Trailer Coupling Question

A bit confused about the order when coupling with air bags. In school the one day we did some coupling, one instructor had us back part way under the trailer and then raise the bags. I didn't like that because from what i have seen and read, says of course that the trailer should be lifted slightly when you back under it. I of course did as I was told :D Whats the deal?

Deflating the air bags and then inflating them really isn't needed. The only time I deflate my air bags is when the driver who dropped the trailer didn't crank the landing gear high enough.

How I taught it was like this.

Back under the trailer, but not all the way. Get out to make sure you won't jump the fifth wheel with the kingpin. If it checks out okay then back under it. The trailer should in fact lift up slightly when you back under it.

I was taught the same way as Daniel B. said then I was also taught the acronyms Pal for hooking up P for pin stop prior to completely backing under trailer for pin alignment and height A for airline and electrical connections and L for raising landing gear The Lap for disconnecting the trailer L for lowering Landing gear A for disconnecting airline and electrical connections and P for releasing king pin I do that way every time and it has helped me out.Is it right or is it the way everyone should and or does do it I am still to new to tell you but it has helped me remember the steps I need to take.

Yep just like Daniel says. I drop trailers of all kinds and most of them do not have landing gear but when I get one that does I crank it down until the landing gear touches the ground and then give it another crank just until it starts to lift off the truck. You will see the suspension start to rise. Then I pull out from under it and it drops maybe 2 inches off the 5th wheel. This leaves you plenty to get back under the trailer without changing your suspension level. The others I drop are lowboys so they do not count in this situation.

Swift teaches lowering the bags before backing under the trailer as well as when you unhook one. However, in my road training my instructor never lowered the bags, in fact most of the time he did not GOAL the hookup.

I partly followed his lead. I do GOAL, but the bags stay the same. (BTW: Do what you need to do to get through school, of course! Follow what the school teaches while you're there.) I do watch the mirrors & see the trailer lift a bit as I back in - sometimes that little lift takes a bit more juice on the accelerator, too.

Thank you.

If you're dumping your suspension - you'd better GOAL.

If you "high-side" the 5th wheel, because the trailer was TOO HIGH (for dumped bags) and the kingpin goes OVER the 5th wheel, and gets stuck in front of it - this can be TONS OF FUN to get off.

At least if you high-side a trailer with the bags FULL - you can try to dump them to get the trailer "un-stuck" (along with raising the landing gear some more to give you enough hight to clear the kingpin OVER the 5th wheel plate).

I have seen this happen in yards - where they had to get a forklift (or a yard truck with a hydraulic 5th wheel) to lift the trailer so it would clear. Which means it's REALLY IMPORTANT to check trailer height in yards that use "spotters" (yard mules with hydraulic 5th wheels) because the spotters almost never check trailer height when they drop the box (and they never touch the landing gear), because they just raise and lower their 5th wheel.

The funny part is - in the CDL Written tests - they simply say "the trailer might not couple properly" - they've obviously never seen a kingpin go over the top of a 5th wheel and get stuck.

Rick

If you're dumping your suspension - you'd better GOAL.

If you "high-side" the 5th wheel, because the trailer was TOO HIGH (for dumped bags) and the kingpin goes OVER the 5th wheel, and gets stuck in front of it - this can be TONS OF FUN to get off.

At least if you high-side a trailer with the bags FULL - you can try to dump them to get the trailer "un-stuck" (along with raising the landing gear some more to give you enough hight to clear the kingpin OVER the 5th wheel plate).

Rick

Happened to me! Fortunately my instructor, Carlos, was able to show me what that over-shot looks like. I lowered the bags, Carlos cranked up the gear to I could pull up.