I was backing my suburban and trailer up and switched from drive to reverse and when stepping on the accelerator it feels like it'* engaged in reverse, but there is something stopping it from moving. Put it in drive and same thing. Put it in neutral and try to push it and again something feels like it'* preventing it from rolling like something blocking gears from spinning. I jack it up and the wheels spin freely. Let it back down and they're stuck again. Any insight would be very appreciated.

How may rpm are you taking it to?

Not much. Probably not more than 2000. It feels like it'll go if I give it enough gas, but with the way it feels. Doesn't sound like that'* a good idea.

Sounds like something going bad inside, like valve body leaking etc. How many miles on it?

With the engine off and in neutral,does the vehicle roll? Does it drive in neutral? can you determine if it is rear diff or internal trans. Have seen both causing a tie -up.