I need to make a decision on my freshly rebuilt trans...
 

I had my transmission rebuilt a few months ago...

After about 4 weeks 2nd gear has been doing this...

1) 1st to 2nd upshift, crunchy as eff but no grinding. All other gears seem fine and the trans seems nice and tight.

2) down shift from 3rd to 2nd it's smooth as butter.

The only thing that didn't get replaced was the transmission case itself and the countershaft.

Take it back to them and throw a fuss or what? I have a 1yr or 12,000 mile warranty.

your upshift description needs a little work.

Like a worn out synchro. Up shifting into second is like a "cluh clunk". All the other gears are fine and downshifting into second is like butter.

I need to make a decision on my freshly rebuilt trans...
 

Sounds like if you have the time and willingness to pull the trans, you've got your answer. Just call your rebuilder first and discuss the issue.

I would take it back, you paid a company to rebuild your trans. if something isn't up to par within the specified warranty period than it is their responsibility to fix it

bring the whole car there and see what they think, not just a transmission in the back of your truck

i would take it back if you think it is getting progressively worse. they probably forgot the thrust shim for the front mainshaft bearing which sets the thrust play for the 1/2 syncros and is easily overlooked.

yeah do this