Transmission issue when slammed on brake?

2005 DC new owner here with 177k. Flushed transmission about 10,000 miles ago because of that reason. When I slammed brake to full stop or less than 15 mph, my transmission doesn’t downshift until I press gas. It doesn’t downshift smoothly when it happened. It’s still doing that when slammed on brakes. It downshifted smoothly if I didn’t brake hard. Low transmission fluid or I need new transmission?

 

Mine will often try to start in 2nd gear with soft starts. Probably programmed that way for efficiency / MPGs? So maybe your abrupt starts and stops are highlighting that?

 

Possibly low. Are you sure you put in the exact amount you took out?

You know the proper procedure to check fluid level on the sealed transmission that comes in the '05-'06? If yes, have you checked it?

 

Sounds like you're low on fluid and slamming on the brakes sloshs all the fluid forward away from the pickup. How does it accelerate? Mine would rev a little then slam into gear when I was low.

 

I've been researching this off and on for a bit. I get this too, but seems to be better after my initial drain and fill. It happens less often and with less severity that I've nearly forgotten about it.

As suggested, I would definitely check transmission fluid level. And top off if needed. Maybe even try and skew towards having the fluid level at the higher end of things. Meaning pulling the plug that sets the fluid level at the lowest temp of the check range. Or maybe even slightly below that temp.

It's definitely helpful to have something that can read transmission fluid temp. As that is much easier than doing the song and dance to get the transmission temp light to flash at you correctly. Most OBDII scanners that read live data should be able to show this to you.
If you have a ScanGauge II or III, I can give you the X-Gauge commands for transmission temp, converter temp, converter lock status, and gear position. Or PIDs for Torque Pro for the transmission and converter temp.

I also have a ScanGauge II for sale on the forum marketplace for a decent price. It is pre-programmed with transmission temp, converter temp, converter lock status, and gear position for the 5 speed 1st gens.

 

You can also just use a thermal gun if you have one, shoot the pan. I usually prefer posting Faye Hadley's video on sealed transmissions in our truck, but Tim the Toolman has one also. This, I feel, really breaks it down more-simply.

https://www.youtube.com/watch?v=ej_6BZpK3gg​