaging/disengaging 4wd. Curious to see if anyone here has had similar issues. I've pulled the cover off the T-case actuator and nothing looks corroded or awry, haven't gotten to the front diff yet.

Hate the thought of taking it in to the dealer for this. I also hate the fact that I'm having difficulties with something that I frankly don't even need. Why do I need a button to do what I've always used a lever for?

 

[Brandon H]

Had mine replaced (front). Was having problems going into 4hi (blinking light) . If that's what it's doing, it's for sure the add actuator. It's a problem on these trucks

 

[CLynn85]

What was the damage ($$) if you don't mind me asking? Good sanity check if I do take it into the dealer. What year and how many miles?

 

[timber]

For sure check the front diff actuator, they are known to go bad. I replaced one at 55k on my 2007. i bought it online from a toyota parts place back east somewhere? cant remember the name now but it ran $250ish last year for a new oem part. The transfer case will not shift to 4wd without the front diff engaging first. You can jack up one front wheel and turn your switch to 4hi and if you can still spin the wheel that's up your add is not working. It is not really a big job to swap it out.

 

[1911]

The front diff actuator is a weak design IMO, and has been known to fail. Here is a link to an article I wrote on another forum on how to replace one but also how to repair one (if the electrical contacts for the drive motor are bad, which is frequently why they fail).

http://www.fjcruiserforums.com/forums/transmissions-transfer-cases-traction-aids/90975-front-differential-actuator-repair-replacement.html

 

[2025 deleted member]

Excellent write-up. I was hoping our manual shift t-case fj's were immune to this problem. But I was wrong.

The front diff actuator is a weak design IMO, and has been known to fail. Here is a link to an article I wrote on another forum on how to replace one but also how to repair one (if the electrical contacts for the drive motor are bad, which is frequently why they fail).

http://www.fjcruiserforums.com/forums/transmissions-transfer-cases-traction-aids/90975-front-differential-actuator-repair-replacement.html

 

[zolo]

Nope the ADD fails on the FJs also. Ive replaced mine twice, Rebuilt one for a friends FJ.

They break contact for the motor. Can be repaired and used for a trail spare.
I have an FJ Tcase in my 06 Tacoma. Solved the button/switch issue now I have a manual FJ lever and a momentary switch for the front diff. seems to work well with a Good ADD actuator.

It is indeed a weak link. First time it happened on my truck the dealer fixed it. Would have been around $615.

Stupid simple to change though. And you can go ahead and change diff fluid while your at it.

 

[CLynn85]

Guess I'll try and drop the skids and pull the plastic cover and take a look-see tomorrow, thanks for the great writeup 1911!

 

[Martinjmpr]

Here's a dumb question:

If I understand correctly (and maybe I don't? ) the ADD does the same thing that locking hubs used to do, that is, it disconnects the wheels from the drive mechanism in the axle so that when you are in 2wd and the front driveshaft is not turning, the front wheels can spin freely without having to also turn all the metal in the differential and axle shafts, right?

The idea being that with less metal turning there is less wear-and-tear on the front axle and better MPG from having less drag due to moving parts not moving.

But locking hubs can simply be left in the "locked" position, too (or they can be removed entirely - for example, until the M-1008/1009/1028 CUCV were introduced, the US Military never used locking hubs on their 4x4s. On the early Jeeps, Dodge 1/2 and 3/4 tons and other military 4x4s, the front axle turns all the time, even in 2wd and the military just accepts the additional wear-and-tear or MPG loss.)

So my dumb question is this: If you're having trouble with the ADD, is there any reason you can't simply remove the mechanism entirely and just leave the front end "locked", even in 2wd? Aside from minimal wear and maybe a MPG or so, what would be the down side to this? Honestly, I have had 3 Toyotas with ADD since 2007 and I've never had a lick of trouble with any of them, but if I did, I'd be tempted to just pull the damn thing out altogether.

Along the same line, am I correct in assuming that the full-time 4x4s like the 80- and 100-series LCs, the V8 4runners and the manual-tranny FJ Cruisers don't have an ADD? Because with no 2wd capability, why would they need one?

So the thing about locking hubs is

 

[2025 deleted member]

I think it just leaves the right side unlocked when not activated. Kinda like having a locking hub on the right side only if I understod that correctly.

 

[Martinjmpr]

I think it just leaves the right side unlocked when not activated. Kinda like having a locking hub on the right side only if I understod that correctly.

I think I've heard that as well, which, again, makes me wonder if it would be possible to just ditch the system entirely? Seems to me the loss in performance and MPG, or the gain in wear, such as it is, would be minimal.

Now, I wouldn't do it on my '07 until and unless I started having problems with it (and I reiterate that on 3 different Toyotas - my 04 Taco, my 99 4runner, and my current 07 4runner, I've never had a lick of trouble with the ADD.)

But if I was putting together an around-the-world vehicle, I would certainly consider removing it as it would be just another potential point of failure.

 

[1911]

I think it just leaves the right side unlocked when not activated. Kinda like having a locking hub on the right side only if I understod that correctly.

That is correct; the operation of an open diff means that hardly anything is turning inside the diff when one side is disconnected.

