I have my line pressure all the up with my shift kit and that bitch hits hard like its suppose to. If you are worried about it quiting you might as well turn the line pressure up.

 

Start with the "simple to access" item(s) first... servos. Make sure the seals aren't damaged, no grooves in the case that would allow porosity, and am assuming you're using the proper apply pin. Seems I remember my Sonnax servos came with a slightly longer apply pin. I'm not sure about pin length though.

I wouldn't attempt to increase pressures until you're sure there's no mechanical solution. Good luck.

 

The TM has been removed completely and the line pressure is set to stock.

I didn't replace the apply pin but I haven't seen to many people replace them for most of the installs I was able to find. Is there a way to check it without any specialty tools?

 

I don't know the different lengths, but do remember talking with somone about having the longer pin. You know who sells the Sonnax 2nd gear servo that comes with the longer apply pin (FLT FTW!!!). Seems there'd be no doubt that apply pin forces the 2-4 band to engage to ensure proper grip of rev input drum.