Late Model Tacoma 4WD Actuators Failing

[zolo]

1911, You are not as easily confused as I am apparently.

I just tried it with my truck left in 2wd. No bind with front diff ADD turned on. I guess that is a good advantage of ditching the Tacoma electric tcase.
If the ADD fails again on my truck I can get it back into 2wd and drive normal. I learn something new everyday.

still 2wd Low is the best gain for that swap.


I guess with what Martinjmpr is saying or asking would not work if you still had the Tacoma tcase.
Since it switches into 4wd based on the ADD moving the diff into engaged position. You would never get the tcase to work right if the system was all stock and the ADD was engaged all the time the tcase would be stuck in whatever position it was in until it recognized the ADD was moving and working correctly.

 

[Martinjmpr]

Zolo: I think we're talking about two different things here.

When you shift the T-case into 4-hi, it sends power to the front driveshaft, which then sends it to the front wheels wheels through the front diff. It's the T-case that gives the vehicle the 4wd capability.

The ADD does not put the vehicle in 4wd. All the ADD does is allow the front wheel (the one on the right side only, apparently?) to spin free from the front axle when the vehicle is in 2wd.

As I said above, there are plenty of vehicles out there that don't even have this capability. For example, the TJ-series Jeep Wranglers. The older YJ's had a vacuum-operated ADD like the 4runner/Taco, and it proved to be problematic (hey, it's a Jeep thing, I guess. ) So when they redesigned the TJ for 1997, they just dropped the ADD altogether. So on a TJ series Jeep, when you are driving down the paved road in 2hi, the front axle is turning. It's not getting power from the engine (because the T-case is still in 2wd and not sending power to the front axle) but the action of the wheels turning is causing the front diff to spin. Jeep just accepted this additional wear as part of the price for the reliability of having a system with one less failure point.

So, being without an ADD would not cause the driveline to bind as long as you kept the T-case in 2wd. It wouldn't bind because even with the ADD engaged, there's still no power going to the front wheels.

Now, if what you're saying is that the ECU would be confused because it would "see" the ADD as engaged while the T-case was in 2-hi, you may have a point, but I don't know what effect that would have on driveability. I would think that maybe you could put a jumper or something else on the ECU sending unit to trick it into thinking the ADD was not engaged or perhaps you could just make it so that the ECU doesn't "see" the ADD system at all.

 

[Martinjmpr]

Elaborating just a bit, my concern (when reading this thread) was that the electrical actuator for the T-case (NOT the ADD) was failing. Since the 05+ Taco and 03+ 4runner both have an electric dial for the 4wd, the action of actually shifting the T-case into 4wd is done by an electric motor. If this fails (as I understand it) it's a very expensive repair.

FJ Cruisers and older Tacos/4runners don't have this problem because they have a manual lever to shift the T-case into 4wd.

 

[zolo]

Zolo: I think we're talking about two different things here.

When you shift the T-case into 4-hi, it sends power to the front driveshaft, which then sends it to the front wheels wheels through the front diff. It's the T-case that gives the vehicle the 4wd capability.

The ADD does not put the vehicle in 4wd. All the ADD does is allow the front wheel (the one on the right side only, apparently?) to spin free from the front axle when the vehicle is in 2wd.

As I said above, there are plenty of vehicles out there that don't even have this capability. For example, the TJ-series Jeep Wranglers. The older YJ's had a vacuum-operated ADD like the 4runner/Taco, and it proved to be problematic (hey, it's a Jeep thing, I guess. ) So when they redesigned the TJ for 1997, they just dropped the ADD altogether. So on a TJ series Jeep, when you are driving down the paved road in 2hi, the front axle is turning. It's not getting power from the engine (because the T-case is still in 2wd and not sending power to the front axle) but the action of the wheels turning is causing the front diff to spin. Jeep just accepted this additional wear as part of the price for the reliability of having a system with one less failure point.

So, being without an ADD would not cause the driveline to bind as long as you kept the T-case in 2wd. It wouldn't bind because even with the ADD engaged, there's still no power going to the front wheels.

Now, if what you're saying is that the ECU would be confused because it would "see" the ADD as engaged while the T-case was in 2-hi, you may have a point, but I don't know what effect that would have on driveability. I would think that maybe you could put a jumper or something else on the ECU sending unit to trick it into thinking the ADD was not engaged or perhaps you could just make it so that the ECU doesn't "see" the ADD system at all.

That is what I'm saying. The Tacoma system has a 4wd ECU and the Tcase takes command when it see's the ADD engage.
If the ADD doesn't work right the Tcase will do nothing but flash at you in the dash indicating the 4WD is not working.

