Symptom is this - transmission works great during warm weather but in cold weather (below 60 deg.) when the transmission is cold (1st trip of the day) after leaving my house and driving about a 1/2 mile it hesitates in shifting from 2nd to 3rd (1st shift pattern) almost as if it is flairing but I don't think it is because it doesn't shift between gears or have a fluctuation in r.p.m.s. This is not the delayed upshift for catalytic conv. and usually occurs anywhere from 1/2 to 2 miles from start up. It is almost as if it is pump related (it seems as if it wants to shift but can't) after a second or two it will shift up to 3rd. Does not do this any other time and rest of the time the transmission works great.
This is a used transmission that was installed two years ago. At the time of install it had approx. 80,000 miles on it. I have installed a K1 kit (no difference), a new modulator valve (and have checked according to specs.) and changed the fluid and filter at least twice in about 10,000 miles (used Mobil 1, of course). I have no idea about previous maintenance of this transmission or type of fluid used but it was clean when delivered but not like a recent change. Any ideas would be appreciated. This one has me stumped. Thanks.