I HAVE A 1990 SILVERADO WITH AN AUTO TRANSMISSION, NOT SURE WHAT MODEL BUT ITS GOT OVERDRIVE.THE PROBLEM IS WHEN IT SHIFTS FROM 2ND TO 3RD I HAVE NO 3RD ITS LIKE ITS IN NEUTRAL. I HAVE TO PUT IT IN 2ND TO DRIVE IT.IS THERE A VALVE OR SENSOR OR SWITCH THAT MIGHT BE BAD OR IS THE TRANNY TOAST

 

Sounds like the tranny is just going out man. Sorry, I know that ain't cheap. I was quoted around $1,500-$1,800 to rebuild the tranny in my 95 Z28 when I had it so I imagine your looking at about the same price.

 

It's a 700r4 trans. If its 2wd just goto a u pull it wrecking yard and you can get one out of an astro van for less then 100 bucks if it's 4wd then get one out of a s10 blazer, 700r4's are exactly the same for a 4.3V6 ora V8

 

If you do that make sure you get a late model 700R4. I've been told by a tech who used to work on GM trannies that the earlier 700R4's were prone to failure.

 

Don't those have seperate solenoids for 1-2 and 3-4? If so then maybe a solenoid is out or unhooked.