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I removed the vacuum hose from the transfer case actuator nipple and it was dry-cracked badly, no way it was sealing. Trimmed 1/2" off the end of the hose to get nice clean rubber, put it back on the actuator nipple, and blammo 4hi was back in service.
I'm bumping this thread because I just fixed 4LO in my 05 Sequoia this way. The vacuum line ran between the actuator and the transfer case then wrapped around the actuator to form a hard 90 degree angle where it connected. The hose literally just fell off when I touched it. The end was split so I trimmed it and I wrapped it around the electrical harness twice instead of around the actuator; this way it connects straight on instead of at an angle.

I started up, put it in neutral, and hit the 4LO button. I didn't think it worked because it just went into 4HI, so I hit it again and 4LO engaged right away!

Just wanted to share. Thanks.
 

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Just a note of caution...I have a 2005 Sequoia and the ADD actuator is behind the front axle and I could not remove the cover without removing the actuator.

CAUTION: when I tried to remove the vacuum hose, the plastic nipple on the actuator cap broke off.:( I tried to epoxy it back on, per another post, but to no avail. In the end I had to remove the actuator (requiring a change of differential fluid and a new rtv silicon gasket) epoxy the nipple hole closed and modify a brake adjustment barrel for a bicycle to create a new nipple for the vacuum hose and drill a new hole for my "new" nipple.

It saved me $250 for a new actuator but it was a pain to fix a little broken nipple.
 

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I worked up the guts tonight to try this fix.. the process was a simple enough but it didn't fix anything. My 4WD light is still flashing.

When I took the motor cover off, here's what I found, the grease fluid surprised me. Is this what it should look like?

2012-03-15 20.51.09.jpg 2012-03-16 10.06.30.jpg

I cleaned the grease off of both the cover and the prongs on the spindle. I didn't find any corrosion on this cover once I wiped the grease off.

At this point I'm looking for another possible cause. I tested the actuator solenoids on top, they work fine. Any one have more ideas?

One other question I have.. should the differential button (to the left of the steering wheel) click when I press it in? Mine just seems to be a soft button that has no apparent 'on' or 'off' position. Any ideas?

One note, when I shift the 4WD lever into 4L mode.. it seems like the vehicle drives differently than 2WD. It acts like it is in 4WD.. it kind of crawls and and lurches.. but I tried driving up a steep incline and the front wheels never tried to spin. (EDIT: This must be 2WD LO mode?)

Thanks.
 

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My 06 did the same exact thing thing in December, I had to have the shift actuator in the transfer case replaced... works great now... $2,200 later.
 

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Yeh, mine is an 02 4Runner Sport and it's had the front actuator replaced. I'm just trying to avoid dropping that amount of money here and hoping there's something with the differential switch/system or something else I can troubleshoot.

Dubbya, did you have it fixed at a dealership or somewhere else?

Also, has anyone tried going to salvage yard and getting a new cover? I've read that you test the actuator by applying 12v to pins in the electrical connection.. but it seems if that doesn't work, it must be something in the cover that's bad. Am I wrong with this idea?
 

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I am new to this site and want to start for bye thanking everybody for sharing information on this. In the end I think I saved A bundle after
getting a basis of information on this T.S. I have A 2006 limited tundra four door. After reading a couple threads I built up enough knowledge to go after it!
My Original problem was both lights 4hi/4lo would not stop blinking. Went through procedure of shifting out of 4Hi as I have many times before. Still would blink
non stop both lights. Took to toyota they said they were able to get lights to stop blinking and get front actuator to actuate and get of gear. But I was still engaged on the rear axle. I told them I would bring it back monday (this was friday). On sunday I decided to have a look and I was very happy to have found the problem. Turns out vaccum hose on rear actuator was very deteriorated. Removed bolts (think 10mm) there was water, rust on current path. Cleaned off rust with
dremel bit (they make a couple perfect bits for this). Added little dielectric insulator, cleaned up connections at molex plug. My favorite part off-road test drive.
Works like a champ. IMG_0515.jpg IMG_0513.jpg IMG_0514.jpg
 

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Another 4WD Actuator Fix

This thread was a major help in running down my 4WD problems, thanks to all who posted.

About a month ago my 4WD light started flashing when I tried to disengage 4WD. 4WD Hi & 4WD Lo both worked but I had fits getting it out of 4WD.

I talked to two local shops about the problem, neither had ever come across a Tundra 4WD issue.

