Hey guys,

I learned something this weekend. Some of you guys may already know this but I will post anyway.

I had a vacuum leak in the line that feeds the vacuum to the transmission (2sp Auto Jetway). That leak was causing a very loud banging/clunking when the car decided it was time to down shift while slowing to a stop. Once the vacuum leak was found and fixed, the bang/clunk went away. It is so smooth now, I have to really try to hear/feel it.

 

Yes, I had the same issue by a different reason when I first bought my Cutlass. The modulator was connected to ported vacuum. When I moved the line to manifold the issue went away.