My friend has a 1996 K1500 with a 4L60E. The 2nd gear does not work at all. The 1st gear works fine, then it will skip 2nd as he accelerates and then drops into 3rd. Once in 3rd, if the transmission downshifts into 2nd it will just rev the engine and not go anywhere. If he lets off the gas some it will shift back into 3rd. All gears except 2nd work real well, and the transmission locks in tight with no slipping in the other gears. Where should we start looking for problems?