4l60e won't shift!!!!!!!!!!!! ahhhhh
 

I have a 99 trans am with a 4l60/ls1. If I start out from a dead stop and start going it will just red line. If I let the gas out at higher rpm it will shift if I give it some time. Or if I floor it it will just Rev up and red line. Really need help please!!!!!!

Try starting with the shifter in D1, then manually shift to D2, D3 and finally OD to see if that works. If it does, it indicates your forward sprag is shot.

From your description it is most likely the forward sprag or nearly complete loss of line pressure. I assume you have checked the fluid level.
Slight chance of a bad converter, but I don't have the experience on how to test that.

If I manually shift it it does the same thing. Fluid level fine. Did pan flush about 5,000 miles ago

If you want to continue diagnosing it yourself, hook a trans pressure gauge to it.
On Amazon search for "ATD-5550"; its $34 with free shipping if you have Prime.

I suspect the pressure will be very low, below the 60psi idle, 150+ psi in Reverse and 100-200psi accelerating.

Or just get it towed to a local trans shop; in general I recommend a locally owned shop and not a chain. Call an auto repair shop that doesn't do transmissions and ask them whom they would personally go to.

I've heard of this happening due to cracking the pump rotor during the converter installation. The pump works for a while, but then craps out.
Sorry, I don't know if a failed converter would have these symptoms; perhaps someone else does.

I should have asked previously, but confirm whether the problem exists in Reverse too?

I've taken it to 2 trans shops around my area. Everyone is telling g me to replace the whole trans. Not helping me whatsoever. I'm trying to get straight to the problem. That's why I've been trying to diagnostic it myself so if it's something I can easily fix it will save me tons of money. I'm all about saving money :)

Reverse is perfect

Ohhh, I didn't expect that.
That would indicate that the pump is working and the torque converter is OK.
Taking your word that [D1] doesn't work either, we could still have low line pressure (it is greatly boosted in Reverse) or a badly slipping forward clutch.