I bought a 96 Tahoe 2 wheel drive 5.7liter with a blown engine. I also had a 95 Tahoe 4WD that was wrecked that I just put a new engine in. So I took the engine from the 95 Tahoe 4 wheel drive 5.7liter and put it into the 96 Tahoe 2 wheel drive. I find out the 96 was a vortec engine and the 95 is not so I switched out the ECU and wire harness. Everything runs great on the engine but the transmission will not shift correctly. The wire harness is from a 4 wheel drive and the transmission I have it hooked to is a 2 wheel drive, could this cause the problem? I have been thinking about buying a 2 wheel drive ECU and wire harness but dont want to spend the money if that is not the issue. The engine and transmission are new so I know that is not the problem.