Loud "exhaust" sound when accelerating and no evidence of an exhaust leak exists? Check.
Rough gear changes, especially during spirited driving? Check.
"Engine" vibration when idling in gear, but the engine mounts are solid? Check.
Looks like it's time for me to change the transmission fluid.
I used an easy three-part process to service my transmission fluid. The fluid change takes a total of 30 minutes, divided in three ten minute parts.
First I used my vacuum pump to suck out the old transmission fluid.
I got almost three quarts out on my first pass. I had let the fluid get a little low because a little more than 3 quarts can be drained this way. I then refilled the sump with three quarts of Valvoline Max Life, but any quality Dextron III or compatible ATF fluid will do.
I then drove to work and back before draining/refilling the fluid for a second time. I drove to school and back before draining/refilling the fluid for a third and final time. This final time I added about 3.2 quarts instead of just 3, to top the sump off to the recommended level.
This gently replaces the bulk of the 7.5 quarts inside the transmission. I have read cautions against aggressively flushing the transmission on the 9-5. People have reported problems with valves sticking and seals leaking after having their transmission flushed. The process I used is supposed to prevent these possible issues.
Renewing the fluid made the car drive quieter, softened the shifting, and reduced vibration (especially when backing out of the garage and parking spaces).