So if your truck is stock you would never be able to leave the ADD engaged, cause the tcase/4wd system would not work right.

Now on my truck (06 Tacoma) and here is were a lot of my own confusion comes in. Has an FJC tcase with manual controls so I have none of those ECU issues.

 

[skrillah]

Zolo: I think we're talking about two different things here.

When you shift the T-case into 4-hi, it sends power to the front driveshaft, which then sends it to the front wheels wheels through the front diff. It's the T-case that gives the vehicle the 4wd capability.

The ADD does not put the vehicle in 4wd. All the ADD does is allow the front wheel (the one on the right side only, apparently?) to spin free from the front axle when the vehicle is in 2wd.

As I said above, there are plenty of vehicles out there that don't even have this capability. For example, the TJ-series Jeep Wranglers. The older YJ's had a vacuum-operated ADD like the 4runner/Taco, and it proved to be problematic (hey, it's a Jeep thing, I guess. ) So when they redesigned the TJ for 1997, they just dropped the ADD altogether. So on a TJ series Jeep, when you are driving down the paved road in 2hi, the front axle is turning. It's not getting power from the engine (because the T-case is still in 2wd and not sending power to the front axle) but the action of the wheels turning is causing the front diff to spin. Jeep just accepted this additional wear as part of the price for the reliability of having a system with one less failure point.

So, being without an ADD would not cause the driveline to bind as long as you kept the T-case in 2wd. It wouldn't bind because even with the ADD engaged, there's still no power going to the front wheels.

Now, if what you're saying is that the ECU would be confused because it would "see" the ADD as engaged while the T-case was in 2-hi, you may have a point, but I don't know what effect that would have on driveability. I would think that maybe you could put a jumper or something else on the ECU sending unit to trick it into thinking the ADD was not engaged or perhaps you could just make it so that the ECU doesn't "see" the ADD system at all.

Good post... I didn't know that about the Jeep thing...

 

[Martinjmpr]

That is what I'm saying. The Tacoma system has a 4wd ECU and the Tcase takes command when it see's the ADD engage.
If the ADD doesn't work right the Tcase will do nothing but flash at you in the dash indicating the 4WD is not working.

So if your truck is stock you would never be able to leave the ADD engaged, cause the tcase/4wd system would not work right.

Now on my truck (06 Tacoma) and here is were a lot of my own confusion comes in. Has an FJC tcase with manual controls so I have none of those ECU issues.

Wait - so you have a FJC T-case on your Taco? So how does your ADD engage? Above you made it seem like you could engage your ADD independently of the 4wd control on the T-case (giving you the ability to put the T-case into 4-low but keep the ADD disconnected, in effect giving you 2-low) that must be something you rigged up yourself?

 

[zolo]

Elaborating just a bit, my concern (when reading this thread) was that the electrical actuator for the T-case (NOT the ADD) was failing. Since the 05+ Taco and 03+ 4runner both have an electric dial for the 4wd, the action of actually shifting the T-case into 4wd is done by an electric motor. If this fails (as I understand it) it's a very expensive repair.

FJ Cruisers and older Tacos/4runners don't have this problem because they have a manual lever to shift the T-case into 4wd.

This is a thread for the front diff ADD. Which fails a ton.

 

[zolo]

Wait - so you have a FJC T-case on your Taco? So how does your ADD engage? Above you made it seem like you could engage your ADD independently of the 4wd control on the T-case (giving you the ability to put the T-case into 4-low but keep the ADD disconnected, in effect giving you 2-low) that must be something you rigged up yourself?

Its the same tcase from a auto FJ to a Auto or 5spd Tacoma.
Just the FJ has a lever and the Taco has a big electric piece o crap on the back. My truck has a lever from an FJ right next to my trans gear shift. Looks factory
Its a fairly common swap.

It only takes wiring into the ADD with a 6 pole momentary switch.

Then you gain 2wd low, full manual control of the tcase and it can never mess with you again as for getting stuck in 4wd low or not engaging to low.

 

[Telcobilly]

This stuff makes me miss my old CJ7. Is there an aftermarket solution to make this manual and simpler?

 

[Dave Bennett]

110k + on my OE ADD actuator... Fingers crossed.

 

[Martinjmpr]

This stuff makes me miss my old CJ7. Is there an aftermarket solution to make this manual and simpler?

The FJC or similar 2 stick T-case is a solution, but it's kind of like using a sledghammer to swat a fly.

 

[1911]

This stuff makes me miss my old CJ7. Is there an aftermarket solution to make this manual and simpler?

