Bullwinkle94

I replaced a cracked vacuum line on the trans near the shifter but that didn't fix it.. I will replace the ones going down to the front end this weekend just to see what that does

fishy_mcfish

is your truck stuck in 4 wheel drive all the time? I am having, what seems to be the same exact issue with my 90 toy truck. I get vacuum at the brown vsv but nothing at the blue one! I also had one of the vacuum lines leading from the vsv down to the add actuator broken. replaced it and still nothing has changed. I am stumped as well. I was thinking about pull the ADD actuator off and checking the fork and stuff for damage.

Bullwinkle94

4wd will not engage,, haven't made time to replace the vacuum lines yet. Might do it today if it will ever stop raining..

CLUBFOOT

I have spent some time on the truck the last few days and my situation remains the same. I have made the following observations.

I have no "click" sound under the dash when key is on and I switch between 2HI and 4HI. This leads me to believe that the problem lies within the ADD relay rather than having 2 faulty switches on the transfer case (please correct me if I am wrong in thinking that there is a transfer case switch for both 4HI and 4LO).

Looking at my FSM, it is very difficult to determine the location of ADD relay. I have spent the last 2 evenings digging underneath the dash for it. I read on another forum that the ADD relay was labeled "fuel pump relay". I find this hard to believe. Can someone chime in here?

I noticed something else under the hood tonight. Looking at the vacuum hoses at the VSVs, there is a four way splitter. The splitter delivers vacuum from the source to both VSVs and one other hose that runs straight back under the washer fluid reservoir to a nipple on the fender. Next to this junction, there is another nipple that has no hose connected. It is just there. Anyone know what purpose these nipples on the fender well serve? Should both have hoses connected to them?

I am able to manually switch vacuum source straight to ADD and engage 4HI and 4LO, bypassing the VSVs so I know that the actuator is ok. I can feel that it engages but I still get no light on the dash.

Your help is greatly appreciated.

CLUBFOOT

JasonYota

iTrader: (1)

There is only one switch on the transfer case for the 4wd.

CLUBFOOT

I just read that the ADD relay has its ground completed by both a Transfer Indicator Switch and a Transfer Pressure Switch for V6 with Auto Transmission. I will look for these tomorrow.

http://www.off-road.com/trucks-4x4/t...tem-19259.html

CLUBFOOT

Made it under truck tonight and again tried to remove the switch on the passenger side of the T-Case. This time I believe I broke the switch by trying to turn it. It now is loose with a couple of wires still connected to the inside of the T-Case. I took the truck out for a drive and got a flashing light on the dash that said "O/D OFF". I assume this is a repercussion of breaking the switch and am now about to drown my sorrows in beer and fried chicken. If anyone has any recommendations, please advise.

JasonYota

iTrader: (1)

Don't go work on it after the beverages and chicken. That's the only recommendation I have at the moment

CLUBFOOT

Took the truck to the local shop. They said to remove and replace the sensor will require dropping the transmission - around a 9.5 hour job.

There is about a 1.5 inch piece of the sensor floating around in the tail shaft section of the tranny. Can anyone verify that this piece of plastic has to come out? I have the replacement on the way and would love to hear that there is no significant risk in leaving that old one in there.

This thread started as a 4 wheel drive question and has changed significantly since then. I have learned a lot and will continue to learn more with all of your help. Thanks,

CLUBFOOT

CLUBFOOT

After fishing out the broken sensor and replacing, it has been a productive summer. I have done just about everything I have wanted to get done on this truck before paint and body work but have still yet to get to the bottom of my 4wd issue.

My focus is still on the ADD relay. Does anyone with the 3.4 V6 Auto Trans know where the ADD relay is located? The only relay I have found near where the FSM shows it is printed "Fuel Pump Relay" and is under the instrument panel.

Thanks,

CLUBFOOT

CLUBFOOT

I read today that the Toyota ADD relay is often labeled Fuel Pump Relay. I pulled the "Fuel Pump Relay" from under the steering column and verified per the tests in the FSM that it is the correct part. That felt good.

I was hoping that it would fail the tests but it passed per the FSM. Now I am thinking possibly an open somewhere in the wiring. If anyone has any insight from here please share.

Thanks,

CLUBFOOT

CLUBFOOT

Upward.

Timyota100

Not to Hi-jack this thread, but I have searched everywhere on a ton of forums and haven't found anybody that is describing the issue that I'm having. The issue: Just bought a 1997 T100 4x4, and the 4x4 doesn't engage. What happens when I shift into 4hi or 4lo: Light on the dashboard immediately lights up, I hear a clicking in the dash from the relay, and I hear a sort of wirring/rubbing sound coming from the tcase/diff area. I have checked all the vacuum lines, solenoids, etc. Vacuum is applied to the right lines at the right time, so I have ruled out the solenoids and possible vacuum issues.
With the front wheels jacked up in 2wd both wheels spin freely (not moving the others, like a 2wd truck.) When I shift into 4wd the wheels slightly turn each other but not locked in like they should be. I thought the ADD in these trucks meant the front axle was always locked, even in 2wd. But obviously I'm misinformed. Plz halp.