yo
WELCOME!
Have the manual locking hubs been inspected?
The issue seems to center around one locking hub stuck in an internally locked condition.
Operational Test in a 96 - same for your year; "...Manual locking hubs are simple to diagnose. Place the transfer case in 2-wheel drive and raise the front wheels off the ground. When in the unlocked position, the wheels should be able to turn freely. Then lock each of the front hubs and rotate the front wheels. The additional load of the drivetrain components should be felt once the hub has been engaged. In addition, the axle and front driveshaft should be moving along with the wheel. Disengage the hubs and repeat the procedure to check that the hubs have smoothly disengaged..." from 1996 F-150, F-250, F-350, and Bronco Workshop Manual
Operational Test; "... (engine off, hubs disengaged), crawl under the truck with the transfer case in 2HI, you should be able to grab the front drive shaft and turn it by hand. Also with the hubs disengaged you should see the front axles turning freely. Now engage the hubs and you should not be able to turn the drive shaft by hand. Jack the front wheels off the ground with the hubs engaged, turn the drive shaft by hand, the wheels should turn. The 4x4 light should not be on in 2HI, when in 4LOW you may have a low range light on, (not all trucks have that light) at least mine doesn't..."
Source: by Seabronc (Rosie, Fred W) at Ford Bronco Zone Forums
Operational Test; "The t-case disconnects the front driveshaft from the transmission, and the hubs disconnect the axleshafts from the wheels. The driveshaft is ALWAYS connected to the diff & axleshafts. Depending on how tight your diff is, both axleshafts MAY turn when you turn the d'shaft while BOTH hubs are unlocked, but at least one of them has to no matter what. If the d-shaft won't turn with both front wheels off the ground (or the hub locks removed), then the t-case is still in 4.
If either axleshaft won't turn with its hub UNlocked AND the t-case in 2 or N, then that hub is stuck locked. I suspect you'll find some carmelized grease, and some surface rust on the lock rings, and probably a spring or 2 heavily rusted, to the point that they're ruined. But that's just a guess. Take both hub locks OUT of the hubs, and then roll the truck a little. You don't need to remove the tires, or even jack the front end up since the locks don't bear ANY weight. If the d'shaft still turns, the problem is in your t-case..."
==================
Here is other stuff; most of which was suggested by BULLY BOB;
I'll leave it here for other tests and for posterity
This is by Ford in
Noise, Vibration, Harshness, Ride, Squeak & Rattles TSB 99-11-1 for 95-97 F 250, F 350, SD; 95-99 Econoline, Explorer, F 150, F 250, Ranger, Villager, Windstar and Many Others, Except that Ford Left Out Our Bronco
There is no info on the issue while Bronco is in 2WD & the issue disappears when in 4x4; except for the reverse;
Transfer case vibration—vibration felt with vehicle in 4WD
Transfer case mounting. Driveshaft out of balance. Excessive pinion ****** runout.
Tire Noise/Vibration
Tire wobble or shudder — • Damaged wheel bearings. • SPIN the tire and CHECK for occurs at lower speeds abnormal wheel bearing play or roughness. ADJUST or INSTALL new wheel bearings as necessary.
• Damaged wheel. • INSPECT the wheel for damage. INSTALL a new wheel as necessary.
• Damaged or worn suspension • INSPECT the suspension components. components for wear or damage. REPAIR as necessary.
• Loose wheel nuts. • CHECK the wheel nuts. TIGHTEN to specification.
• Damaged or uneven tire wear. • SPIN the tire and CHECK for abnormal tire wear or damage. INSTALL a new tire as
necessary.
Tire shimmy or shake— occurs • Wheel/tire out of balance. • BALANCE the wheel/tire
at lower speeds assembly.
• Uneven tire wear. • CHECK for abnormal tire wear. INSTALL a new tire as necessary.
• Excessive radial runout of • CARRY OUT a radial runout wheel or tire. test of the wheel and tire. INSTALL a new tire as necessary.