The root problem was the cracked vent tube, see #26, which allows water into the electrical housing. That water combines with the yellow grease to form a non-conductive crud over the concentric rings of the cover. No conduction, no motor, no 4WD Engage/Disengage. Many have referred to the rubber tube as a vacuum line, I could find no logic to suggest it's a vacuum line, no vacuum motor or piston anywhere. That said, I don't know why a vent is needed either.

If you're lucky you can remove the cover, clean off the crud from the concentric rings, reinstall and viola 4WD Engage/Disengage.

If you're unlucky you can remove the cover and the drive wheel will fall out, nothing holding it except friction, and your problems have just begun. I could not get the fine spline of the geared wheel inserted into the floating pinon gear.

The only solution I could come up with was to remove the pinon gear before installing the 4WD actuator assembly, bolt the 4WD actuator assembly to the transfer case, drop the pinon gear onto the small shaft spline at the same time aligning with the rack, then reinstalling the triangle cover.



In case you're wondering, the two switches drop into the two notches on the back side of the rack to provide position logic to the 4WD control computer in the engine bay. If they're not happy, the dash 4WD light will flash.

The official Toyota repair manual only mentions the 4WD actuator assembly, zero details. You are expected to replace the entire 4WD actuator assembly if problems.

Hope this helps someone.
 

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Re: Another 4WD Actuator Fix

Thanks for the nice pictures of the actuator assembly. I've been struggling with getting my 2004 Tundra into 4WD for months now. I *usually* try to put it into 4WD once a month, but I typically wait for rainy days to do so. Unfortunately, I forgot to do that for a few months over the summer, and when I tried it a couple months back, no dice. I've tried off and on for the past 3 months to no avail.

I tried the tips I've seen but so far I'm still SOL. I've tried tapping the actuator, checked all the fuses, I do hear the relays clicking on the passenger side where that ECU seems to live. And just now I removed the rear actuator cover to see if there was any visible corrosion. The vent tube was fine, and inside was all good... o-ring was solid, the grease was still good in there, no rust on the contacts.

I did try rotating the gear wheel by hand and I could do about a quarter turn either way... I'm really not sure how much that thing would rotate in order to engage 4WD though. Of course in my fiddling, the gear wheel did fall out, and as the above post mentions, I had a heckuva time getting it back in properly. I found that if I pushed it in and turned it a little back and forth, wiggling and pushing, I finally got that inner gear to re-engage inside, however it fits. I lost a little bit of fluid when the wheel came out, but no more than a teaspoon worth, or two. Just FYI for anyone else who's curious to poke in there, if you're worried about losing some fluid. Just in case, have something to catch any drippage.

I put it all back together, and odd are I didn't have the wheel in the same position as before, so at first both the hi and lo lights were flashing at me. I just popped into neutral, turned 4WD off (it was on before, although not engaging), and that turned off both lights. It probably managed to turn the wheel to whatever normal position, which probably means that actuator is working okay. I was going to pull the cover again and see where it was now, but I was getting a little tired of dealing with it by that point. :)

Now I think it may be that front actuator (the ADD or whatever). I see it, but it seems really hard to get to. I felt the vent tube and connections on it and they feel okay, no cracking or damage that I could tell.

I even tried the technique of going into reverse with the wheel turned hard right or left... the neighbors probably thought I was drunk the way I was wheeling around our cul-de-sac doing odd turns in reverse... but the end result was still a flashing 4HI whenever I try to engage. :(

At this point I may have to bite the bullet and take it in for service... there's a nice place I've taken it to before for work and they have better prices than the stealerships, but then again this thing is just over 150K miles and maybe it's time to let the dealership give it a full spa package of love and some 4WD work on the side. Winter is coming... I want my 4WD working!
 

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Re: Another 4WD Actuator Fix

...Now I think it may be that front actuator (the ADD or whatever). I see it, but it seems really hard to get to. I felt the vent tube and connections on it and they feel okay, no cracking or damage that I could tell....
Well, how about that. I had some extra time today, so I crawled under the front and tapped on the front actuator ADD with a hammer... just some light tapping, and since it's kind of in a weird spot, I was only able to tap a bit on the front of it and a bit on the rear. I'm not sure where exactly would be best, but apparently it was enough!

Now, the tapping was with the truck in neutral and idling, 4HI button pushed in but flashing. During the tapping itself nothing changed, but when I hopped back in and toggled the switch off and back on again, boom, it went right in and engaged 4WD. Awesome!

