Pinpoint Test M: Straightline Driveline Wind-Up
Four Wheel Drive (4WD) Systems - 2-Speed Torque-On-Demand
Pinpoint Tests
Pinpoint Test M: Straightline Driveline Wind-Up
Normal Operation
In order for the Four-Wheel Drive (4WD) system to function correctly, tires and wheels must be the same size, be in good condition and the front and rear axle ratios must match.
This pinpoint test is intended to diagnose the following:
- Unmatched tire sizes
- Unequal amounts of tire wear
- Unequal tire inflation pressures
- Unmatched front and rear axle ratios
PINPOINT TEST M: STRAIGHTLINE DRIVELINE WIND-UP
NOTE: 4X4 HIGH/LOW is not intended for driving on hard/dry surfaces.
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M1 VERIFY THE CONCERN
- Drive the vehicle and shift from 4X4 AUTO to 4X4 HIGH. There should be minimal wind-up in 4H mode during straightline maneuvers, (wind-up in turns is normal; 4X4 HIGH/LOW is not intended for driving on hard/dry surfaces).
- Is excessive wind-up present?
Yes
GO to M2.
No
RETURN the vehicle to the customer. ADVISE about correct 4WD system operation and normal vehicle behavior.
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M2 ISOLATE TRANSFER CASE
- Disconnect all wiring going to the transfer case and road test.
- Is excessive wind-up present?
Yes
CARRY OUT the 4WD Functional Test. GO to Pinpoint Test P. Pinpoint Test P: Four-Wheel Drive (4WD) System Functional Test
No
CONNECT the transfer case wiring and GO to M3.
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M3 CHECK FOR MATCHING WHEEL AND TIRE SIZES
- Check the wheel and tire sizes.
- Do the 4 wheel and tire sizes match?
Yes
GO to M4.
No
ADVISE the customer that 4WD systems require 4 matched, correctly inflated, correctly maintained tires to operate correctly.
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M4 CHECK TIRE INFLATION PRESSURE
- Check the inflation pressure in each tire. Refer to Vehicle Certification (VC) label.
- Are the tire inflation pressures correct?
Yes
GO to M5.
No
ADJUST the tire pressure as necessary. TEST the vehicle for normal operation. ADVISE the customer that 4WD systems require 4 matched, correctly inflated, correctly maintained tires to operate correctly.
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M5 CHECK THE TIRE CIRCUMFERENCE
- Using a tailor's tape or flexible measuring tape, measure the circumference of all 4 tires and record the measurements.
- Calculate the average of the circumference of the 2 front tires and 2 rear tires.
- Is the difference between the 2 averages or the side to side measurements greater than 13 mm (0.5 in)?
Yes
REPLACE the smallest circumference tire(s) and REMEASURE tire averages. REFER to Wheels and Tires for additional information.
No
GO to M6.
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M6 CHECK THE FRONT AND REAR AXLE RATIOS
- Check that front and rear axle ratios match. Refer to Differential Assembly &/or Axle Shaft Assembly &/or Drive/Propeller Shafts, Bearings and Joints.
- Do the front and rear axle ratios match?
Yes
RETURN the vehicle to the customer and ADVISE about correct 4WD usage and normal vehicle behavior.
No
CHECK the vehicle identification label. INSTALL the correct axle(s). REFER to Differential Assembly &/or Axle Shaft Assembly and Differential Assembly.
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