(automatic)

Shifting from first to second - HARD (seriously... like, give you a migrane hard).

Second to third - SLOW (2 seconds to fully shift).

Third to OD - 1 second

The car is still new to me, so maybe a shift kit was installed to make it do this?

Or does anyone notice something specific that might be a sign to it going out?

 

I don't think this is a shift kit issue. I have had shift kits before and still do. They shift hard all the time. That is unless someone screwed up the install or has it set up deliberately but I can't think why they would do that.

Have you checked the fluid and see if it is fresh or burnt? The best case is that you get used fluid. Burnt is bad and new is not good either. New could mean that he has smelt it and determined it is bad or has dropped the pan and found metal chips in it. In that case, the seller would change the fluid and filter and close it up then put it up for sale.

When the fluids are too fresh, I worry that someone is hiding something.

 

Fluid is brand new actually and looks fine.
I just wonder why it would shift good, except for the 2 to 3?
Im by no means a tranny expert.

If it does need to be rebuilt, do you have any suggestions (like kits I should buy, or just buy a whole new one?)

 

Why is the fluid new? If I am going to sell my car, would I bother to flush the tranny if I didn't have to?

Sounds like a lot of slippage in the 2 - 3 shift.

Talk to www.rosslertrans.com for a rebuild. The come recommended by Lingenfelter Perf Engr when I asked them. They cost a little more than a GM shop rebuild because I wanted a different Torque Converter. Behind my 383, the GM rebuild lasted 6 months when I babyed it. Rossler rebuilt it and it lasted 3.5 years with me beating on it. You do the math.

 

When the Trans-Go is installed correctly, you can have nice smooth part throttle shifts, with the shifts getting firmer with more throttle. Sounds like you have the B&M valve body kit?