My 91sl500 would not shift into 2nd and the mechanic said to bring it in, and during the drive, not to take it above 3000rpm. Upon inspection he said I had dirt in the shift valve but the fluid was very clean. Next day he called and said he cleaned the valve but that was not the problem, I needed a new transmission. Still, after the new transmission, the car is doing the same! It will not shift into 2nd until a little over 3000 rpm. After that, when it's warm, it is fine, and shifts fine for all additional trips that day. However, the power I used to enjoy is gone - it's like the car has been castrated. After the new transmission, I have taken it back twice, the mechanic says he cleans the shift valves, but the next morning (while cold) it does the same. I am out $3000 and the problem is not solved.