When I made my first pass at the track after having my transmission rebuilt, I cut a 1.75 60' and it took off great, but it wouldn't shift into 2nd until I lifted. Datamaster stoped reading mph and the window lit up with a DTC from the transmission. The DTC's I get are:

22-TPS Sensor Low
72-Output Speed Loss

I reset the computer and it ran fine on the next pass.

That was 3 months ago and today I'm in Maryland for the Super Chevy Show doing test and tune. I decided to spray a 50 shot off the line to see if I could lift the wheels (which I did!) and it left hard, cutting a 1.649 60' and wouldn't shift into second, the datamaster started beeping again with the same DTC. I reset the computer and its running great again. Also, no check engine light ever came on.

Why would my speed sensor crap out on a hard launch? What can I do to prevent this? Could anything have gone wrong durin the rebuild that would cause this?

 

Sounds like the dreaded 1-3 shift. How are you launching, what do you stall car to?

 

I usually stall the car to 1500 and it flashes to about 3600. I forgot what the nitrous flashed it to though. I contacted my tuner and he said he has a fix for it, he said it was caused by a bad OBD I reaction to the converter or something like that.

 

If you want to try to stalling only to 1k and launch that worked for me.