I tooled around for a couple miles and even stopped, went into neutral, and put it in 4LO for a few dozen feet. The first time after going into 4LO, when I switched to drive it made a horrible noise, so I went back to neutral, turned off 4LO, went to drive, back to neutral, and then tried 4LO again. That time it went into drive fine, so it may have just been a little finicky. I hardly ever use 4LO (I think this was only the 3rd time I'd ever used it!) so I don't know if that's normal.

Anyway, 4HI is working now... tapping that *front* actuator was the key to it. At least I got to explore underneath and tinker with a few things I don't normally do, like checking out that rear actuator/position switch. But maybe this will encourage others who have the flashing 4HI problem. Tap on that front one a bit and give 'er a shot.
 

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Re: Another 4WD Actuator Fix

Thanks for the nice pictures of the actuator assembly. I've been struggling with getting my 2004 Tundra into 4WD for months now. I *usually* try to put it into 4WD once a month, but I typically wait for rainy days to do so. Unfortunately, I forgot to do that for a few months over the summer, and when I tried it a couple months back, no dice. I've tried off and on for the past 3 months to no avail.

I tried the tips I've seen but so far I'm still SOL. I've tried tapping the actuator, checked all the fuses, I do hear the relays clicking on the passenger side where that ECU seems to live. And just now I removed the rear actuator cover to see if there was any visible corrosion. The vent tube was fine, and inside was all good... o-ring was solid, the grease was still good in there, no rust on the contacts.

I did try rotating the gear wheel by hand and I could do about a quarter turn either way... I'm really not sure how much that thing would rotate in order to engage 4WD though. Of course in my fiddling, the gear wheel did fall out, and as the above post mentions, I had a heckuva time getting it back in properly. I found that if I pushed it in and turned it a little back and forth, wiggling and pushing, I finally got that inner gear to re-engage inside, however it fits. I lost a little bit of fluid when the wheel came out, but no more than a teaspoon worth, or two. Just FYI for anyone else who's curious to poke in there, if you're worried about losing some fluid. Just in case, have something to catch any drippage.

I put it all back together, and odd are I didn't have the wheel in the same position as before, so at first both the hi and lo lights were flashing at me. I just popped into neutral, turned 4WD off (it was on before, although not engaging), and that turned off both lights. It probably managed to turn the wheel to whatever normal position, which probably means that actuator is working okay. I was going to pull the cover again and see where it was now, but I was getting a little tired of dealing with it by that point. :)

Now I think it may be that front actuator (the ADD or whatever). I see it, but it seems really hard to get to. I felt the vent tube and connections on it and they feel okay, no cracking or damage that I could tell.

I even tried the technique of going into reverse with the wheel turned hard right or left... the neighbors probably thought I was drunk the way I was wheeling around our cul-de-sac doing odd turns in reverse... but the end result was still a flashing 4HI whenever I try to engage. :(

At this point I may have to bite the bullet and take it in for service... there's a nice place I've taken it to before for work and they have better prices than the stealerships, but then again this thing is just over 150K miles and maybe it's time to let the dealership give it a full spa package of love and some 4WD work on the side. Winter is coming... I want my 4WD working!
I agree that it sounds like your transfer case actuator is working. One way to check would be to pull the front driveline and see if the ouput is turning. Of course you would either need to also pull the rear driveline so that the vehicle doesn't move, or jack the entire rear end off the ground. Just a thought.

My friend is having the same issue with his '04 4Runner Sport. Two different rigs, but it has given me some things to check under there. Thanks everyone!
 

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This is one of the best threads I've seen on the 4WD system; excellent work, gentlemen.

Tapping on the actuator may have been enough to dislodge a stuck fork. The automatic system is "use it or lose it"...factory recommendation is 10 miles monthly in 4WD, and don't forget to shift in to low range a few times. Wet pavement in a straight line will do, if you don't have access to a low-traction surface (dirt, snow, ice).

Realistically speaking...it's really just a matter of keeping the system lubricated and moving, so if you have a mile or two of wet pavement, all you really need to do is bump the button a few times, and drive far enough to rotate the gears in the front diff and throw some oil around, same with the planetary gear and associated shift mechanism in the transfer case. Having an excuse to find 10 miles of 4WD trails is really just a bonus ;).

-S
 

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...I tested the actuator solenoids on top, they work fine. Any one have more ideas?
csnoke (or anyone else on this very helpful thread)-
Can you tell me how you tested those position switches on the transfer case? I have a thread that I've been trying to track down a 4WD actuator problem, but can't figure it out...and I really don't want to throw away an otherwise good transfer case if it's just an electrical problem. Thanks!

