4x4 will not work!!!

[pmhvps]

That title thread seems to get a response.
"If the front wheels do not spin in opposite directions, there is a problem with the front axle. This could be due to a mechanical problem with the diff, or a failure of the center axle disconnect to engage the passenger side axle shaft. Start a new thread with the results of your checks, and we'll go from there."

On the '95-'96 Did steps 1-4. All checked out but step 4. Only one wheel spins. Did both sides. Now what?

Mike.

I guess I need this info, "Troubleshooting the CAD on a 95-96 is a bit more involved than I want to get into here, and the problems can vary widely"

 

[96eb96]

That title thread seems to get a response.
"If the front wheels do not spin in opposite directions, there is a problem with the front axle. This could be due to a mechanical problem with the diff, or a failure of the center axle disconnect to engage the passenger side axle shaft. Start a new thread with the results of your checks, and we'll go from there."

On the '95-'96 Did steps 1-4. All checked out but step 4. Only one wheel spins. Did both sides. Now what?

Mike.

I guess I need this info, "Troubleshooting the CAD on a 95-96 is a bit more involved than I want to get into here, and the problems can vary widely"

are you in 2wd or 4 auto when you do the tests?

 

[pmhvps]

are you in 2wd or 4 auto when you do the tests?

I'm in 4X4 LOW light on. Engine running in Park. Wheels off the ground, front drive shaft won't turn, wheel turns by hand, but opposite wheel doesn't.

Mike.

 

[96eb96]

PINPOINT TEST A: DISCONNECT AXLE/SHIFT MOTOR DIAGNOSIS (4WD)

A1 INVESTIGATE WHETHER FRONT AXLE CENTER DISCONNECT IS ENGAGING
Start engine and depress brake pedal. Place transfer case in 4H position.
Raise vehicle so all four wheels are free to rotate.
Place transmission lever in drive (automatic) or 1st gear (manual) to confirm transfer case engagement in 4H. Let wheels rotate slowly.
Do both front wheels rotate?
Yes No
CHECK wiring from GEM controller to vacuum disconnect switch on axle. GO to A3 . GO to A2 .

A2 CHECK FOR FRONT DRIVESHAFT ROTATION
Check transfer case. Repair as necessary.
Does front driveshaft rotate?
Yes No
GO to A4 . REPEAT A2 .

A3 CHECK 4WD INDICATOR LIGHT OPERATIONAL
Check 4WD indicator light is operational.
Is 4WD indicator light working?
Yes No
Repair is complete. CLEAR DTC codes. INSPECT 4WD indicator switch wiring and lamp for damage. REPAIR as necessary. PERFORM A3 again. If results are satisfactory, repair is complete.

A4 CHECK VACUUM SHIFT SYSTEM FOR PROPER OPERATION
Place transmission lever in neutral position.
Remove vacuum hoses from axle shift motor ports.
Start engine. Test for vacuum at hose removed from outboard port on shift motor.
Is vacuum between 33.6-67.3 kPa (10-20 in-Hg)?
Yes No
GO to A5 . GO to A9 .

A5 PERFORM VACUUM TEST
Stop engine.
Connect vacuum pump to the outboard shift motor port and apply 50.5 kPa (15 in-Hg) vacuum and rotate right wheel.
Is front axle engaged?
Yes No
GO to A6 . GO to A7 .

A6 PERFORM INSPECTION
Inspect vacuum hoses for leaks, kinks, etc. Repeat as necessary.
Does system perform as required?
Yes No
Repair is complete. REPEAT Steps A5 and A6 .

A7 TEST FORK MOVEMENT
Remove shift motor housing cover. Connect vacuum pump to shift motor port.
Does fork move in and out freely?
Yes No
REPEAT Step A5 . GO to A8 .

A8 REPAIR OR REPLACE COMPONENTS
Remove shift motor housing cover and inspect shift fork, collar and axle shafts. Repair or replace as necessary.
Does system perform as required?
Yes No
Repair is complete. REPEAT procedure from Step A1 .

