Pinpoint Test B: The Transfer Case Does Not Shift Between 2H and 4H Modes Correctly
Four Wheel Drive (4WD) Systems - Mechanical Shift
Pinpoint Tests
Pinpoint Test B: The Transfer Case Does Not Shift Between 2H and 4H Modes Correctly
Normal Operation
Provided the manual hublocks are set to LOCK, the transfer case lever position is the only input required for shifting from 2-Wheel Drive (2WD) high (2H) to Four-Wheel Drive (4WD) high (4H)/4WD low (4L) with the engine off. When the engine is running, shifting the transmission to NEUTRAL eliminates drag torque created by the engine, allowing a 4L shift to occur. Applying the clutch on manual transmission equipped vehicles is not required for shifting to 4L. The Mode Indication Switch (MIS) communicates the transfer case shift lever position to the Instrument Cluster (IC). Systematically check the internal components of the transfer case and shift lever, manual hublock components and front axle.
This pinpoint test is intended to diagnose the following:
- Shift lever assembly
- Transfer case internal components
- Manual hublocks
- Front axle assembly
PINPOINT TEST B: THE TRANSFER CASE DOES NOT SHIFT BETWEEN 2H AND 4H MODES CORRECTLY
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B1 CHECK THE TRANSFER CASE SHIFT TO 4H
- Turn the LH and RH manual hub to the LOCK position.
- Shift the transfer case shift lever to 4H.
- Execute tight turns on a hard surface.
- While the vehicle is in motion, check for the presence of driveline wind-up and tire scuff.
- Are driveline wind up and tire scuff present?
Yes
GO to B2.
No
GO to B3.
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B2 VERIFY THAT THE TRANSFER CASE IS NOT IN 4L
- Drive the vehicle with the transmission in 1st gear.
- Observe the vehicle speed and engine rpm.
- Is the vehicle in 4H?
Yes
GO to B5.
No
GO to B4.
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B3 CHECK THE TRANSFER CASE 4H ENGAGEMENT
- With the transmission in NEUTRAL, position it on a hoist. Refer to Vehicle Jacking and Lifting.
- Shift the transfer case.
- Shift lever to 4H.
- Rotate the rear driveshaft while observing the front driveshaft.
- Does the front driveshaft rotate?
Yes
GO to B6.
No
GO to B4.
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B4 CHECK THE TRANSFER CASE INTERNAL 4H ENGAGEMENT
- Disconnect the transfer case shift linkage.
- Manually shift the transfer case sector shaft to the full counterclockwise direction, then rotate counterclockwise one position while turning the rear driveshaft.
- Rotate the rear driveshaft while observing the front driveshaft.
- Does the front driveshaft rotate and 4H shift occur?
Yes
INSTALL a new shift lever assembly. REFER to Transfer Case.
No
REPAIR the transfer case. REFER to Transfer Case.
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B5 CHECK FOR MANUAL HUBLOCK ENGAGEMENT
- Rotate the left front tire one revolution forward and one revolution backward while observing the LH front axle shaft.
- Rotate the right front tire one revolution forward and one revolution backward while observing the RH front axle shaft.
- Did the LH and RH axle shaft rotate?
Yes
GO to B6.
No
CHECK that all driveline fasteners are present and tighten to the correct specification. REFER to Differential Assembly for further diagnosis of the front axle.
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B6 CHECK TRANSFER CASE INTERNAL 2H DISENGAGEMENT
- Disconnect the transfer case shift linkage.
- Manually shift the transfer case sector shaft to the full clockwise direction while turning the rear driveshaft.
- Rotate the rear driveshaft while observing the front driveshaft.
- Did the 2H shift occur and the front driveshaft remain stationary?
Yes
INSTALL a new transfer case shift lever assembly. REFER to Transfer Case.
No
REPAIR the transfer case. REFER to Transfer Case.
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