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Chuck
Chuck, ASE Certified Technician
Category: Ford
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Experience:  33 Years Experience,Ford Senior Master,ASE Master,L1 Advanced Engine Performance
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2000 ford ranger: Why doesnt the vacuum locking hubs engage?

Resolved Question:

2000 ford ranger: Why doesn't the vacuum locking hubs engage?
Submitted: 4 years ago.
Category: Ford
Expert:  Chuck replied 4 years ago.

This is a description of how the system works:

 

The four wheel drive system is an electronic shift 4X4 system that allows the operator to choose between three different modes. The operator can switch 4X4 HIGH modes at any speed. To engage or disengage 4X4 LOW the vehicle speed must be less than 5 kph (3 mph), the brake depressed, and the transmission must be in NEUTRAL.

The shift motor sense plate, an integral part of the electronic shift motor, informs the generic electronic module (GEM) of the transfer case shift motor and contact plates A, B, C and D position.

The digital transmission range (TR) sensor is located on the LH side of the transmission, and informs the GEM when the transmission is in the NEUTRAL position.

The electronic shift motor is mounted externally at the rear of the transfer case. It drives a rotary cam which moves the mode fork and range fork within the transfer case between the 4X4 HIGH, 4X4 LOW and 2WD range positions.

When the GEM verifies the completion of the transfer case shift from 2WD to 4X4 HIGH (reading the contact plate positions), the GEM will then energize both pulse vacuum hublock (PVH) solenoids (supplying ground for 45 seconds). The PVH solenoid will allow a HIGH flow of intake manifold vacuum to the "wheel end hublocks", engaging the wheel end hubs to the front differential and transfer case to achieve four wheel drive.

When the GEM verifies the completion of the transfer case shift from 4X4 HIGH to 2WD (reading the contact plate positions), the GEM will then energize only one (low vacuum solenoid) of the PVH solenoids (supplying a ground for 10 seconds). The PVH solenoid will allow a "LOW" flow of intake manifold vacuum to the wheel end vacuum hublocks, disengaging the wheel end hubs from the front differential and transfer case to achieve two wheel drive.

 

You will first need to check fuse 6(15amp) in the under dash fuse panel. This supplies power to the PVH solenoid. If this is ok then you will need to access the solenoid.

Here is a pic of its location,I have circled it in the bottom left corner.

 

graphic

 

 

Make sure you have power to it and see if you can feel it click when activated.

You can also check for vacuum to it and thru it with a vacuum gage. If all of this checks good then you will have to check for a leak at the hubs with a vacuum pump.

 

 

Customer: replied 4 years ago.
I had already checked the fuse...will check the PVH solenoid next.
Expert:  Chuck replied 4 years ago.
Sounds good.
Customer: replied 4 years ago.
I have discovered that the right hub has vacuum, but the left one doesn't. Just recently replaced the left hub bearing assy...could it be possible that I have a faulty hub assembly?
Expert:  Chuck replied 4 years ago.

When you say it does not have vacuum does it have vacuum to the hub?

 

You have a vacuum valve hub lock behind the inner fender well

 

Remove the screws. Deflect the inner fender to gain access to the vacuum valve

 

graphic

 

Here is the vacuum valve hub lock

 

graphic

 

 

When you replaced the hub bearing you didn't maybe crack the hub lock? You have to be careful when removing it, Did you replace the orings?

 

graphic

This is the hub lock

 

 

graphic

 

Special tool to remove the hub lock

 

graphic

 

Outer oring

 

graphic

 

Inner oring

 

 

 

Chuck, ASE Certified Technician
Category: Ford
Satisfied Customers: 2100
Experience: 33 Years Experience,Ford Senior Master,ASE Master,L1 Advanced Engine Performance
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