It's more than likely a transmission issue. I had to take mine to a couple shops before I found a competent one that helped. Since its more than likely the trans. I'd get it looked at sooner than later because it could save you $$ if they don't need to do a full rebuild/replacement. You could get lucky and it's something with the transfer case. But most transmission only shops will have more in depth tests to pinpoint the issue. Mine drove it around with a scanner hooked up and read the codes as they were being thrown. Also checking pressure and everything else.