Automatic transmission shifting problem

[Pip]

So what does the TCC solenoid do? Confused how it is supposed to help but good to hear it did.

[Dave1027]

I'm not entirely sure but it seems to control the torque converter specifically it's engagement.

When I compared the new solenoid with the old one, the big difference that I could see was the o-rings on it. The new part's o-rings were definitely fatter and because of that I struggled a little installing it. I don't know if the new part came with upgraded o-rings or the old ones had flattened or shrunk with age but I'm thinking the tighter fitting o-rings will help with sealing. It could be that the cold start issue is due to the o-rings not sealing and once they warm up a bit they seal better and then the torque converter engages more.