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-   -   4wd not engaging on an '04 TRD V6 Doublecab (http://www.tacomaworld.com/forum/technical-chat/121103-4wd-not-engaging-04-trd-v6-doublecab.html)

tanstaafl26 10-31-2010 10:42 AM

4wd not engaging on an '04 TRD V6 Doublecab
 
Hi

I have the push button 4wd system on an 04' TRD V6 doublecab with the automatic transmission. When the button is pushed, I still hear the click of the switch, but the indicator light doesn't come on and the front wheels aren't powered. However, I can shift the lever into 4wd low and the rear diff lock will engage. My truck has 120,000 on it and a sizeable portion of that with 4wd engaged in the snow and in baja. I first noticed the problem last Christmas in baja but was able to get the system engaged by turning the system on and off while accelerating, braking and reversing. When it does turn on/engage, there's is no difference in the sound of the system as the button is pushed. Later in Mammoth, I tried the same routines, but it only came on after driving 5 or so miles. Any ideas? I tried a search but didn't see a thread with my equipment or specific problems. thanks for the help!

tanstaafl26 03-07-2011 04:54 PM

I haven't figured it out but thinking on the issues brings me to these further thoughts:

1) The 4wd engaged light doesn't come on when I push the button but low range will engage and my locker works. Will following the indicator light's switch in the 4wd system lead me to the problem? ie where is the switch that tells the system that it's actually in 4wd located?

2) Is it logical to assume that since I can get the truck into 4wd low range it means the transfer case is working? Could it be that I need to rebuild the front hubs?

3) General operation question-how does the 4wd system work? Does the button on the 4wd lever operate two seperate switches, ie the hubs and the tranfer case?

thanks

bajajoaquin 03-08-2011 08:25 AM

Hi, new here, but if I read his first post correctly, it sounds to me like the front wheels aren't getting power when it's in low range, but the transfer case is in it's low gears.

Yoytoda 03-08-2011 08:49 AM

Quote:

Originally Posted by PSU Taco85 (Post 2844922)
That's what I gather, the ADD actuator is probably bad.

this...

i think the 04s had vacuum actuated 4wd. maybe a vacuum leak, bad vacuum motors.

On my s10 the vacuum control switch on the tcase would go bad and not actuate the add. Another possibility

David K 03-08-2011 08:54 AM

Sounds like an ADD issue (Automatic Disconnecting Differential)... This is what our Tacomas have for shift-on-the-fly, like auto locking hubs. It is next to the front differential and is a device that inserts a fork onto the driveline to engage the front end whenever you push the 4WD button. If the vacuum operated fork isn't engaging, the truck will only be in 2WD, but you will have low range and a rear locker working because it will think it is in 4WD. The ADD has a breather next to the front differential breather, as well... here mine are, near the battery:

http://i213.photobucket.com/albums/c...1lights017.jpg

Yoytoda 03-08-2011 08:57 AM

Quote:

Originally Posted by David K (Post 2844958)
Sounds like an ADD issue (Automatic Disconnecting Differential)... This is what our Tacomas have for shift-on-the-fly, like auto locking hubs. It is next to the front differential and is a device that inserts a fork onto the driveline to engage the front end whenever you push the 4WD button. If the vacuum operated fork isn't engaging, the truck will only be in 2WD, but you will have low range and a rear locker working because it will think it is in 4WD. The ADD has a breather next to the front differential breather, as well... here mine are, near the battery:

http://i213.photobucket.com/albums/c...1lights017.jpg

FWIW our front add is no longer vacuum actuated. It solenoid actuated.

OP is driving an 04 so im not sure if he has the same system

David K 03-08-2011 09:03 AM

Thanks.. he should have it checked out regardless of how it works. I don't understand why is has waited so many months to fix his 4WD... I had an '01 Off Road 4WD, as well... with push button H4 on the joy stick. Never failed in the 5 years and 136,000 miles (many in Baja)!

