Odd 4wd issue searched and still need help

Q

Quadsbc

New member
2000 limited auto

Ok having an issue with 4wd and 'awd' will not engage the t case or front diff. When operating the push button Vsv has vacuum and switches when 4wd button is pushed. But the t case shifts to neutral I can do this at a stand still or on the fly same happens and I have no drive. If I switch the vsv hoses the t case will still not engage. Both f/r driveshafts will lock just no drive. This happens in park with the truck off key on. I push the button, f/r driveshaft locks together and I can push the truck around in park.

Now if I shift to 4hi I'm still in 2wd front diff does not engage. But I still have rwd and the front and rear drive shafts are locked together. Same happens when I shift to 4Lo. Still 2wd and low range.

What would cause this? It seems like there is two issues. The hoses are still flexible and the truck looks new under the hood.

I've been using this as my troubleshoot process.
TheDurk said:
Well, that's the first thing to figure out. I'm not familiar with the multi-mode, but I think this should work:

First, verify front shaft turns by hand in 2wd. With key on, engine NOT running, engage 4HI. If shaft locks, T-case is good, ADD system is bad. If shaft still turns problem is in T-Case. (The ADD--Automatic Disconnecting Differential--runs on vacuum so it will not engage with engine not running, but the T-Case on the multimode is electric, so it should engage with just the key on.

If the ADD is the problem, here is how to troubleshoot (from an earlier post of mine):
Don't guess at it, troubleshoot! Start at the twin VSV's (Vacuum Switching Valves) on the driver fender wall. There are two long vacuum hoses that come up from the diff, one goes to each VSV. Check to see that one of the two hose nipples on the VSV’s has vacuum (engine running, 4WD NOT engaged). If no vacuum either side, check the check valve going to the intake manifold and look for loose hoses or a hole in the reservoir. If there is vacuum going to one hose, then put it in 4WD. See if the vacuum switches to the other hose. If it does, and no 4WD, problem is the diff actuator or the line to the diff. If it does not, then just switch the hoses and you should go into 4WD. This confirms diff is okay. (Mark the hoses first so you know which belongs where!)




OK, switch them back. Then use a test light to see if electrical signal from the TC also switches sides of the VSV. If it does not, problem is the TC, the switch on the TC, or the TC actuator, or its wiring back to the button (last two for non-J shift only). If it does, but the vacuum does not, the problem is the VSV itself.




I start troubleshooting at the VSV's because you can figure out where the trouble is without having to climb under the truck. [Does not apply to '01-'02]


If the multi-mode T-Case is the problem, somebody else needs to help. I don't do slushboxes.
Click to expand...
 
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Thanks for the info, I really hope it's not that but probably is. I couldn't guess the last time this was put in 4wd, probably many years.
 
I had a similar issue on my 99 limited ( multimode), I bought it that way- 4x4 in limbo . the t-case actuator should be the last thing you think of right now -start small pull the switch out of the front diff and use a ohm meter to check it . with the ball compressed it should read open ,and with it in the resting position it should be closed . if the signal is not steady replace it they are cheap . then check the switches on the t-case with the same process . there are 5 or 6 switches in total 3 or 4 are the same - a "backup lamp switch " for a 97 tacoma with a manual trans . autozone has them for $23 /dealer was over $100
my issue ended up being the one way vacuum "pod" right next to the oil cap on the motor someone knocked it loose and put it on backwards so no vacuum was getting to the vsv
hope this helps
 
Thanks [MENTION=85977]chrisb[/MENTION] I think I have two separate problems. I was trying to find wether the switch in the front diff is normally open or a normally closed switch. I'll check resistance hopefully tomorrow. I can hear the t case actuator working, just was unsure if the actuator was fully engaging, or if it even is responsible for connecting f/r driveshafts and t case to the tranny. When I push the button and try to drive I get a light grinding noise.
 
When was the last oil change on the t-case try some good oil it could be just hanging up old oil and not used much ? I couldn't remember on the open or closed for add switch are you getting a flashing 4wd light?
 
i would do fluids in the t-case and front diff
if you can change the switch in the front diff
Part Number: JA449 from autozone its a back up light switch for a 99 4runner with a 5 speed it's $21
since you will be down there already
change the fluid and drive it to work the new fluid around ,after a few days try the 4wd again
your saying while driving the multimode button will through the t-case in neutral?
 
