Some of he most interesting stories I heard from old timers came from a senior driver who was just about to retire at the time I got my Texas Chauffeur License in the late 1970's. He spent most of his driving career driving Houston to El Paso and back. He mentioned that in the late 1930's, the trucks were so underpowered that on a hot day, he wouldn't be able to pull some of the grades around Junction or other spots on old US 90. The solution was running 2 trucks together at all times. When the trucks would not make it up, they would unload drums until they could. Then, they would make the climb, offload a like amount, and return to their temporary "warehouse." Load up the offloaded drums (using a 2 wheeler and a ramp for the stake bed flatbed trailers, get back to the top, reload the rest, and proceed onward!) People think they have it tough these days, ha! No sleeper berths back then either, but if there were no bunks available at the truck stop a hammock under the trailer was always in the truck ready to go. I'm retired now long ago, and my wild but true stories are a bit less wholesome!
I can tell you a dozen different stories of my family members or their running buddies changing transmissions, diffs, or whole axle housings out on the side of the road during the 50’s,60’s, and 70’s. No one knew what roadside service was back then and heavy wreckers were few and far between, so you just fixed it where it came to a stop. Imagine a 1957 VW beetle making a 500 mile trip from home base with an RTO12513 in its trunk to swap out in a White-WesternStar cow truck stuck up in the Tejas Pan Handle. The driver already had the trans dropped and sitting on the ground before grand pa got there. He had run a 4x4 across the doors thru the open windows and chained it up after removing the seats and floor. WW2 generation of truckers were McGyver’s.
If you broke down in the 1970's or 80's, the next driver coming down the road would stop to assist, even if it was no more than getting the info to call for help at the next pay phone and notify the company or whomever to get help on the way. As decades passed, now you are lucky if they don't run you over...