This is a 1989 Pontiac Trans Am. I swaped a 6.0 LS in to it with a T5 transmission. The speedometer only rteads when that the cluthc is fully pressed to the floor. Electronic spedomerter, sensor wired directly to the buffer box. I had to use a LS belhousing and the transmision is no longer on the 20 degree angle from factory, it sits srtaight on the bel housing. I used a mcleod hydralic clutch set up if that make a diffrence. How is this possible?

 

My guess is that you should ckeck the position of the drive gear for the speedometer, thinking that it is not centered over the driven gear for the VSS in the tailshaft housing. If could have slipped forward a bit if the gear clip failed. You might also discover some end play in the input housing.