Is flairing bad?
 

I got my car back from the shop having had to have the modulator replaced, and now it flairs. It never did before. Can it cause problems? I think I will take it back if it is a problem.

Yes, fl;aring is bad. Yes I would take it back to the shop. Adjustment should be part of replacement.

Check the fluid level before you take it back. My 380Se flared on me on the way to the MB dealer and I found that the fluid level was way down. It got me home, but I filled it up and everything has been fine since, but I check it frequently.

Yeah, check the fluid; be sure it's fully warmed up, or it will read low.

Sounds like they just didn't adjust the modulator valve.
To really do it properly, they should attach a pressure gauge to the tranny and set the modulator to spec (varies by year and type, but usually in the 50-60 psi range). There is a model vs pressure chart somewhere in the archieves here, but I don't remember where I saw it. Maybe search under "modulator pressure". A 5-lb variation in pressure can noticeably affect the shifts.

Flairing is definitely not good longterm. It allows the engine to rev up between each shift, and the tranny clutch plates have to slip as they bring the revs back down - extra wear on the plates.

DG

I will check the fluid before I go back to the shop. I have a copy of this chart. I just could never find the bolt needed to make the pressure gauge
to see what the pressures were so I just took it in after the bolts stripped out.