I have had a hard second gear shift on my TH400 since I got the car 5 years ago. I just decided to address it. I checked fluid level, vacuum at modulator is 15 and engine is tuned but problem exists. I bought a B &M adjustable modulator. After install no difference. I adjusted it out two turns and it was a little better. I was going to back it out some more but am afraid of damaging the tranny. I'm below novice level on transmissions. This was my last attempt before buying another transmission.