4WD problems with a 95'

[Red3.slow]

As a Noob I apologise If I've missed any additional threads on this subject, but here's my problem.

I recently purchased a 95' 4runner with a 5spd and I cannot seem to get the 4wd to engage. I have been told, by a friend, that he's seen my front wheels spin when i was going up a hill at one point. But the 4 wheel drive light on the dash has never come on and I do not thing the diff is engaging. I do know how ever the transfer case is locking the front drive shaft. I just got back from trying to swap around the vacume hoses on the diff and still nothing has seemed to change. thanks for the help.

 

[regularguy412]

If you have an open diff on the front (or rear), only one wheel on each axel will get power applied to it at a time. Unfortunately with an open diff, the one that gets the power is the one with the LEAST amount of traction.

Get your buddy to watch both front wheels closely. Lock in to 4H and do a little snap acceleration in some loose gravel. See if you can get a front tire to spin.

If it does,,maybe the bulb on the dash is burned out.

Mike in AR

 

[Red3.slow]

And what if one or the other doesn't.

Thanks for the help

 

[regularguy412]

And what if one or the other doesn't.

Thanks for the help

If neither front wheel spins and the back one does when you're locked into 4WD, you probably have a vacuum leak. I'm assuming you have ADD ( Automatic Disconnecting Differential hubs on the front ). The ADD is actuated by vacuum lines. The lines come off of ports located in the engine compartment and attach near the middle of the front diff. The vacuum also serves to throw a switch that makes the light on the dash illuminate.

Check for loose or cracked vacuum lines. There are two of them.

Mike in AR

 

[captwalker87]

The vacuum actuated sleeve in the front diff is known to go out. Your vacuum lines control this sleeve and if it does not engage then neither wheel will spin, because of your open diff explained above. Check to see if the sleeve locks by flipping the vacuum lines while the truck is on in 2WD. If you hear a knock from the front diff, its working.

 

[Red3.slow]

Could manual locking hubs just simplify this?

EDIT: It snowed a little bit today and I can say with I'm about 95% positive my 4wd is functing now. Thanks for the advice guys.

 

[Red3.slow]

One more question dealing with this. The wires that come off the front of the diff, those are for the dash light correct? Is their an in line fuse or something that could be keeping the dash light from coming on? or could the front diff only be partially engaged.

Sorry for all the noob questions

 

[regularguy412]

One more question dealing with this. The wires that come off the front of the diff, those are for the dash light correct? Is their an in line fuse or something that could be keeping the dash light from coming on? or could the front diff only be partially engaged.

Sorry for all the noob questions

Someone correct me if I'm wrong, but I think the dash 4WD light is actuated by the vacuum valve on the passenger side inner fender. Seems like I read somewhere that when the valve switches( to put vacuum on the system and engage the front drive shaft) it makes electrical contact and sends power to the dash light.

Also, I believe the ADD hubs are always 'locked'. That is, the CV joints turn all the time, even in 2WD. But they don't 'pull' until the ADD sleeve engages when vacuum is applied. The vacuum pushes a sliding sleeve in the front diff assembly to get torque from the driveline applied to the front axel(s).

Mike in AR

 

[Red3.slow]

OK I think I'm starting to see how they put this together. One thing I'm still confused on is what do those two wires do?

I can take and post a picture if that will help.

 

[regularguy412]

OK I think I'm starting to see how they put this together. One thing I'm still confused on is what do those two wires do?

I can take and post a picture if that will help.

Pix are always good !

Mike in AR

 

[Red3.slow]

I hear ya! Give me a bit and i'll have them

well that'll have to wait. Its started snowing and my cam's batteries are dead.

 

[regularguy412]

snowing again here now, too. No prob.

Mike in AR

 

[captwalker87]

The two wires that come out of your diff are part of the 4WD indicator system. The wires send a signal when the sleeve is engaged. Also, your transfer case has a 4WD indicator switch just like the one on your front diff. The 4WD vacuum swithces on the passenger fenderwell also have a 4WD indicator signal. All of these signals must be there for the 4WD indicator light to come on. Its a simple 4WD diagnostic system. Usually, the 4WD indicator light would flash if one of these signals were not coming in. Its possible your light went out.

 

[Red3.slow]

I talked to the previous owner today. He told me a few months before I bought the car he was having some work done and they told him the 4wd wasn't working. After 3 hours they figured out it was simply the dash light. So that helps. I'm still not going to feel safe enough to really hit the trails again till I have someone tell me for sure it is working.