• Worn or damaged wheel studs • INSPECT the wheel studs and or elongated stud holes. wheels. INSTALL new components as necessary.
• Excessive lateral runout of the • CARRY OUT a lateral runout wheel or tire. test of the wheel and tire. CHECK the wheel, tire and hub. REPAIR or INSTALL new components as necessary.
• Foreign material between the • CLEAN the mounting surfaces brake disc and hub or in the of the brake disc and hub.
brake disc fins. CHECK the brake disc fins for material.
================
This is by Ford for 96, but = to your 95;
Here is a synopsis;
go to:
DIAGNOSIS AND TESTING
Click: Suspension, Front
Refer to Section 04-00 and
Section 00-04.
Click: Components Tests
Noise or Vibration, 4-Wheel Drive Vehicles
Noise or Vibration, 4-Wheel Drive Vehicles
Verify the condition by road testing.
For 4-wheel drive vehicles, verify concern with known quality conventional tires. If symptom still exists, perform the following:
Shift transfer case into two-wheel drive.
Unlock front hub locks (or remove front driveshaft (4602)).
If condition disappears, concern is in front axle or driveshaft.
If condition persists, remove rear driveshaft and road test using front drive.
If condition disappears, concern is in rear driveline or axle.
If condition persists, refer to Symptom Charts in the Diagnosis and Testing portion of this section or other sources.
For front wheel tire concerns, refer to Match Mounting Tires in the Adjustments portion of this section.
Engine Speed Sensitive
The vibration occurs at varying vehicle speeds when a different transmission gear is selected. It can sometimes be isolated by increasing or decreasing engine speed with the transmission in NEUTRAL, or by stall testing with the transmission in gear. If the condition is engine-speed sensitive, the condition is not related to tires.
Front End
CAUTION: Do not attempt to adjust front wheel alignment without making a preliminary inspection of the front end parts, and correcting where necessary.
Fill all fluids to specification.
Make sure spare tire or wheel and related equipment are properly stored.
Remove any excessive accumulation of mud, dirt or road deposits from the chassis and underbody.
Retain all normal loads in the vehicle. Inflate all tires to the pressure specified on the Safety Compliance Certification Label (usually located on the inside driver's door pillar).
Check both front tires and make sure they are the same size, ply rating, and load range.
Inflate all tires to specified pressure (cold). Check both front tires for the same size, ply rating and load range. Refer to Section 04-04.
Check for excessive front wheel bearing end play. Refer to Wheel Bearings, Front, in the Adjustments portion of this section. Adjust and/or replace the front wheel bearings. Refer to Section 04-01A or Section 04-01B.
Check for worn or damaged spindle pins (kingpins) or
ball joints. Replace the ball joints or spindle pins (kingpins). Refer to Section 04-01A (4x2) and Section 05-03A or Section 05-03B.
Ball Joints, Front Suspension Upper Arm and Lower, Twin I-Beam Front Axle Equipped with Joint
Prior to performing any inspection of front suspension lower arm ball joints (3050) or front suspension upper ball joints (3049), adjust the front wheel bearings as described in Section 04-01A or Section 04-01B.
Raise the vehicle and place safety stands under the I-beam axle beneath the spring.
Have an assistant grasp the lower edge of the tire and move the wheel in and out.
While the wheel is being moved, observe the lower spindle arm and the lower part of the axle jaw. A 0.794mm (1/32-inch) or greater movement between the lower portion of the I-beam and the lower spindle arm indicates that the front suspension lower arm ball joint must be replaced.
To check the front suspension upper ball joints, grasp the upper edge of the tire and move the wheel in and out. A 0.794mm (1/32-inch) or greater movement between the upper spindle arm and the upper portion of the I-beam indicates that the front suspension upper ball joint must be replaced
Check for bent steering linkage or excessively worn joints. Refer to Section 11-03.
Check the steering gear mounting bolts and tighten to the specified torque. Refer to Section 11-02B or Section 11-02D.
