Loss of traction at speeds of 40-65...

Your truck has more torque than traction.

 

hy·dro·plane
/ˈhīdrəˌplān/

verb
NORTH AMERICAN
gerund or present participle: hydroplaning

1. (of a vehicle) slide uncontrollably on the wet surface of a road.
   "a motorist whose car hydroplaned and crashed into a tree"
2. Could be the road has a different mixture of asphalt and the oils surface when it gets wet. Leaving a thin film of oil over the water and road. Causing the same as 1 above.

 

Is it a single drive axle with a dummy axle?

 

What brand of tires do you have?I run on 287 a lot,some places will get slick when it rains.It does that out in Odessa also.
If your trailer tandems are too far forward it can also take too much weight off your drives,there are a lot of things that can cause tire spin.

 

The same stretch of highway in similar conditions causes you to lose traction.
What is going on is you are learning the road and where to take it real easy.

If you are paying for the tires, maybe you should pay more for better tires.
If the company is paying, then learn to deal with it.

That's why, as a company driver, I shut down at the earliest sign of poor traction conditions.
The tires on these trucks are not designed for those conditions.

 

Do you have air suspension?

I had a truck with a tag axle that had bags that were over inflated.

 

If it’s only on that section of road and doesn’t happen anywhere else, it’s going to be the road. Roads can get what’s called ponding during a rain and that just means water pools up or puddles up on the road surface.

Interstate 40 does this between durham and Greensboro in NC. There’s multi vehicle pileups on that stretch all the time.

I like to slow down when it rains. Mostly because others dont and they’re driving reckless. But also because it can be hard to see the ponding and id rather not wreck trying to race to the inevitable stopped traffic ahead.

“Open shoulder tires” can help in rain and mud and snow but you’ll get a decrease in MPG.

 

What are you going 60 mph in the rain for anyway?