Is the 377 a light duty rig???

Sorry, I changed jobs since this post. I ended up being the truck driver AND the mechanic for these trucks I drove.
The issue with the 377 that I found was the airbags were dry rotted and weakened. I replaced the air bags on the truck and the loads became so much easier to lift. If anyone was pondering, I was operating an RGN, so I had to deflate to help drop the trailer.
The company I worked for didn't want to spend any money to fix the trucks, so I ended up going back OTR. The events leading up to me leaving that company were funny, and then sad (for me)...
This incident with the airbags, I brought the truck and trailer back to the shop, they told me it was holding air just fine, so I said, "Okay, allow me to demonstrate!" I commenced to loading a 30K# tractor onto the trailer, hooked up the RGN, and went to lifting the load. I got the trailer to my preferred ride height, and waited. To help speed things up, I idled up to 1,500 rpm. It took almost 30 minutes of all of us standing and waiting. They looked at me and said, "See, it's holding air!" At that exact moment when they finished their sentence, both of the rear air bags popped, and then the front ones went! I looked at them and said, "Yeah, they're holding air real good!" That made my day...
More penny pinching later, and I quit because they wouldn't get my trucks DOT compliant. 2 OOS violations in one month later, and I told them where they could stick that job...
But in reply to the thread, it turned out to be the airbags, as odd as that sounds. Thanks for all your comments and suggestions!
Everyone keep the bugs off your glass, and the bears off your ###!