Having a transmission shop rebuild your automatic transmission can take from 3 to 7 days from start to finish depending on how busy they are and how many other customers they have ahead of you.
If the transmission shop needs to remove your transmission and replace it back into the vehicle then that can take a bit longer.
Usually rebuilding the transmission itself by a professional transmission rebuild shop with someone who knows what they're doing can take around 1 or 2 days for the rebuild.
Then it can take another day to get the transmission back into the vehicle.
The transmission shop I took my transmission into have rebuilt had the transmission rebuilt in 2 days and had it ready for me.
Sometimes you can even swap your transmission out for another rebuilt transmission from the transmission shop.
I spent $400.00 to have a professional rebuild my automatic transmission and it has been going strong in my truck for 500,000 miles and more.
I keep the transmission fluid changed and change the transmission filter along with the transmission fluid every 30,000 miles.
Changing the transmission fluid will help extend the life of your automatic transmission and if you have any leaks of transmission fluid you should get them repaired to avoid losing transmission fluid which can lead to low transmission fluid level and destroy your transmission.