Inspect the radius arm if bent or damaged. Inspect the bushings at the radius arm-to-frame attachment for wear and looseness. Repair or replace parts as required. Refer to Section 04-01A or Section 04-01B.
Check other suspension components for damage.
Check for aftermarket changes to steering, suspension, wheel and tire components (i.e., competition, heavy-duty, etc.). Specifications in this manual do not apply to vehicles with aftermarket changes.
Shock Absorber Checks
CAUTION: The low pressure gas shock absorbers are charged with nitrogen gas to 931 kPa (135 psi) for 1 inch and 1-3/16 inch bore, and 1034 kPa (150 psi) for 1-3/8 inch bore. Do not attempt to open, puncture or apply heat to the shock absorbers.
All vehicles are equipped with low pressure gas-filled hydraulic shock absorbers of the direct acting type. They are non-adjustable and non-refillable. They cannot be serviced as cartridges and must be serviced as shock assemblies.
Before replacing a shock absorber, check the action of the shock absorbers as follows.
Vehicle Inspection
Check all tires for proper inflation pressure.
Check tire condition to confirm proper front end alignment, tire balance and overall tire condition such as separation or bulges.
Check the vehicle for optional suspension equipment such as heavy-duty handling or trailer tow suspensions. These suspensions will have a firmer ride feeling than standard suspensions.
Check the vehicle attitude for evidence of possible overload or sagging.
Many times front springs and front shock absorbers (18124) are replaced in an effort to solve a vehicle sag concern. Shock absorbers are, by design, hydraulic damping units only, and unlike suspension springs, do not support any suspension loads. Therefore, replacing a shock absorber will not correct a vehicle sag concern.
Road test vehicle to confirm customer concern.
Make sure the shock absorber is securely and properly installed.
Check the shock absorber insulators for damage and wear.
Replace any worn or damaged insulators and tighten attachments to the specified torque (on a shock absorber which incorporates internal insulators, replace the shock absorbers).
Tighten shock absorber attachments to 34-47 Nm (25-35 lb-ft) upper, 60-81 Nm (45-60 lb-ft) lower.
Inspect the shock absorber for evidence of fluid leakage.
A light film of oil (weepage) on the upper portion of the front shock absorber is permissible and is a result of proper shock lubrication. Weepage is a condition in which a thin film of oil may be deposited on the shock outer tube (body) and is normally noticed due to the collection of dust in this area. Front shock absorbers which exhibit this weepage condition are functional units and should not be replaced. Leakage is a condition in which the entire shock body is covered with oil and the oil will drip from the shock onto the pavement.
If leakage exists:
Make sure the fluid observed is not from sources other than the front shock absorber.
Replace the worn or damaged front shock absorber.
Disconnect the lower end of the shock absorber.
Extend and compress the shock absorber as fast as possible, using as much travel as possible. Action should be smooth and uniform throughout each stroke.
Higher resistance on extension than on compression is a normal condition.
Faint swish noises are also normal.
Make sure the part number of the replacement is the same as that of the original shock absorber.
Hoist Check
Noise: Noise can be caused by loose suspension or shock attachments. Verify that all attachments or the suspension components and front springs and front shock absorbers are tight. Replace any worn or damaged upper stud insulators. Check front springs and front shock absorbers for external damage.
Bottom/Hopping: Check condition of the rubber suspension travel stops (front suspension bumpers (3020)). Replace if worn or missing. Examine for evidence of previous overload or damaged components.
Force-Check: Support axle and remove lower front shock attachment. Stroke front shock body using as much travel as possible. The action should be smooth and uniform throughout each stroke. Damping forces should be equivalent on both sides of the vehicle.
Replace only the worn or damaged front shock absorber.
In the past it was recommended that front shock absorbers be replaced in pairs if one unit became unserviceable. Improved sealing, new materials, design and improved rod machining and hardening techniques have added to the reliability of shock absorbers. Therefore, front shock absorbers no longer need to be replaced in pairs when only one unit is not serviceable.
etc.