I've been logging data from my '95 z28 using Datamaster ever since I installed the new transmission & 3000rpm Edge converter.

I noticed that occasionally it will show up a negative number in the section for "Slip RPM" under Transmission Data.

Example: Like when I tap the brake so the lock-up converter disengages, the rpm's drop to 1000-1200rpm and -500 to -700 slip rpm is listed.

Also, while crusing in 3rd gear it'll show up with -300rpm sliping.

How can my transmission have negative slippage?

 

Wouldn't that be when you're decelerating, and the engine speed slows down below the no-slip speed?

Would an un-programmed gear swap affect this, maybe? The slip RPM # is just a calculated value.

 

I get a lot of negative slippage while driving too, not only while accelerating, I was just curious what it meant. I had it programmed after the gear swap not sure what all was touched by him though.

 

Well, you should only see negative slip when you're decelerating, AFAIK. Mind you, my car's a 6-spd, so I don't see any slip. Actually, all the trans info is disabled in Datamaster when you use it with the M6.