Rubicon Express RE8000 User Manual
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< UNI-BODY END) – PHOTO 5 - AXLE END (ZERK ON TOP) >
PHOTO 6
TROUBLESHOOTING
Rear driveline:
Acceleration vibration: Caused by the pinion being too high in relation to
the transfer case output shaft. Adjust upper control arm to lower pinion
accordingly.
Deceleration vibration: Caused by the pinion being too low in relation to
the transfer case output shaft. Adjust upper control arm to raise pinion
accordingly.
Slip yoke vibration: Caused by excessive angle on the transfer case slip
yoke. Very common on vehicles with 2” or more of lift. This can
sometimes be cured on 4.5” lifts with NP231 or NP242 transfer cases
with the included transfer case drop kit. Note that pinion adjustment may
also be required - see acceleration and deceleration vibration
troubleshooting above. For best performance on NP231 or NP242 t-
cases, install a slip yoke eliminator (SYE) kit and rear CV drive shaft. For
best performance on NP249 t-cases, install new yokes and a standard
two ujoint front drive shaft, and an SYE kit and rear CV drive shaft.
Adjust rear pinion so it is 2 degrees below parallel with CV drive shaft
(see acceleration and deceleration vibration troubleshooting above).
A
transfer case drop kit can usually be omitted with these drive shaft
changes.
High speed wobble:
This is fairly common with y-type steering on lifted ZJ's. It is a condition
where front tires will shimmy after hitting a bump. Avoid bias ply tires
and wheels with excessive offset. Check for worn or loose parts. In most
cases a reduction of positive castor will eliminate this condition. A good
rule of thumb is minimum factory caster and maximum factory toe in.
Note that lift heights increased with coil spacers (or taller coils) may
exhibit wobble that cannot be corrected with alignment.
Bump steer:
Caused by improper relationship of drag link and track bar. To correct,
center axle again following the instructions supplied with the track bar.
Next determine the neutral position of the steering wheel. Adjust the
drag link to center the steering wheel.
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