Trans slips in 4H if stuck wheels dont turn

[Gelder]

the first time I noticed this problem I was trying to pull a guy out that was stuck in the woods. I hooked to the truck and had mine in 4 wheel high the engine revved and none of my wheels are turning I put it in 4 wheel low and pulled him right out plenty of torque and power.

the other day while driving in very soft beach sand my truck slowly lost speed and came to a stop in 4 wheel high I revved the engine and none of my wheels were turning had to put it in 4 wheel low does anyone know what could be causing the problem appreciate any help

 

[Gelder]

4H works otherwise but under load wheels don't turn.
Anyone know what could cause this?

 

[p-Bar]

Give em' a chance you'll get some responses. Most of us work

 

[cerberusiam]

Need some info on your truck, year, transmission, mods, etc. Hard to guess when we don't have a list of things to work from.

 

[Gelder]

Sorry. 2005 Ram 2500 4x4. Stock. No mods.
5. 9 Cummins. Appreciate any advice.

 

[Gelder]

Automatic trans

 

[cerberusiam]

Changed the fuel and air filters lately?

 

[Gelder]

Fuel filter yes. Air filter not recently

 

[cerberusiam]

Have you checked the trans fluid lately for fill and color? Does it feel doggy when you are driving it on hard pack roads? If you manually downshift it to 1st does it make any difference?