Hello i am in need of some technicial assistance. For some strange reason my front differential does not want to engage. After attempting to go 4 wheeling last weekend i found out that the front tires are NOT being turned. I did some tests and found that the both vsv valves are functioning correctly and that the the vaccum lines are set up correctly also the transfer case works becouse i can feel the difference in the gearing when engaged. The vacuum actuator and switch tested perfect the actuator held a vacuum in both directions and the switch closed and opened when it was supposed to. So i still don't know what the problem is also does anyone know if if one of the leads on the transfer switch is supposed to show continuity to ground. OH the vehicle is a 1992 toyota 4 runner sr5 v6 5 speed stick with a 3.slow.

 

The transfer case switch does have a grounded lead, the black/white one. When you select 4 wheel drive that switch will ground the ADD relay, which will then switch power from the 2wd vsv to the 4wd vsv. This then sends vacuum to the engage side of the vacuum actuator which should move a sliding collar to connect the driver side shaft.
The only problems I've had with 4wd is vacuum lines getting damaged so I'm not sure what the problem could be in your case.
Maybe this will help
http://www.off-road.com/toyota/tech/add/

 

hey i thihk im having the same problem with my 94 4runner 3.0, dose the 4wd light turn on??, i have no clue what the problem is, when i put it in to 4wd the light will turn on for a second then turn off

 

If the light goes on, then the front axle is engaged - that light is in a circuit with a positive feedback sensor that really does tell you that the yoke really did move the gears.

So, if the light goes on, but there's no front end spin, then you're looking at something external to the diff. Likely culprit would be a CV joint.

 

Stevo solved this problem, send him a PM and ask. I think he said it was a vaccuum issue or something.

 

Im having a similar issue. When I tried to run my 4WD around my apartment complex, I felt no change after the lever was set to 4H and the light did not appear on my dash. I do not think it is a CV joint issue as I had both replaced a year ago and I did have engine work done were the shop removed my transmission, however, it was working before then. Any thoughts guys?