That's called being upside down on a loan, and unless you can sell it to an individual for way more than it's worth (which I don't recommend even if you can get away with it because it's not right...), you might be stuck with it.
Many car dealers will offer to pay off your loan if you buy a new car, but don't go for this offer until you read every bit of fine print and are 100% sure you understand the terms. Know the value of the car you are negotiating for and do the math! There's no free lunch. Somebody is going to pay the loan, and chances are it will be you, one way or another.
The best advice I can give you is to take good care of your truck and drive it as long as you possibly can. With proper maintenance and good driving habits, a vehicle can easily reach 200,000 miles. Depending on how much you drive this will give you 8-10 more years, so once you pay off the loan you can drive it for free for a few years and make back the lost money.
I like to get as much value from a car as I can before I absolutely have to get a new one. You can save a lot of money this way. My wife, on the other hand, wants a new car every two or three years, so there goes all the money I save. LOL
One last idea...check the interest rate on your current loan. If it's too high, see if you can refinance for a lower rate. It will save you a lot.