1986 420 SEL shifting roughly

My wife took the car to Missouri from Indiana. When she came back I could feel that something has gone wrong. She said that she felt that while driving in the mountains, she felt all of sudden it started shifting roughly.

Now I am concerned if this is a major expense or not. As I am slowly accelerating, I could feel a noticable jerk everytime it shifts from 2nd to 3rd and then from 3rd to 4th. When I slow down at the light, the down shift to 1st is also very noticable. Any help would be very apperciated.

There is a vacuum line that is routed from the rear of the engine to the modulator valve and is resposible for giving the signal that tells the trans how hard to shift. If the line is cracked or the ends where it attaches to the engine and modulator are loose the shift quality will be harsh...You also could have a bad modulator valve or the cap also falls off on occasion.
Good luck

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
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