4wd engage by itself

1

1995runner

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My buddy has a 95 4runner, its Damn near mint condition. He has had it since it rolled off the dealers lot. It's amazingly clean, and maintence done by dealer. Right now however they are stumped. They want him to replace what seems like way to much, for a hopefully simple issue, that they can't figure out...

The 4wd is engaging by itself... Sometimes rides fine.. sometimes stuck in 4wd. The light was coming on, but now does not anymore. The truck is a 5speed manual, with a manual 4x4 shifter on the floor. I'm not familiar enough with these so I'm turning to you guys.

Any and all knowledge and ideas are very much appreciated.
 
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KidVermicious said:
More details needed. My first question would be if it was really going into 4wd, or if it only thought it was.
Click to expand...

It is, by itself, going into four wheel drive.. while driving. You can feel it engage, and slow down quicker when let off gas. Burning more fuel as well, and feel it when turning. The light was coming on, but it does not anymore.

I've questioned him over and over, and finely he brought to work for me to test drive. 4x4 manual gear selector in neutral, and she is def in 4wd...
 
Very odd. The next thing I'd do then is put it on 4 jackstands while the trouble is apparent and verify that there really is power to the front driveshaft - that'd point to the transfer case or shift linkage shoving the truck into 4wd spontaneously. If the front DS isn't powered, what you've probably got is something funky in the vacuum system or the actuator on the front diff that is actuating the slide collar and in effect locking your CVs together - that shouldn't feel like being in 4wd, but I can't imagine the transfer case just deciding to be in 4wd on it's own either.

Good luck!
 
I just put it in 4wd, and she drives much better.. so it leads me to believe its not fully engaging 4wd.. but its trying to.. I'm also getting a noise, not so much a grind as it is a wine, when I took out of 4wd and put back into neutral... When in neutral it feels like 4wd but not as good as it was when actually in 4wd.. hopefully that's not too confusing lol...

Actuator locking the cvs sounds about right... Where can I check the vacume hoses for the 4wd and how do I check or can I check the Actuator??

Thanks!
 
Actuator is on the front shaft. Disconnect and clamp the vacuum lines and see if that makes it "feel" right when it is in 2H. I agree though that I would throw it on jack stands first to see if the drive shaft is actually engaging. If the shaft is not engaging see if you can manually spin one front tire and watch to see if the other spins. This would tell you that the actuator is indeed engaging.

Also take a look towards the bottom of this tread http://www.toyota-4runner.org/classic-t4rs/117840-95-4runner-help-oil-leak-add-wiring.html. Fourwd1 put some really valuable ADD wiring info in there regarding the relays and actuator. Best bet for all this trouble shooting is going to be on jack stands though.
 
helo-mech said:
Actuator is on the front shaft. Disconnect and clamp the vacuum lines and see if that makes it "feel" right when it is in 2H. I agree though that I would throw it on jack stands first to see if the drive shaft is actually engaging. If the shaft is not engaging see if you can manually spin one front tire and watch to see if the other spins. This would tell you that the actuator is indeed engaging.

Also take a look towards the bottom of this tread http://www.toyota-4runner.org/classic-t4rs/117840-95-4runner-help-oil-leak-add-wiring.html. Fourwd1 put some really valuable ADD wiring info in there regarding the relays and actuator. Best bet for all this trouble shooting is going to be on jack stands though.
Click to expand...

Thanks, will do Saturday.. what is ADD?
 
I would start with the vacuum lines first. That was the problem with mine. The PO for whatever reason - had disconnected the two vacuum lines.

Reconnected them - and haven't had a problem since.

:bigok:
 
combatmedic said:
I believe, I may be wrong, is Auto Disconnect Differential.
Click to expand...

You would be correct. Toyota introduced it on trucks in 89 and 4Runners in 1990. It eliminates auto or manual hubs to lock the front axle. It connects 2 parts of the drivers side inner axle shaft. The actuator is mounted on the front axle housing right beside the diff.
 
Non ADD front axle top
ADD axle section bottom

IFS_diff2.jpg
 
The light not coming on anymore is probably the wire right behind the transfer case. It comes off the top of the tranny. The 2 wires, from what I've seen, pull out of the connector and thus no light. When you get under there look for a connector with a figure 8 at the end of the plug. There should also be 2 wires that look like needles dangling from the top of the tranny.
 
2009 engaging 4wd by itself

I have a 2009 SR5 4 Runner I purchased in July 2017. Since week one, I have been experiencing issues with the 4 wheel drive system. On 10 or so occasions now, when I come out to start my vehicle and pull away, the 4 wheel drive system is trying to engage itself. The 4 wheel drive light and center diff lock light blink while the vehicle is either trying to go into or already is in 4 wheel drive. Been to the dealership more than once and diagnostic tests showed nothing; couldn't mimic what I was experiencing. I have videos of this happening repeatedly. Please let me know your thoughts.
 
Sorry, but my first thought is that you need to be in a different area of the forums. This is the Classic section with first and second gen's, up to 1995. You're a bit newer than that, and you're not going to get answers around here very easily.
 
Agreed. Outside of the ADD system, there is nothing that can change when your tcase is in 2wd. Maybe you are feeling the engagement and disengagement of the outer shafts from a vacuum issue.

Let me tell you, if I had a 2nd gen I would rip that system out so fast and pop on manual hubs. What a headache.
 
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