Any suggestions on a 93' 4 runner that will not engage 4 wheel drive. The 4 wheel manual shifter works fine, and the linkage underneath looks fine; however, the indicator does not light up - and it definately only has rear wheel drive.

Thanks!

The front differential is vacuum controlled the light ONLY comes once the differential is fully engaged the switch is actually down on the diff. this diaphram is controlled by one of the VSVs up on the passenger inner fender in the engine compartment.
Check your voltages at the VSV and all vacuum lines from there down to the diff.
Ohm out VSV or just check the function by puttin a double lip locker on the hose and blow while applying voltage to the VSV, should change.

Might just be that your differential lube needs changing. Try new 75W90 gear oil and see if that helps. The vacuum-actuator for the front differential can stick if the lube is somewhat old.

What they said as well as check fuses and check the 4X4 switch(s) itself...not sure on this setup yet but many either have linkage(like ours) or micro switches even to let computer/tranny what phase it is in when in 4WD or 2WD.Might also check wiring to make sure it is all plugged in and pull connections apart and look for corrosion and/or water(don't forget to give transfer case a good going over for this as well as VSS's)......goodluck and let us know what you findout.