Hey guys I had just recently got a transmission that was rebuilt. Got it for my 2000 Silverado 1500 with a 4.3. Installed it and also put on a new neutral safety switch. Anyways when I put the truck in drive, it shifts to 1 and 2 really quick. And what I thought was Third gear I guess really isn’t. When I hook up my HP Tuners, I’m able to command 1st and 2nd gear but when I command third it acts like it’s in Neutral. I unplugged the main harness to see if it would go into limp mode because I remember reading that when it goes into limp mode 3rd gear is what you’re in. So When I did that the truck does move sluggish in what I believe is third gear unless it’s actually only moving in 2nd. I’m just wanting to make sure this isn’t an electrical issue. I am not getting any codes.

 

Doesn't seem to be electrical. It would help to know what the line pressure is when shifting to 3rd gear but sounds like something is wrong with the 3rd clutch circuit.