Jost
- Disconnect the tractor from the trailer. For instructions, see the vehicle Driver's Manual.
- Thoroughly steam clean the fifth wheel.
- Check the mounting for missing or damaged fasteners, and broken components. Replace or repair as needed.
- Inspect the bracket pin bolts. Make sure the locking tabs
are properly securing the bolts in place. See Fig..
Fig. 1, Bracket Pin Bolt Locking Tabs
- Check the fifth wheel for bent, worn, or broken parts. Replace as needed.
- If the fifth wheel is equipped with low-lube plates, check the plates and replace if damaged or worn down to the securing bolts. It is normal for outside edges of the plate to pucker slightly; this does not affect performance.
- Check the fifth wheel adjustment. Using a lock tester,
lock and unlock the fifth wheel several times. Make sure that the
locking mechanism works properly.The lock is properly adjusted if: the wheel locks and unlocks easily each time and the lock tester rotates freely.The lock is too loose if: you feel front-rear play when pulling and pushing on the lock tester handle. See Fig., Ref. A.
-
Checking for front/rear play.
-
Rotating tester in lock.
-
Engage hook.
-
Pull/push handle front/rear.
-
Check for movement of kingpin in lock.
-
Disengage hook.
-
Push/pull handle inboard/outboard.
-
Rotate lock tester.
Fig. 2, Jost Fifth Wheel Adjustment
-
- If the lock is improperly adjusted, correct as follows.If the lock is too tight, loosen the jam nut, turn the adjustment bolt clockwise one full turn, then reset the jam nut. Lock and unlock the mechanism several times to test. Repeat if necessary. See Fig..If the lock is too loose, loosen the jam nut, turn the adjustment bolt counterclockwise one full turn, then reset the jam nut. Lock and unlock the mechanism several times to test. Repeat if necessary. See Fig..
-
Jam Nut
-
Adjustment Bolt
-
Grease Zerk
Fig. 3, Jost Fifth Wheel
-
- If the fifth wheel is equipped with a sliding mechanism,
inspect and adjust it as follows.
- Check the bracket for any cracks or missing and damaged parts.
- Inspect the locking plungers for full engagement.
- Check the locking mechanism for proper operation.If the plungers will not release, check the air cylinder or plunger adjustment.If the plungers are loose, check the plunger adjustment and the plunger springs for proper compression. Replace if needed.
- The outboard slider assembly requires no adjustment. If the plungers are loose, inspect and replace locking mechanism parts as needed.
- The inboard slider is adjustable for frame width and plunger engagement. For adjustment, refer to the fifth wheel installation instructions.
- Replace cracked, worn, or damaged parts with new parts. Replace all loose mounting bolts with 5/8–11 SAE grade 8 bolts, grade C locknuts, and hardened washers. Do not re-use bolts, nuts, and washers on fifth wheel mountings.
- After inspecting the fifth wheel, lubricate all moving parts with a chassis or multipurpose grease. Apply a generous coating of grease to the top plate to fill the grooves, or depressions, on the top plate. See Jost in this manual for lubrication instructions.
Warning: All fifth wheel maintenance, adjustment, and rebuilding must be done only by a qualified mechanic. Improper or incomplete procedures could result in a possible disengagement of the trailer from the tractor, which could result in personal injury or property damage.
Parts are under spring compression. Wear safety goggles while servicing the fifth wheel. Failure to do so can result in personal injury, due to parts ejecting with force.
Warning: All fifth wheel maintenance, adjustment, and rebuilding must be done only by a qualified mechanic. Improper or incomplete procedures could result in a possible disengagement of the trailer from the tractor, which could result in personal injury or property damage.
Parts are under spring compression. Wear safety goggles while servicing the fifth wheel. Failure to do so can result in personal injury, due to parts ejecting with force.