Why is the automatic transmission on my 1987 Mercury Grand Marquis not shifting properly any more?
since Wednesday last week the 4 speed automatic transmission on my '87 Mercury Grand Marquis does not shift properly any more. Lower gears at lower speeds (up to 40 mph) seem to work properly, However, when trying to accelerate up to 70 mph, the.engine is speeding up, but the transmission stops shifting. Max. car speed is limited to approx. 45 mph. What can be the cause and what can I do here ? Thanks for any support, Peter