I have an 89 GTA Trans Am w5.7L TPI motor.  I'm at a loss and am in need of
some help and guidance.  The car according to the snap-on scanner I used is
running in "LIMP HOME MODE".  The first problem is there are no codes in
the computer.  I've done the tap test on the ECM and MAF.  ...

I just changed the gear oil in both 95 Z28s. One is 3.23 and the other 2.73.
With both wheels off the ground and rotating one tire, I noticed that the
2.73 acted very much like a non-posi rear end. The other wheel rotated in
the opposite direction and did not turn the drive shaft.