Been having harsh down shifts when coming to a complete stop. Feels like a quick jerk just as the wheels quit turning. Problem goes away once the coolant temp gets to 190 degrees. Anybody have any ideas what is wrong?

Check the motor and trans mounts first. After that I would guess it'* a sticking shift accumulator. This is a easy fix if your handy with a wrench.

as dan said its probable that its your trans mount, check your fluids as well

How would a broken mount affect the down shift? Plus why would I have no problems after the engine reaches normal operating temp?

The motor and trans can move freely. It'* more likely it'* the shift accumulator but checking the mounts is easy.

Bad pressure control solinoid in the trans??

I have also noticed that I have no harsh down shift if I have the transmission in "3" and not "D".
Thinking problem may be in the overdrive part of the transmission. Possibly staying locked up till right before the car comes to a stop?

Hmmm

The harshness is only when the trans is cold. It'* only downshifts and not upshifts.

Thinking about how the motor pulls/pushes in your years mounts..hmmmm

I want to look at an ATSG (trans) book that I have to see what it suggests. I'm thinking something with the seals is not happy until it heats up. But I'd expect upshifts to be having issues as well.

As for the TCC lockup not disengaging. What MPH are you getting up to when this happens. TCC will lock and unlock in 3rd as well as Drive. If you are getting over 40-45, then lockup should be happening in either gear.

All upshifts seem to be ok. The key here may be what goes on differently in "3" and "D" that would affect downshifts from 2nd to 1st? The gearheads at OReilly think that the torque converter is staying locked until the wheels almost come to a stop. Not being real familiar with how and when it locks and unlocks I am not sure what to believe. It does seem to me that I read somewhere that the torque converter only locks up in "D". Thinking I need to do some more learning.

I have a tuner and have built a transmission. In doing both of these, I've asked many questions and learned quite a bit from transmission guys, tuners etc etc.

Our transmissions will and can lock when the shifter is in the 3rd gear gate (no matter how it'* called 3 or D with 4th being OD). The tables in the tuner specify that the trans be in third gear and above a certain MPH with certain throttle percentages. This means that TCC won't lock when you are under say 70%+ throttle. I have also done many tests as I've had my share of issues... and been able to get lockup with the selector in 3rd. If the TCC is staying locked you should see a code for it. I think it'* P0742 TCC stuck on. Not sure I'd give the generalists at O'Reilly'* too much, they may be great guys..but they aren't quite trans specialists.

To my knowledge I have never seen any programming regarding the downshifting. Which then leads us toward a seal or maybe the trans not shifting down out of 4th properly.

4th gear has only two friction plates where most other gears have around 7-10ish. I forget the actual number. This can heat up the 4th clutches and cone them (shape wise) due to heat. It could also potentially adhere them together.