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7.2.2 – Uncoupling Twin Trailers
Uncouple Rear Trailer
- Park rig in a straight line on firm level ground.
- Apply parking brakes so rig will not move.
- Chock wheels of second trailer if it does not have spring brakes.
- Lower landing gear of second semitrailer enough to remove some weight from dolly.
- Close air shut-offs at rear of first semitrailer (and on dolly if so equipped).
- Disconnect all dolly air and electric lines and secure them.
- Release dolly brakes.
- Release converter dolly fifth wheel latch.
- Slowly pull tractor, first semitrailer and dolly forward to pull dolly out from under rear semitrailer.
Uncouple Converter Dolly
- Lower dolly landing gear.
- Disconnect safety chains.
- Apply converter gear spring brakes or chock wheels.
- Release pintle hook on first semitrailer.
- Slowly pull clear of dolly.
Never unlock the pintle hook with the dolly still under the rear trailer. The dolly tow bar may fly up, possibly causing injury and making it very difficult to re-couple.
7.2.3 – Coupling and Uncoupling Triple Trailers
Couple Tractor/First Semitrailer to Second/Third Trailers
- Couple tractor to first trailer. Use the method already described for coupling tractor semitrailers.
- Move converter dolly into position and couple first trailer to second trailer using the method for coupling doubles. Triples rig is now complete.
Uncouple Triple-Trailer Rig
- Uncouple third trailer by pulling the dolly out and then unhitching the dolly using the method for uncoupling doubles.
- Uncouple remainder of rig as you would any double-bottom rig using the method already described.
7.2.4 – Coupling and Uncoupling Other Combinations
The methods described so far apply to the more common tractor-trailer combinations. However, there are other ways of coupling and uncoupling the many types of truck-trailer and tractor-trailer combinations that are in use. There are too many to cover in this manual. You will need to learn the correct way to couple and uncouple the vehicle(s) you will drive according to the manufacturer and/or owner specifications.