Thread is here:
http://www.tundrasolutions.com/forums/t-case-driveshaft-diff-axle-hub/289954-2001-tundra-4wd-light-blinks-but/#post2331489
 

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Re: Another 4WD Actuator Fix

This thread was a major help in running down my 4WD problems, thanks to all who posted.

About a month ago my 4WD light started flashing when I tried to disengage 4WD. 4WD Hi & 4WD Lo both worked but I had fits getting it out of 4WD.

I talked to two local shops about the problem, neither had ever come across a Tundra 4WD issue.

The root problem was the cracked vent tube, see #26, which allows water into the electrical housing. That water combines with the yellow grease to form a non-conductive crud over the concentric rings of the cover. No conduction, no motor, no 4WD Engage/Disengage. Many have referred to the rubber tube as a vacuum line, I could find no logic to suggest it's a vacuum line, no vacuum motor or piston anywhere. That said, I don't know why a vent is needed either.

If you're lucky you can remove the cover, clean off the crud from the concentric rings, reinstall and viola 4WD Engage/Disengage.

If you're unlucky you can remove the cover and the drive wheel will fall out, nothing holding it except friction, and your problems have just begun. I could not get the fine spline of the geared wheel inserted into the floating pinon gear.

The only solution I could come up with was to remove the pinon gear before installing the 4WD actuator assembly, bolt the 4WD actuator assembly to the transfer case, drop the pinon gear onto the small shaft spline at the same time aligning with the rack, then reinstalling the triangle cover.



In case you're wondering, the two switches drop into the two notches on the back side of the rack to provide position logic to the 4WD control computer in the engine bay. If they're not happy, the dash 4WD light will flash.

The official Toyota repair manual only mentions the 4WD actuator assembly, zero details. You are expected to replace the entire 4WD actuator assembly if problems.

Hope this helps someone.

Does anyone know if it's possible to take the differential actuator off without disassembling the differential! My motor on actuator gets warm after trying to engage and disengage a few times, so I'm assuming the motor is working and everything electrical works. I'm guessing the gears are jammed. I can't tell from this post and pictures if you just unbolt and you can pull the whole actuator off to examine all gears and shaft. Any input is appreciated!!
 

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Re: Another 4WD Actuator Fix

This is just a big thank you to everyones input. I also have(had) 2002 Tundra front actuator problem. Same symptoms: flashing light,no engagement,etc. Very scary if you love your 4*4. The tap on the actuator and unplugging and replugging all the connections to both actuators seem to do the trick for me as well. Very easy fix.
 

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same for me, 4 hi flashing, and not engaging.. 04 tundra..I took off plug (wiring) from actuator, I was Going to remove screws, but my screwdriver was not going to work ,and it started to rain, so I plugged it back in for another day, tried it out again anyway , worked great, I got lucky and it was just a bad connection on the front connector. Try this first
 

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I have read this entire thread and have attempted to do most of the procedures as described. I have a 2003 Tundra and am experiencing the same 4Hi blinking light without any engagement of the 4 wheel drive. I looked at both vacuum hoses of the front and rear actuators...the rear one was cracked at the nipple of the housing. "cool, easy fix", I thought. Trimmed off the bad section and replaced. No engagement. Light still blinks. I removed both of the electrical connectors and cleaned them with a CRC electrical component cleaner and then put dielectric grease inside and reconnected. No change. I had my daughter push the 4Hi button while I was underneath the vehicle and could both hear and feel the actuator moving inside both housings. Both prior and after any of these attempts at repair I put the truck in reverse and drove backwards on dry pavement both directions. More than once. (I looked kinda foolish in the Home Depot parking lot driving in circles backwards). I sprayed PB Blaster on the bolts on the rear actuator housing and on the Philips head screws on the front housing about 15 minutes prior to trying to get them out. I was able to easily remove two of the three bolts on the rear actuator and the third snapped off about 3/4 of the length of itself. I was still able to remove the housing and take a look inside. Based upon what I read above I was expecting the inside to have water, dirt and corrosion since it was the one that had the cracks in the vacuum hose. Nope. Clean and dry with a yellow grease pretty well covering where it seemed it should be. It did have a slight crust over it but no discoloration or dirt. The crust seemed to be slight oxidation? I attempted to remove the broken end of the bolt with a pair of visegrips but it was majorly stuck. I'll get to that later hoping that I don't have to drill it out. The large O-ring sealing off the the housing from the weather and road grime seemed to be in pretty decent condition. The front actuator housing Philips head screws were not so easy and I could not get them off to take a look inside even though they had been DB Blastered almost an hour at that point since I worked on the rear one first. So...a question. Is there something I'm missing since it seems that both actuators are moving when the button is pushed and yet there is still no 4 wheel drive. The truck is my landowner's and was never really well maintained but the 4x4 worked last summer (2014) all the way through about Feb or so this year. It worked intermittently for about a month and then not at all by end of March. Luckily we had minimal snow here near Durango so I was able to get away with it figuring I'd deal with it this summer. So here I am and not sure where to go next.

