I know its probably not like a BTS valve body or a BTS tranny but the Sonnax seems to be pretty good. If the Sonnax is supposed to firm up the shifts, it certainly has done that. As a matter of fact, it almost feels like a manual on some shifts and I hope that its supoosed to feel that firm because its pretty dang firm sometimes.

 

I have the sonnax valve and triccumulator springs in my valve body. The shifts are considerably firmer. I really notice it when towing my fifth wheel. It is firm, but not overly aggressive. I was worried that the increase in line pressure from my DP Tuner chip would make the shifts even harder, but they feel normal (quick and precise). Actually, the chip eliminated the "sluggishness" of the TQ converter lock-up.