As far as doing without, all that would be required would be to fix the sliding sleeve of the ADD mechanism in the engaged position, but you can't just remove the whole thing. Well, you could replace the whole front diff housing with one from a manual-transmission FJC, but most people would not find that economical. The cheap and easy way is to remove the ADD actuator from the diff housing, manually slide the splined connecting tube to the engaged position, turn the little electric motor for the shift fork in the actuator until the shift fork matches the groove for it in the connecting tube, disconnect one of the motor power leads, and re-install the actuator back on the diff. Then it will be permanently in the 4WD position, the 4WD ECU will still see the wiring harness connected, and you can shift the transfer case to 4WD any time on the fly.

 

[zolo]

Here's a dumb question:

If I understand correctly (and maybe I don't? ) the ADD does the same thing that locking hubs used to do, that is, it disconnects the wheels from the drive mechanism in the axle so that when you are in 2wd and the front driveshaft is not turning, the front wheels can spin freely without having to also turn all the metal in the differential and axle shafts, right?

The idea being that with less metal turning there is less wear-and-tear on the front axle and better MPG from having less drag due to moving parts not moving.

But locking hubs can simply be left in the "locked" position, too (or they can be removed entirely - for example, until the M-1008/1009/1028 CUCV were introduced, the US Military never used locking hubs on their 4x4s. On the early Jeeps, Dodge 1/2 and 3/4 tons and other military 4x4s, the front axle turns all the time, even in 2wd and the military just accepts the additional wear-and-tear or MPG loss.)

So my dumb question is this: If you're having trouble with the ADD, is there any reason you can't simply remove the mechanism entirely and just leave the front end "locked", even in 2wd? Aside from minimal wear and maybe a MPG or so, what would be the down side to this? Honestly, I have had 3 Toyotas with ADD since 2007 and I've never had a lick of trouble with any of them, but if I did, I'd be tempted to just pull the damn thing out altogether.

Along the same line, am I correct in assuming that the full-time 4x4s like the 80- and 100-series LCs, the V8 4runners and the manual-tranny FJ Cruisers don't have an ADD? Because with no 2wd capability, why would they need one?

So the thing about locking hubs is

If you were to remove the ADD and try to leave it in the locked position you would have to fabricate something to keep it there.
Its simply a sleeve on a slide. So if there is not a part to keep it either locked or unlocked it could simple slide the other way.

As for locking it Id say that could pose issues on the tarmac as both front wheels would be getting full traction and the diff would have a hard time slipping the wheels when turning.
So it has to be able to be unlocked and locked. I'm not sure if the Manuel FLC is the same or how they make that system work.
I know that in a 4wd 05+ Tacoma when in 4wd hi or low on Tarmac the system binds like crazy. I guess it could be the tcase but I doubt this cause I have an FLC tcase in my Tacoma and I have 2wd low and it never binds when the front diff is unlocked.
So it has to be the locked front diff. The ADD has to be selectable, it sure doesn't like turning on tarmac when engaged.

The design for the 05+ Tacoma has a fault were the Solder breaks at the motor. Can be repaired pretty easy. The internals are are still good, The motor simply gets no power cause the electric motor solder joint fails. Its all plastic and sorta crappy parts inside but they work, if the joint is good. I took mine apart and re soldered it to be sure it didn't fail again.

 

[1911]

As for locking it Id say that could pose issues on the tarmac as both front wheels would be getting full traction and the diff would have a hard time slipping the wheels when turning.

No it wouldn't, that is what a differential does - it allows either wheel to turn at a different rate from the other. Both wheels never get full traction, unless you had an ARB air locker installed and engaged.

I'm not sure if the Manuel FLC is the same or how they make that system work.

The manual-transmission FJC does not have the ADD mechanism; both front half shafts are always connected to the front diff, and the front drive shaft is always turning (it is full-time 4WD). It does have a center diff so that slight differences in traction between the front and rear don't cause driveline bind, but in models with ADD and part-time 4WD the front drive shaft isn't turned until you shift the transfer case into 4WD so there is no bind on pavement in 2WD even with the ADD slider permanently engaged.

 

[zolo]

No it wouldn't, that is what a differential does - it allows either wheel to turn at a different rate from the other. Both wheels never get full traction, unless you had an ARB air locker installed and engaged.




The manual-transmission FJC does not have the ADD mechanism; both front half shafts are always connected to the front diff, and the front drive shaft is always turning (it is full-time 4WD). It does have a center diff so that slight differences in traction between the front and rear don't cause driveline bind, but in models with ADD and part-time 4WD the front drive shaft isn't turned until you shift the transfer case into 4WD so there is no bind on pavement in 2WD even with the ADD slider permanently engaged.

Well Ive had my Tacoma bind on Tarmac in 4wd HI. When turning at a close to full lock. Go try it. I bet it will bind on your truck also.
I'm saying that if you keep the ADD locked all the time it would cause an issue.

If the front diff on an open diff front Tacoma is engaged it binds. That is all I'm saying.
I know what a differential does.


I see what your saying that if the ADD is engaged on the front diff in 2wd it will not bind. I suppose I see your point now. I kept thinking of how it acts in 4wd hi or low, The system hates to turn on tarmac. But if there is not power from the drive shaft I guess it would work just fine.

I eat my words my friend.

I guess since I have a manual FJ case I could try it out. I can just engage the front diff and go drive it in 2wd. My Tacoma is all manual tacse and what not. I can find out pretty easily..