movie in Pacific Northwest with helicopter turned into monster truck

I saw this movie in the theater probably in the mid-1980's.  The only thing I can remember is that it involved a crew of around eight people somewhere in the Pacific Northwest on some misadventure.  I'm about 80% sure they were pitted against some bad guys, but perhaps the movie's antagonist was just nature and the elements.  The most distinctive scene involved a small helicopter they accidentally wrecked partway through the movie.  They couldn't fix it, but they had some large truck or tractor tires and they cut the walls off of two of the tires, mounted two axles under the body of the helicopter, cut the tail off the helicopter and removed the overhead rotor, then stretched the treads from the tires to make bulldozer/tank tracks running between the axles, converting the helicopter fuselage into a makeshift all terrain vehicle.  Can someone please tell me what this movie is?