I have a 1986 560 SL(722.313). It will not shift into 4th gear except under the following conditions: Accelerate to 70 mph and it shifts automatically or at 40 mph move shifter to N and then back and it will be in 4th. I have replaced filter and fluid and have inspected valve body for any problems. I also adjusted throttle cable. The tranny was rebuilt one and a half years ago. Any ideas?