I vote 36MM, I just bought it for 20 bucks so i have it in the future.

My blaze likes to hammer into 2nd when cold too, Im not worried about mine, cause my S10 with a 350T did the same thing too, enough to hear a lil peel.

Mine is like shuddering and vibrating, not shifting hard. I wish it would just give me a check engine light code so I could figure out witch sensor to replace.

I'm thinking it could be the IAC, it can cause problems until the car is warmed up and cause it to spudder. Otherwise your tranny is on it's way out, could maybe be the u-joint, I know my u-joint need to be replaced and it shifts hard into second until it's warmed up a bit.

Could I just unplug the IAC valve and see if it still does it tomorrow morning? Or would running it like that cause too many problems?

what tranny is in youre ride 700r, r4 or 4L60e they are all 700r trannys but have significant difrences i cant speculate as to which problem your having or the cure but i may lead you in the right direction 1st locate a good reliable (honest) tranny shop to help with dignosis 2nd learn as much as you can about the tranny itself http://www.novak-adapt.com/knowledge/th700r4.htm ---- http://www.novak-adapt.com/knowledge/4l60e.htm --- good luck who knows you maybe rebuilding your own soon

mine has the 4L60E tranny.

A slow or stuttering 1-2 shift could be caused by a problem with the 1-2 accumulator piston. It is easily accessible with a pan drop. The problem could either be a cracked piston (unlikely) or the piston may be getting cocked in the bore and sticking. The sticking could occur after things cool down and then the first shift knocks it loose and it works from there. Something to check.