Cadillac Repair: SLS transmission, accelleration, steady speed

Question
What would cause a 1996 SLS transmission to slip going into 40 miles per hour.

Answer
Hi John, To answer your question I would need to know if you are changeing gears and what gear you are going into. Also are you at a steady speed, accellerating hard like trying to get on the highway or in town mild accelleration when the slip is happening. If there is a check engine light on or had come on and the codes could be read that would help also. Thanks, Bill