Valvoman

Looking to this board for help.

1993 extended cab pickup, 3.0, 5 speed, SR5 w/ 163,000 miles. Everything is all original, meaning no electrical or vaccum hacks. And, this thing has probably never been off road, so the 4wd was most likely never exercised regularly.

-->When I put it in 4H, front driveshaft does not turn. No dash light. No 4 wd.

-->When I put it in 4L, front driveshaft does not turn, No dash light, No 4wd.

-->When I return it to 2H, front driveshaft turns.

-->VSV has vaccum on the radiator side at all times. There is no vacuum on the cab side.

-->Swapped VSV lines to front diff with no change in results.

Any thoughts? Should I tap on the diff actuator to maybe free it? Could that be it?

Thank you in advance.

wyoming9

iTrader: (1)

Good bet that from being unused it is stuck or rusted.

I don`t know if tapping will help you might need to pull things apart.

Who knows you might get lucky!!

RJR

You can pull off the actuator mechanism from the diff pretty easily to see what is stuck inside, if that's the case. First, though, do the following procedure.

- Put vehicle in 2wd, block the rear wheels, and set the e-brake.
- Jack up both front wheels and safely support them on jack stands.
- Apply at least 6 inches of vacuum to one side of the actuator and rotate one of the front wheels. If the actuator is engaged, the other front wheel should rotate in the other direction and/or the front drive shaft should turn. If the actuator is disengaged, the wheels should free-wheel independently of each other.
- Now apply that vacuum to the other side. You should get the opposite behavior.

If you don't get different behavior depending on which side of the actuator gets the vacuum, you know for sure the actuator is stuck or defective and you need to tear it apart. It could either be stuck, as Wyoming suggested, or it could be a torn diaphragm in the actuator rendering it inoperative. Once you have the actuator off, you can apply vacuum to each port and watch if it moves or not. You can also manually slide the locking collar back and forth to see if it moves freely. Just be sure when you reassemble to get the actuator fork back in the slot in the locking collar. It's pretty obvious how it goes back together.

Valvoman

Thanks fellas.

@Wyoming9-I hope it's not rusted...been in Phoenix it's whole life.

@RJR-I will try that.