I have a 96 Monte Carlo Z34, and the converter doesn't lock up, it has 186000 on the clock. When I am running at 62-64 mph the tach reads 2200, if I start up a gradual hill the tach will go to 3000 or more and never seams to lock up. The car will sometimes miss 2nd gear, it starts off in first then its like I put it in neutral the engine revs up so I let off the gas it catches second and shifts normal the other two gears. I have been driving cars with the four speed auto for some time now and can always tell when the converter locks up. I have a 94 Vette, and when I'm running at 64 in it the tach reads 1600 also a four speed auto. The final drive in the Monte is 3.43, and the Vette is 2.59 so I can see a little more RPM in the Monte, however I don't know what the OD is in the Monte the Vette is .70. I would appreciate any and all suggestions for this problem, Thanks..................Notech52