DTC 84 too few 24x reference pulses

[tmesis]

A little history: I have a 95 Aurora with 90,000 miles. It has a new transmission and I have owned it for about 2 months. 3 weeks after I got it, (transmission was installed right before I got it), it started shifting hard and the check engine light came on. I have a code reader, so I hooked it up and got "84 - IC Too Few 24x Reference Pulses"

The light does not come on all the time as with most people with the hard shift problem. If I clear the code it normally goes for 2 - 3 days for the light to come back on. When the light is off the car runs great. I have never seen anyone in the forums that has had this code. I thought it was the speed sensor that everyone talks about but it is not throwing that code....

From what I can tell, 24x is a Crank sensor. Could that be causing this problem? Logic tells me that if the tranny is going to high pressure when the light comes on that it is a tranny problem.

Any thoughts?

Thanks