Kevin in Atlanta

Chasing and finding vacuum leaks on my son's 87S4.

Surges really bad in reverse. Neutral and park it is very slight - hardly noticeable.

Any ideas?

Herman K

Check the vacuum line that run from the engine bay to the transmission modulator valve with a Mity-Vac to see if you don't have a vacuum leak in this line if there no leak there should be issue at all.

If there is a small leak the mechanical action of a small amount of movement (flexing) of the engine/tt/transmission on it's flexible mounts may result in a different size gap in the line

Kevin in Atlanta

I will do that!