When the transfer is shifted from 2WD to 4WD and riving is begun, rotation of the driveshaft is transmitted from the drive gear to the slide gear to the cam to retainer (A) to brake (A). When this happens, brake (A) is pressed against brake (B) by the function of the cam of retainer (A), and friction force is generated.
Because brake (B) is secured to the knuckle, retainer (A) ceases to rotate, and therefore, the cam, while compressing the return spring, rises out of the cam groove of the retainer (A) and compresses the shift spring. The slide gear is pushed by the shift spring, and then engages with the gear of the housing when the two are in phase and enters the locked state.
The cam turns until the lug of the drive gear contacts the lug of the brake (A). Because of this contact, brake (A) is turned by the drive gear, and therefore, there is also no longer any force of retainer (A) with a tendency to turn brake (A). As a result, there is also no longer any force which presses brake (A) against brake (B) and the drive gear causes brake (A) to turn lightly (there is no friction force).
Fig. 1: Internal workings of the automatic-change 4WD free-wheeling hub assembly-all 1983-95 Pick-ups (4WD) and some 1983-95 Monteros
Because the cam remains meshed, it turns until it contacts the lug of retainer (A), and is locked.
When the transfer is shifted from 4WD to 2WD and the vehicle is driven in reverse, rotation of the gear of the body is transmitted from the slide gear to the cam to the retainer (A) to the brake (A), but retainer (A) ceases to turn, just as when the shift is made from the free state to the locked state. The cam, therefore, turns as far as the cam groove of retainer (A) and is pushed into the cam groove by the return spring.
The slide gear moves with the cam, disengages from the gear of the body, and enters a free state.
DISASSEMBLY & ASSEMBLY
See Figures 2, 3, 4 and 5
Place the free-wheeling hub in the free condition. To do this, shift the transfer shift lever to the 2H position, then move the vehicle 4-7 ft. (1-2 m) backwards.
Remove the front wheels of the vehicle, and support the raised front end of the vehicle with jackstands.
Remove the automatic free-wheeling hub cover. When the cover cannot be loosened by hand, use an oil filter wrench with a protective cloth in between not to damage the cover. Remove the O-ring from the underside of the hub cover. A new O-ring will be needed upon reassembly.
Using a pair of snapring pliers, remove the snapring from the driveshaft.
Slide the washer (shim) off of the driveshaft.
Unscrew the 6 retaining bolts from the automatic free-wheeling hub assembly and slide the assembly off of the driveshaft.
Remove the rear housing C-clip, which is easily removed by pushing the brake (B) in and using a small prytool to pry it out.
Go to link below to see enlarged illustration
Fig. 2: Axle hub and free-wheeling hub assemblies' removal and installation-automatic-change 4WD systems
Fig. 3: Automatic free-wheeling hub assembly disassembly and assembly components
Remove brake (B), brake (A) and the brake spring from the housing.
Use a small prytool to remove the housing snapring.
Using the special tool MB990811-01, lightly push (with a press) the drive gear in and remove the retainer (B) C-ring. Since the return spring relaxes approximately 1.5 in. (40mm) the stroke of the press should be set to more than 1.5 in. (40mm).
<Use a protective cover so as not damage the cover attaching surface of the housing before setting it on the press table. Make sure that the pressing force does not exceed 44.1 lbs. (200 N)
CAUTION When the pressure of the press is removed, make sure that the retainer (A) is not caught by retainer (B).
Slowly reduce the pressure of the press until the return spring relaxes fully. Remove the drive gear assembly, the slide gear assembly and the return spring.
Remove the retainer (B) and the retainer bearing.
Remove the drive gear snapring from the drive gear assembly. Separate the retainer (A) and the drive gear.
When the drive gear snapring is removed, be sure to replace it with a new one.
To remove the slide gear C-ring in the slide gear assembly, push the cam in and remove the slide gear C-ring with the spring compressed. Remove the cam, spring holder, shift spring and the slide gear from the slide gear assembly.
Fig. 4: When assembling the free-wheeling hub assembly onto the spindle, line the key and the key slot up-automatic free-wheeling 4WD systems
Fig. 5: Use a spring scale to measure the turning resistance both before and after the installation of the free-wheeling hub assembly-automatic free-wheeling 4WD systems
CAUTION Make sure that there is no excess sealant on the hub outside surface.
Assemble the slide gear, the shift spring, the spring holder and the cam to make the slide gear assembly. Install a new C-ring to the slide gear assembly.
Assemble the drive gear and the retainer (A) to form the drive gear assembly. Install a new drive gear snapring to the drive gear assembly.
Grease the following components with multipurpose grease SAE J310, NLGI No. 2:
Retainer (B)-pack the grooves of the retainer (B) with grease.
Brake (B)-pack the grooves of brake (B) with grease.
Install the components to the hub housing in the following order: retainer bearing, retainer (B), return spring, slide gear assembly, drive gear assembly, new retainer (B) C-ring, new housing snapring, brake spring, brake (A), brake (B), new housing C-ring. When installing the return spring, install it with the smaller coil diameter side toward the cam.
Using a spring scale, measure the front hub turning resistance without the free-wheeling hub housing installed yet. Note the amount of force needed to turn the hub assembly on the vehicle.
Apply a coating of 3M® ART Part No. 8661, or No. 8663, or the equivalent sealant, equally all around and without missing any spots, to the free-wheeling hub body assembly and the front hub contact surfaces.
Align the key of the brake (B) and the keyway of the knuckle spindle, then loosely install the automatic free-wheeling hub assembly to the spindle.
Check that the hub proper and the automatic free-wheeling hub assembly are brought into intimate contact when the assembly is forced lightly against the hub proper. If not, turn the hub until intimate contact is achieved.
Tighten the free-wheeling hub mounting bolts to 36-43 ft. lbs. (50-60 Nm). Use the spring scale to measure the front hub turning resistance again. Subtract the value measured from before from that now measured to find the turning resistance of the free-wheeling hub. The limit of resistance is 8.7 inch lbs. (1 Nm) or 3.1 lbs. (14 N) on the spring scale. If the free-wheeling hub turning resistance exceeds the limit, disassemble and reassemble the free-wheeling hub again.
Install the shim and the snapring to the driveshaft end. Screw the cover onto the hub assembly to 13-25 ft. lbs. (18-35 Nm).
Install the wheels to the vehicle. Lower the vehicle to the ground, then finish tightening the wheel lug nuts.