My 1997 Blazer transmission died so I went to a junk yard and got another one. Replaced it although it was a pain it went really well. But now even full of fluid and all connectors reconnected the transmission will not engage. It shifts into gear no problem but nothing happens at all. No reverse no drive no matter what gear you use. I have heard something like a (SPS Shift sensor) will cause this but where is it and how do I check it. the old transmission was just slipping in all gears but it ran. Please help if you can...