Inchworm "Lefty" transfer case, which gives you low-range gearing that is really useful, plus you can pick up another 3-4" of ground clearance. Not cheap though...

 

[CLynn85]

Just wanted to follow up and add a few notes to what's already been said.

This afternoon (spilled over into evening) I repaired the ADD on my Tacoma. It has just shy of 135,000 miles on it in less than six years. It has not been abused but also hasn't led the life of a mall crawler either. It was not a fun process and I'm not really sure what I'm most irritated about. It could be a) the fact that it was so poorly designed in the first place, b) the fact that nothing in the front end of this truck is at all serviceable with a basic set of mechanic's tools, or c) the fact that the truck has as many electronic gizmos as a mid 90's BMW to do what a simple linkage/lever could've done.

For mine it was the contacts on the motor, one of the small plastic tabs that locates the motor failed and one pole of the motor was no longer making contact with the brass strips protruding from the plastic case. The motor was still securely fastened thanks to the metal band and 2 screws on the front, but the lack of solder on the contact allowed it to cease functioning. I soldered both poles of the motor and also soldered in the limit switch while I was in there.



A few things to note about the R&R (and I don't mean rest and relaxation):

1. In 1911's writeup (which was very informative and a great start, thank you!), it notes a 14mm hex driver for the rear mount. On my 2007 it was a 12mm. That may be a useless piece of information though because in my case it did not make any difference removing it due to the motion being restricted by everything else, so it could've been left as-is. Also, mine was a bit seized, and there's nothing to grab on the back side to keep this blind bolt in a bushing from spinning....******!

2. I could have removed the plastic housing/motor and repaired it without draining the diff and removing the entire actuator, if it weren't for the phillips screws. The most inaccessible one stripped despite using a lot of care, pressure, and patience. As a result I reassembled the unit with socket cap screws.

3. Vent hose apparently becomes brittle after 5 years, mine tore at the end of the nipple when removing, was able to snip off and reattach what was left, but there won't be enough slack to do that again.

4. Guess that's about it, plan to spend a couple hours and a lot of time going up/down with the jack on the diff housing, I found it easier to remove the upper screws through a small (and I mean small) gap between the crossmember and the power steering, but it took a lot of patience and several different combinations of sockets, extensions, and adapters.

 

[Glorybigs]

My buddy and I repaired my ADD today. It was not hard and I did not drain any of the diff fluid.

Symptoms included:
Would not lock into 4WD HI, 4WD indicator kept flashing.
The indicator would only shut off after I shut the vehicle off and tried it the next morning.
After multiple attempts in trying to get 4WD HI locked in, it finally did and then would not disingage...it just started flashing the 4WD indicator after I switched to 2WD HI.

Vehicle is a 2007 OR/AT Tacoma

Brought it to the shop, put it on the lift and took the following steps.
1. Removed engine skid.
2. Unbolted the front diff braces, leaving a single bolt in the rear brace (the one with a rubber mount on the drivers side).
3. Used a mono-jack to support the diff.
4. Removed the Philips head screws that hold the cover on the ADD. This was accomplished using a very long screw driver while adjusting the mono-jack to allow a straight shot with the screw driver. Unplugged the harness and CAREFULLY removed the hose from the vent tube.
5. Once the cover was popped off (it stays retained up on the ADD, it just comes lose enough to make this fix), I soldered the motor connectors to the brass contacts.
6. Put it all back together and it worked better than it ever has, it literally works better than when the truck was new. It locks and unlocks almost instantly.

I would strongly urge everyone to do this simple little upgrade. Mine went to **** when I was out in the middle of Death Valley last weekend. I got stuck in 2WD and thankfully I had friends with me to pull me back up onto the trail.

 

[Letsgomoreplaces]

ADD Axle Disconnect Actuators, Toyota Taoma, FJ Cruiser

Just FYI, We have lots of these in stock as Take-offs since we send our complete 3rd members without them:

We get asked all the time, but since these were not inventoried, not all our staff knew we had them. Tere are the part numbers. They are take-offs of used diffs, as we ship our 3rd members without them. There may be some cosmetic flaws.

Often referred to as “A.D.D” Disconnect, Axle Actuator, etc.
Link:
TOY41400-35032
Front Axle Disconnect Actuator & Axle Tube T8S, Toyota FJ Cruiser, Tacoma, 4runner (Take-off) $200


Or if you would like to do away with the Axle disconnect and go to a 1-piece axle and tube:
TOY41400-35032MAN
Toyota Front Non-Disconnect Axle Shaft & Tube T8S, Toyota FJ Cruiser, Tacoma, 4runner, AWD