transmission not shifting from first to second gear normally?

When was the last time the transmission was serviced? When it shifts from first to second is it a hard shift or a very soft shift? What happens when you try to shift it manually from first to second? And the most important thing is, have you checked the fluid level? And if you have used a white paper towel, describe to me the color of the oil or send me a picture.

I had changed the fluid as soon as I got the truck, so it is still good clean red ATF. When it shifts it is just a normal tight shift, no slipping or anything. When I try manually shifting it, it doesn't do anything.

You change the fluid as soon as you got the truck. Was it because the fluid was dirty or was the transmission acting up? When you say a normal tight shift do you mean a hard shift? The transmission shifts firmly? Do you mean when you're manually shifting it from first to second that it doesn't shift ? Or that it shifts and feels like it goes into neutral?

I changed the fluid because it was acting up hoping that fresh fluid would fix it, I even put a new filter in it as well. I meant it is shifts like a normal transmission should. I was manually shifting it from 1st to 2nd and it didn't shift just like if it was in drive and not letting off of the pedal.

It sounds to me like the forward clutch pack is gone that handles third and fourth and then the torque converter locks up for 5th let me do a little bit of study on this and I'll get back to you.

Okay, 3rd and 4th gear shift just fine. It's just first to second that it has issues with I think it is only a 4-speed overdrive transmission should be the 4L60e.

We need to run the codes to see if any are stored, to me it sounds like the 1/2 shift solenoid is getting weak which is common. Please go over this guide and I have included how to change the solenoid out in case code comes up for it.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Check out the images (below). Please let us know what happens.

I had actually put new shift solenoids in it as soon as I got the truck a week ago, I changed all the fluid and changed the filter also. I hooked up my Snap-On scanner and it wasn't throwing any codes, and the live data was showing everything was functioning properly.

Okay, then chances are there is something wrong internally and the transmission will need to be disassembled for inspection. This video will show you step by step what to do on a similar vehicle and instructions in the image below for your truck.

https://youtu.be/3vJAojsrfuU?si=geobbNxiaqFUf_7o

Check out the images (below). Please let us know what happens.