A9 PERFORM INSPECTION ON VACUUM COMPONENTS
Inspect intake manifold vacuum supply hose connection, transfer case vacuum switch connection, vacuum reservoir and shift system vacuum hoses for proper connection, restriction, leaks and damage. Repair or replace as necessary.
Is there proper vacuum?
Yes No
Repair is complete. CHECK transfer case vacuum switch. REPLACE or REPAIR if switch plunger is difficult to move or binds. REPEAT A9 .

PINPOINT TEST B: DISCONNECT AXLE/SHIFT MOTOR DIAGNOSIS (2WD)

B1 INVESTIGATE WHETHER FRONT AXLE CENTER DISCONNECT IS DISENGAGING
Raise vehicle so all four wheels are free to rotate.
Inspect indicator switch and wiring on shift motor housing for damage and short circuit. Repair as necessary.
Is 4WD indication system functioning properly?
Yes No
Repair is complete. GO to B2 .

B2 CHECK FOR WHEEL ROTATION
Start engine and depress brake pedal. Place transfer case selector in 2H position and transmission in drive (automatic) or first gear (manual). Ease off from brake and let wheels rotate slowly.
Does front right wheel rotate?
Yes No
GO to B3 . Repair is complete.

B3 CHECK VACUUM SHIFT SYSTEM FOR PROPER OPERATION
If 4WD indicator light remains on, place transmission in neutral and disconnect the shift motor vacuum hoses.
Test for vacuum in vacuum hose that connects to inboard shift motor port.
Is vacuum between 33.6-67.3 kPa (10-20 in-Hg)?
Yes No
GO to B4 . GO to B6 .

B4 PERFORM VACUUM TEST
Stop engine.
Connect a vacuum pump to the inboard shift motor port. Apply 50.5 kPa (15 in-Hg) of vacuum and rotate right wheel.
Does front axle disengage?
Yes No
GO to B5 . GO to B7 .

B5 INSPECT VACUUM SHIFT SYSTEM
Inspect vacuum hoses for air leaks, kinks, etc. Repair as necessary.
Does system operate properly?
Yes No
Repair is complete. REPEAT entire procedure.

B6 PERFORM INSPECTION ON VACUUM SYSTEMS
Inspect intake manifold vacuum supply hose connection, transfer case vacuum switch connection, vacuum reservoir and shift system vacuum hoses for proper connection, restriction, air leaks and damaged. Repair or replace as necessary.
Is vacuum within specification?
Yes No
Repair is complete. REPEAT procedures starting from B3 .

B7 PERFORM VACUUM TEST ON ARMATURE
Remove shift motor housing cover. Connect vacuum pump to shift motor port. Replace shift motor if armature does not move in and out freely.
Does front axle disengage?
Yes No
Repair is complete. REMOVE shift motor housing cover. INSPECT shift fork, collar and axle shafts. REPAIR or REPLACE as necessary. REPEAT Step B7 .

 

[pmhvps]

Thanks so much. This should help alot. To think, in the old days we had to pull levers and get out of the vehicle to turn knobs to lock hubs if we wanted 4X4. Now, it's so easy....just turn a switch....

Mike.

 

[96eb96]

Thanks so much. This should help alot. To think, in the old days we had to pull levers and get out of the vehicle to turn knobs to lock hubs if we wanted 4X4. Now, it's so easy....just turn a switch....

Mike.

No problem.
Yeah, its a complicated system with the GEM computer commanding a vacuum relay to push a shift motor and slide some sleeve on the drive shaft. Lots of fun to troubleshoot.

 

[Diff Whack Daddy]

Once you read the tests, it seems pretty easy. I will be doing this in the near future as I have fixed the indicator lights with the battery disconnect trick, but the CAD doesn't seem to be working based on the fact the wheels turn independetly when in 4low. I knew it wouldn't be that easy.

 

[pmhvps]

Thanks so much. This should help alot. To think, in the old days we had to pull levers and get out of the vehicle to turn knobs to lock hubs if we wanted 4X4. Now, it's so easy....just turn a switch....

Mike.

It was going to cost me about $1500 to fix it. I sold it and bought a nice '89 Bronco II with manual transfer, manual hubs and auto trans. It is one rare Bronc. Not too many made with that combo.

Mike.