4L80e Transgo Kit, now DTC 87

[78Chev]

Just put a transgo shift kit in 4L80e (95 GMC 2500 6.5). Fixed my 1-2 shift problem but now I get DTC 87 (high ratio) right after it shifts into 3rd at highway speeds (never shifts into 4th) and then goes into limp mode. I've had it apart again and everything seems fine. Didn't mess with the input or output speed sensors. Replaced 1-2 and 2-3 solenoids and seals on servos and accumulators and made sure nothing was sticking. Using GMTDScantech I can shift into any gear and turn on/off all solenoids including TCC. Anybody have any ideas?
Randy

[More Power]

It's detecting slippage.... I'd verify that the input/output speed sensor connectors weren't mistakenly swapped (if that's possible).

Make sure the ATF level is where it needs to be.

Jim