HAVE A 1999 TRACKER. IT IS GETTING VACUUM TO THE ACTUATOR ALL THE WAY BACK TO THE FRONT DIFFERENTIAL. NO LEAKS IN ANY TUBES OR HOSES. THE FRONT DRIVE SHAFT SPINS BUT DOESN'T ENGAGE IN THE DIFFERENTIAL AND HENCE THE 4WD DOESN'T WORK. I THINK THE PROBLEM IS IN THE FRONT DIFFERENTIAL. IS IT POSSIBLE TO LACK VACUUM IN THE DIFFERENTIAL? WHAT IS THE LEAST EXPENSIVE FIX? THANKS IN ADVANCE FOR YOUR HELP

SOURCE: 89 jeep wrangler 4wd problem

The float in the tank is probably stuck or gummed up. Try a can of sea foam or Chem tool and checking for broken lead wires before removing the tank.

SOURCE: Bearing on 4WD front differntial drive shaft yoke

In short yes, the bearing is pressed on the pinion gear, the only way it will come out is to remove cover on housing and pull carrier with ring gear out, and also yoke that drive shaft bolts to, then pinion will come out, there is also a crush sleve that will have to be replaced when it goes back together it goes over the pinion gear, thats for backlash ajustment when you tighten the pinion back in the housing. if you plan on doing this yourself you will also need a dial indicater to set the backlash. If you want my advise take it to a shop to have it done, if you don't get it right it could end up costing you alot more than if you took it someware and had it done.

SOURCE: S-10 Blazer 4wd problem

www.amazon.com/Chiltons-Repair-Manual.../0801981425


Hope this helps you

SOURCE: output shaft separated from output tube 93 Jimmy

You need to disassemble the front diff as there is a clip that holds the shaft in the housing. You should just be able to remove the housing if it is the right side, whole diff for the left side.

SOURCE: 4wd wont work on 1999 chevy tracker but front drive shaft is turning?

The locking hub control system is not engaging properly. On the 99 Tracker this is a compressed air system that consists of an air pump (compressor), electrical wiring to power and control the air pump, and air hoses that lead to an actuator inside the front differential housing. If there is a leak in the system the PCM will run the air pump for 10 seconds and then shut off, and your propeller shaft can turn all day long, but the front axles will remain free floating. Turn on your key, not your engine, and engage four wheel high. Go listen near the passenger front bumper for the air compressor. If you hear it, then the compressor control and the compressor itself are likely fine. If it shuts off after 10 secs or so, and your 4WD light isn’t on, the PCM timed out the compressor out and shut the compressor off to protect it. You will have to find the leak and fix it. If you are lucky, it’s the air line leading to the front differential; and not the air line inside the differential housing, or the air bladder in the locking actuator, which also resides inside the font diff. If the compressor shuts off and the 4WD light is on (this means the PCM did not shut the air compressor off due to timeout, so the pressure switch read 5-7 psi and the pump shut itself off), you likely don’t have a leak, and something mechanical has the actuator hung up inside the front differential. Lastly if you don't hear the compressor run at all, you either have a faulty compressor, or some sort of wiring problem in that circuit.....it could be as simple as a blown fuse. Good luck.