Got into some soft ground and needed to spin the tires clear, in 4LO it seemed to almost dead pedal and cut power as if TC was on(in 4lo its off). Swapped to 4HI, kicked TC fully off and was able to spin the tires at speed to clear the treads. Can't seem to find if this is normal? I would assume(i know i know) if this is normal, it is to save drivetrain? I did also have the loaded hay trailer hooked up, and wasn't exactly light weight(7k ish).

 

Year, make, model...?

 

You have a 2019 5 L.
Leave TC alone, put in 4 Lo and turn on rear E-Lock by pulling the **** outward.
I have a 2018 5 L that should be the same.
Never had an issue like I understand you to describe.
4 Lo won't spin the tires faster. Only overcome what traction there is more easily.
Only engine will rpm faster. under 4 Lo gear reduction.
In 4 Lo the engine speed is program changed to account for this and generate more pulling torque, >>> to all 4 wheels. if traction is available...
Likely TC switched off did some control you did not expect.
There is a chart in the Owner Manual on TC control usage.
Good luck.

 

Sorry guys thought I had updated all my pickup information. Its a 24 PB now not a 19. I had the rear locked, and the main reason I went for 4lo was to be a little easier on the trans when in the muck with a trailer. It was definitely derated or cutting power. I don't believe TC functions at all or will even turn on(didn't try that...) in 4LO. So thus why I'm curious on this one.

 

Only thing I can think of is the truck detected a trailer connected and maybe limits or restricts power in 4LO with a trailer on the back. I can see that being the case (self-preservation). I imagine that the stress on certain components would be astronomical with that level of torque multiplication and say a 10k lb. load on the back. Next time, try disconnecting the trailer harness, it might help you out.