Best to keep an eye on it. Removing the battery cables will clear DTCs such as P1811. The P1811 setting is what causes the tranny to whine because maximum line pressure is commanded on.
Update: So far to date on my '99 Regal LS with over 236K miles no more P1811, whine or harsh upshifts so the shift kit mod helped. Recently I too had to replace the original alternator. But after replacement picked up a SES light and P0741 DTC.
The TCC is "stuck off". Basically the TCC is not locking up after it shifts into 4th OD above 45 mph. The rpms are supposed to drop an extra 200 rpms or so. Troubleshot and determined a valve body issue with the TCC-PWM solenoid/valve. TCC-PWM solenoid coil ohms out good (10-12 ohms) and all wiring between the transaxle and PCM module. So adding 8 oz. Seafoam to see if I can get the valve body cleaned out. No plans for a rebuild. As far as driveability it runs a few hundred rpms higher when cruising and noted a minor gas mileage loss as a result.