I have a 1999 Blazer. I try to put the truck in Reverse and nothing happens. The Check Eng. light is not on. I need Help. Thank you. Jesse:banghead:

FIRST THING (Welcome to the AF)
Have you checked the fluid in the transmission? Is it full or burnt smelling?
Have you had any other problems with the trans before?
How many miles on the truck and when was the last time you serviced the transmission with new fluid and filter?

More than likely, Your sun shell reaction gear is out of your tranmission. How does it drive in forward gears? Does it appear to be shifting right? If not; it's what is called limp mode. I paid 38 dollars (US) for mine. However, it does require you to tear down the transmisson to replace it. You may as well rebuild it while you are in there.
SC

When my reverse went the low/reverse clutch pack was gone.

to test it when going 20mph or so drop it into 1st on the shift lever and see if the truck engine brakes.

If nothing happens or it slows down gently, your low/reverse clutch pack is gone.

Mine was caused by a bad rad allowing coolant into the tranny fluid, you better have that check out as well.

It is this or the sunshell, but with the sunshell you will lose 2nd and overdrive as well.