Yoytoda 03-08-2011 09:05 AM

Quote:

Originally Posted by David K (Post 2844986)
Thanks.. he should have it checked out regardless of how it works. I don't understand why is has waited so many months to fix his 4WD... I had an '01 Off Road 4WD, as well... with push button H4 on the joy stick. Never failed in the 5 years and 136,000 miles (many in Baja)!

yea, i hear ya. Wasnt trying to bash your post or anything. just didnt want the op to go looking for a breather that potentially isnt there...

tanstaafl26 03-08-2011 09:29 AM

[QUOTE=David K;2844986]Thanks.. he should have it checked out regardless of how it works. I don't understand why is has waited so many months to fix his 4WDQUOTE]

Ah, well, that's easy: unemployement, no health insurance and newborn boy=no time & money for south of border/Tahoe missions and I'm not willing (Anymore) to risk bankruptcy for unpaid medical bills.

But a job and insurance have been aquired that so I'll look into the vacuum actuator. Thanks for the help!

David K 03-08-2011 09:35 AM

[QUOTE=tanstaafl26;2845083]
Quote:

Originally Posted by David K (Post 2844986)
Thanks.. he should have it checked out regardless of how it works. I don't understand why is has waited so many months to fix his 4WDQUOTE]

Ah, well, that's easy: unemployement, no health insurance and newborn boy=no time & money for south of border/Tahoe missions and I'm not willing (Anymore) to risk bankruptcy for unpaid medical bills.

But a job and insurance have been aquired that so I'll look into the vacuum actuator. Thanks for the help!

Understand all that.. been there myself... all will turn out fine!

Get the ADD looked at... Then go to Baja and have some fun!

tanstaafl26 03-08-2011 11:59 AM

[QUOTE=David K;2845106]
Quote:

Originally Posted by tanstaafl26 (Post 2845083)

Then go to Baja and have some fun!

I intend to! Need some fresh clam tacos and a cold Ballena Pacifco.

A vacuum leak makes sense as well as being less expensive than a transfer case. I'll crawl under this weekend and post when I figure it out!

tanstaafl26 03-20-2011 03:46 PM

1 Attachment(s)
It works! The vacuum line that seems to run from the top of the trans to the transfer case looked solid but wasn't. The end that plugs, more of a loose push really, onto the transfer case was somewhat loose and after pulling it off, the end was cracked. It doesn't have enough slack to trim and re-attach so I used a zip tie to tighten it down. When I pressed the button I could hear a hissing that I've not heard before and it took 8 or 10 pushes to get the light to come on. I might have more cracked hoses somewhere but it's working so far. Thanks for the advice!

Yoytoda 03-20-2011 09:45 PM

Quote:

Originally Posted by tanstaafl26 (Post 2902879)
It works! The vacuum line that seems to run from the top of the trans to the transfer case looked solid but wasn't. The end that plugs, more of a loose push really, onto the transfer case was somewhat loose and after pulling it off, the end was cracked. It doesn't have enough slack to trim and re-attach so I used a zip tie to tighten it down. When I pressed the button I could hear a hissing that I've not heard before and it took 8 or 10 pushes to get the light to come on. I might have more cracked hoses somewhere but it's working so far. Thanks for the advice!

if you go to napa you can get vacuum hoses for 20 cents a foot. bring in a piece of it to match the size.

tanstaafl26 04-12-2013 09:26 AM

Update (yes it's an old thread): The system went down again and I left it alone until last month. After jacking up the truck, seeing if wheels moved or were powered (they spun by hand but weren't powered) etc., & tracking down the vacuum lines, all seemed intact as did the various fuses. I took it to the shop since I'm not well-versed with an eletrical tester. Bad ADD motor up front. Reasonable parts cost and I dont begrudge the labor since I certainly couldn't have figured it out in a timely fashion. Glad I had it fixed- we had a slippery drive out to Kirkwood for a last powder day of the seaon! And I'll feel more comfortable on an upcoming Baja trip.

So I suspect it was a combination of two problems. Old & cracked vacuum hose to the transfer case and a failing ADD motor. To recap, if your 4wd light does not go on, BUT you can put the truck into 4wd low and engage the locker and the front wheels aren't powered while on jackstands, check the ADD motor. Clear as mud, yes?


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