Most of not all trucks are equipped with a switch to let the air out of the rear suspension, which lowers the 5th wheel. Most drivers that I know of crank the legs until the legs are on the ground and then back up a half to a full turn. If you do it until the way the book says the trailer will probably be high next time someone has to hook it.
Not all trucks have the air bags air dump switch. the 2012 cascadia i trained on did not.
Just lowering the legs doesnt always leave enough room either. One of my trainees lowered the legs and pulled out but the tires got stuck when the fully loaded trailer dropped on them. we couldnt move the legs cause the load was too heavy, and the tires just spun and were rubbed against the trailer. i couldnt pull out and couldnt get back under it.
The best method i know is to drop the landing gear until you hear a "sheeeeesssshhh" of air. At this point you know the pressure has been removed from the 5th wheel. then pull out.
Not all trucks have an air dump switch. I always lower the gear and give an extra crank until i hear my airbags hiss to know I have taken some weight off and uncouple. I know many drivers in my company lower the legs until about 1" from ground and drop the airbags and pull away. The problem with that is if the next guy does not have a air dump, the trailer might be too low to couple and will need to be raised to get under the 5th wheel. A loaded trailer is alot harder to raise then it is to lower it. Had a trailer last week that was so low I had to dump my airbags just to get my frame under the trailer and use airbags to lift it to make cranking the handle easier.Something else to think about, if you are driving an auto-manual it is to couple and not ram the kingpin when you take weight off the 5th wheel.
We have the airbag dump and we are instructed to lower the landing gear until it is about an inch off the ground, dump the air bags and pull out. Reverse to hook. Our drives are not higher than our frame.
When uncoupling an empty, crank until the sand shoes or pads on the end of each landing gear legs are about 1/2-1” above the surface of where you are spotting the trailer. I never dump the air when empty.
For a loaded trailer once the pads touch the ground, add a half to 3/4 turn on the crank. If I dump the air it’s only at the point when the trailer is almost off the fifth wheel.
The above suggestions accomplish two things; sets the height of the trailer at an optimal level for the next driver to get under it. And positions your fifth wheel at a downward angle to better align to get under your next trailer.
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When uncoupling the CDL manual instructs you to turn the handle a few extra turns to take weight off the fifth wheel. I watched a SWIFT driver couple with a Target trailer and mentioned this to him. He told me NOT to do that because vehicles built after 1995 have a way to lower the suspension on the drive wheel axle. Is this true for all newer?
CDL:
Commercial Driver's License (CDL)
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