Driving up in Maryland for 2 years my stang had no problems w/ cold gear clash. 10 second warm up and go. Drive slow and shift slow the first minute or so and good to go. Sounds like you need to flush your transmission oil / do some basic maintenance as well. There is absolutely no reason to warm up your car for 30mins, especially in Dallas (I lived there for 4 years). Besides your car warms up faster when you are driving it, not idling. Very inefficient- Complete waste of gas.
If it were only that easy. Doesn't work that way. It either will not go into gear or it grinds. Doesn't matter how you do it. Fast or slow. There is a huge thread on it in here somewhere. Works fine most of the time after it warms up.
My warmup consists of starting the engine, putting my seatbelt on, setting radio, taking a sip of coffee and then going. About 30-45 seconds of idle and then i'm off. Only thing i do different is drive easily until the oil and other fluids warm up.
Heat comes on much faster if i drive off vs letting it idle for 10 mins. Of course, if i have to clear off snow, i start the car first, then get out and clear the snow off.
Kinda funny when other people think 30* is cold. If it was 30 degrees, i'd break out the bucket and soap and hand wash my car....not joking either!
I'll let mine idle for about 5 minutes for heat. Otherwise I just drive off and shift before I hit 2k. My diesel truck is what I let warm a little. It's a dog when cold
I have a "new" rebuilt tranny and it still does a little bit of clashing on 1-2 shift when cold. Some mornings it does it, some it doesn't. If I shift too slow it clashes, shift too fast it clashes. Usually when I pull out of the drive I'm on a down hill and with the 3.73's I just go straight to third.