I have a 02' Trans Am WS6, automatic transmission, the car is almost completely stock, (Just a different muffler.) And after alittle fun after a long day, something, somewhere decided to give out on me.

The car starts up like normal, and drive forward and everything, but the issue is when it shifts. The car will wind up all the way to about 5k before shifting to second. and when it shifts to second, it feels and sounds like its actually going into third. Now, If I use the gear selectors on the actual shift, the "1 2 3 D", It starts in first fine, but when you go to second it doesn't drop the RPM like it should, but going to third it does. does fine going from third to drive as well. Going backwards, it's the same deal, third to second, the RPM goes up as normal, but it stays the same when you go to first.

Research says it's the 2-4 Servo, or the Sunshell/band has worn out.

My O2 sensor was replace before all of this happened, but I cant remember for certain if it was doing this after it got replace, and I was told the O2 sensors, the MAF sensor, and the transmission were all on the same fuse.
What fuse is this exactly? and how would I test it?

 

2nd gear is gone or its unable to shift into second. Take it to a trans shop and have them look at it.

4L60Es are notorious for 2nd gear issues.

 

This sounds like the band has worn out.
You are correct that it could also be a servo problem, but after many miles it is usually a worn band. As the band wears, usually 2nd gear is lost first and a bit later 4th is lost as well.

Here are some similar threads about not 2nd (and/or 4th gear):
https://ls1tech.com/forums/automatic...t-trouble.html
https://ls1tech.com/forums/automatic...-my-4l60e.html

For people that are mechanically inclined and can do a bit of welding, I have suggested lengthening the servo pin to get maybe another 5K-10K out of the trans:


https://ls1tech.com/forums/automatic...t-trouble.html
https://ls1tech.com/forums/automatic...-gear-all.html
https://ls1tech.com/forums/automatic...ckup-help.html

 

So I am going to be converting to an LS powerplant soon. I need to get a 4L60E as well, I have seen rebuilt ones go anywhere from 600-900 bucks. Is this something that would normally get replaced when a tranny is rebuilt?

 

OP see this thread.

https://ls1tech.com/forums/automatic...cond-only.html

 

At $600 the bare minimum is going to get replaced and then with the cheapest parts, but I suspect the frictions and band will always be replaced.
When you consider the time/cost/hassle of just removing/installing the trans, you don't want to go too cheap.
I suspect builders selling a <$600 rebuilt trans are mostly selling to people who's car is on it last legs and if the trans lasts even two years it will outlast the rest of the car/engine.

Even at $900 I would talk to people who have used that builder to see if the trans held up in any kind of performance application. I think that sponsor PerformaBuilt sells a Level-1 for not much more than that.