Did a tranny swap and I'm thinking this issue has something to do with the driveshafts- mainly the u-joints. As I was backing up to test reverse I spun wheel left and the blazer stopped moving in reverse with the wheel turned - same thing in both directions.

My torque wrench is old so maybe the u-joint caps are on too tight? I'm too cautious to take the blazer on the freeway yet so I don't know if there is vibrational issues at higher speeds yet.

What could be causing this?

 

If it is in 4wd, it will do this. Other than that, u-joint cap tightness will have nothing to do with steering bind.