Revs high going into 2nd, then slips
 

97' Blazer, 1st gear is great, then revs high to go into second, while in second (15-25mph or so) it feels like it is slipping in and out of gear. Once I get it over 30mph, it eventually shifts into 3rd and so on and drives like there is no problem.

Ok, now i have never heard of this before, but the guy at Autozone said there might be a chance its the cat converter being plugged. I know, Im not a certified tech, but Im also not that dumb, and Ive never heard of that before.

Any info would be great. Thanks

GO ARMY