Yes. It will go to neutral. While driving, in neutral or in park. And when I exit multimode it goes back into gear. This happens with the car off or running.
 
oh man that's rough i would start hunting for a good deal on a replacement t-case . i will keep chewing on it and see if i can think of anything .
it makes me think that if the light is solid on the dash that the computer thinks it's in 4wd , and is the mechanical part of the t-case just isn't completing the cycle to awd/4wd but thats just a assumption
can anyone help !!!!
 
a friend of mine who is a long time toyota tec here in tucson says when he gets the multi mode t-case with issues ( pretty often) he uses a air hammer and finds a part of the t-case that is solid and vibrates the t-case which jars the contacts in the actuator . he say it works on about 70% of the t-cases he says with them sitting for years and no activity they build up some sort of resistance /corrosion and it solves most of the problems
if anything it's another stone to through
 
chrisb said:
I had a similar issue on my 99 limited ( multimode), I bought it that way- 4x4 in limbo . the t-case actuator should be the last thing you think of right now -start small pull the switch out of the front diff and use a ohm meter to check it . with the ball compressed it should read open ,and with it in the resting position it should be closed . if the signal is not steady replace it they are cheap . then check the switches on the t-case with the same process . there are 5 or 6 switches in total 3 or 4 are the same - a "backup lamp switch " for a 97 tacoma with a manual trans . autozone has them for $23 /dealer was over $100
my issue ended up being the one way vacuum "pod" right next to the oil cap on the motor someone knocked it loose and put it on backwards so no vacuum was getting to the vsv
hope this helps
Click to expand...
Would you be able to confirm that with the switch in resting position in 2wd it is closed? I've tested the front diff (open) and two on the transmission blue drivers side (open) and white above blue( open). It seems odd that all would read open. I haven't pulled the switch, it's raining sideways and I got tired of being dripped on in the garage.
 
I just stopped checking after three switches. Either all the switches were good or bad. But it's unlikely all switches are bad
 
Why not run a manual t-case from a Tacoma?

People will say they're different lengths, blah blah blah, I'm in here to tell you that you CAN run a manual t-case with NO drive line modification.

Just zip-tie the wires for the CLD along the wiring harness and you're all set.

Run the front ADD to a switch, and you're golden.

Convert the front ADD to Full time "locked", as in 4WD, and manual hubs, and you're platinum.
 
I'll find out soon but I'd be happy if I shift into 4hi and had 4wd. I don't really plan on using the push button 'awd'. I'll be replacing the front diff switch which should let the front diff engage once shifted into 4hi.
 
Ok, replaced front diff switch and added new hoses. Front diff still does not engage. Checked diff switch when actuated. It is closed and opens when taken out of 4wd. Voltage is 10.3v battery is 12.6v. Diff fluid is clean from po. I can switch vacuum hoses and still nothing. Thinking it is the vacuum actuator is seized.

As for the center diff actuator, pulled the electrical connector off and tested resistance through pin 2 and 3, .9 ohms and both open to ground. I couldn't pull a voltage test on pin 2/3 incoming. I've jumped 12v from between 2/3 and the transfer case switches between 2wd and 4wd however it still does not engage the transmission in push button 4wd. Truck can be in park and if I hit the push button I can roll the truck anywhere I want. I can spin the driveshafts both will spin only rear tires move because the front diff still doesn't engage.

This is fustrating.
 
Doc2012 said:
Why not run a manual t-case from a Tacoma?

People will say they're different lengths, blah blah blah, I'm in here to tell you that you CAN run a manual t-case with NO drive line modification.

Just zip-tie the wires for the CLD along the wiring harness and you're all set.

Run the front ADD to a switch, and you're golden.

Convert the front ADD to Full time "locked", as in 4WD, and manual hubs, and you're platinum.
Click to expand...

Would you have any more info on this swap? Even if it's just the manual hubs and full time locked
 
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