1995 seville sts with code p086
 

Hello!
This problem has our shop stumped. We have changed the pcm, input speed sensor, vehicle speed sensor, and rebuilt the trans with a new kit twice. We pulled the sun gear and differential gear to count teeth and make sure that the ratio was 3.71:1 and it is. Cannot understand why this code comes back as soon as trans tries to shift from first to second.

PD71 shows 111 and PD76 shows 4.00 (snapshot data) from on-board diagnostics. This is with key on, engine off. Before the trans was rebuilt again the PD71 showed 001 and PD76 showed 1.95 which pointed to the second clutch slipping or dragging. (according to alldata) We could shift the trans manually and did not have a single issue with shifting or check engine lights. ( so the sprag should be ok) Now, we cannot shift manually without the light coming on when shifting from first to second.

I saw this very issue was discussed in 2008 and they never posted what fixed the problem.

Is this an electrical issue? Or did the rebuild center miss something? Anyone have this problem resolved? We have had this trans out 3 times and they cannot find anything wrong with it. HELP! Thank you in advance!

Have you monitored the input speed and VSS data on a scanner? It's possible the sensor daa is either incorrect, or not reaching the PCM properly, due to a wiring issue. These things have a problem with terminals pushing out of the connectors, on both the trans and vehicle harness. I've also seen corrosion form under the rubber/silicon weather-tite seals on the connectors. The terminals will look good from the outside, but if you pull the seal out, the corrosion is obvious.

What was the original complaint before the trans was pulled, and what repairs were done at that time?
Have you checked to verify that the tires are the correct size, or at least the same size left/right on the front?