My wife and I were out in the field the other day and I was bush hogging and on the way back she slid the left side of the truck in a gulley and got stuck. She couldn't get it out so I hopped in and put it 4 wheel drive but the front wheels wouldn't engage. Never had a problem with it before. I got it home and jacked it up and put it on jack stands and engaged the 4 wheel drive and the front wheels would turn but barely and stopped if I put pressure on them. It's a manual engage 4 wheel drive with the shifter beside the gear shifted. There's a round thing right under it with vacuum hose going to it and from what I read in some other post it could be gummed up and not be engaging so I took the vacuum line loose and blowed compressed air into it and could hear it engage and disengage. My question is that where the problem is or could it be something completely different? I need the 4 wheel drive regularly and its not convenient. The trucks got 112k on it.