Auto Trans Downshifting Sluggish

backfrom60s

I have a 2004 B2300 p/u with only ...... 67,000 miles. I was very lucky to find it. It’s super clean inside and out, and rides, handles, responds, and looks just like a vehicle with such low mileage should. It has one flaw, however. If I slow down to turn, or because traffic requires it, then reapply a bit of throttle, there is a short delay before the tranny responds (downshifts), and the shift is fairly hard. It seems to upshift gently and smooth, but lags on the downshift.

I my day, I would have said it needs a new vacuum modulator, or has a vacuum leak. Is this the way it’s still done in this era of digital everything? Or does someone have an idea?

Thanks