*******Realized I had not attempted to give a few good knocks on the actuators to see if that might help them engage. Particularly the front one. I will also note that I have not checked fluid levels of the transfer case so will head out to give that a check as well. Wondering if there might be a better grease (dielectric perhaps???) to replace the original yellow grease that was inside the rear actuator. I'm hoping I don't have to remove the cover of the front actuator just because the screws are so firmly stuck that I don't want to strip the head. Thanks for some insight if you have some.******
 

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Was just about to R&R the 4wd activators on the front diff and X-fer case when I saw the comment from the service writer, activate 4-hi, steer hard left or right, and before I could put it in reverse it clanked loudly and the light came on steady. I rolled it and could tell it was in 4wd. Disengaged and reengaged several times in neutral and was able to go to 4-lo. All this after almost two years of no 4wd.

Thank you TundraSolutions members.
You're the best.
 

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This thread has really saved me!!!! i tried the reveres with wheels turned, no joy. 4HI continued to flash. Went to dealership and priced the actuator cap, vacuum line, and front diff actuator cap. Came home, and took a look under my truck and the vacuum hose was cracked and completely off the actuator cap. Trimmed the line and secured with a small zip tie. BOOM, problem solved!!!! Thank you Thank you Thank you!!!! It's really a shame how much money people are spending for something that can be fixed by an amateur DIYr like myself. My vehicle is a 2007 toyota sequoia 4x4 SR5. 4X4 system works flawlessly now. Preparing to tackle transmission, transfer case, and differential fluid change!
 

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I own a 2001 Sequoia and for the past couple of years I have had difficulty getting into 4wd so I knew it was just a matter of time and that time came yesterday. I too got the dreaded flashing light with no engagement... or so I thought. After driving across town I realized that the front wheels were locked together even though I was not in 4 low. After trying all of the tricks mentioned above to no avail I crawled underneath and removed the cover and contents of the rear actuator - I got lucky and only twisted off one screw. I found a little moisture inside so I disassembled the motor assembly and cleaned up the armature with emery cloth. After drilling out the broken screw and tapping new threads I reassembled everything and put it back on the Sequoia. I was still unable to get the unit to work so I moved to the front unit, referred to as the ADD unit. It is much more difficult to get to as it's above the axle and below the oil pan with the steering rack in the way too. I removed the entire unit as it uses a fork to move the gear that locks the front end. I put this in the vice and twisted off two screws which I had to drill and tap. The motor showed little wear so I did nothing with it and reinstalled the unit but moved the fork to the right as to unlock the front end. I did not reconnect the wiring harness because after all that I didn't want the unit to lock back up.
After 5 hours work and not finding a solution I found a video on YouTube at this link. I am going to check the two switches on the rear actuator next then go from there.

https://www.youtube.com/watch?v=NPPQn0E8ThM
 

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My 04 DC was doing the same thing, just flashing. My buddy put it on a lift while in drive and at idle the front and rear shafts were moving so he knew it was coming from the ADD. We proceeded to unbolt the 4 bolts from the unit and took a little finesse to get it out due to power steering plumbing and all. Once removed, we took it to the bench and totally disassembled it. The motor looked new and the brushes were not worn at all. The grease had become rather waxy in texture, so we cleaned all of it out and relubed it with dielectric grease. The contacts and tracks were shiney as can be with no corrosion. We put it all back together and let it dangle from the harness on the truck as we engaged the 4-Hi and the fork moved. What a relief. We bolted it back on and applied gasket sealant before topping off the diff fluid. Works like a charm now. Very relieved. I don't use 4x4 very much here in WV, and it was by accident that I hit the 4x4 button and noticed it flashing before we had a winter storm. I will from now on engage the 4x4 on loose gravel for a few miles to keep everything functional
 
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