My 95 STS with only 117,000 km(about 80,000 miles?) started to 'jerk' between shifts(especially between 1st/2nd)....Eventually the check engine light came on and I took the car in for service. I talked with my mechanic today; he said the only code it is showing is C 40 which has something to do with the transmission. Thats all he could tell me until he spends some more time with it, does anyone anything further about this issue?

Thanks

No such thing as a C40 code.
http://myweb.accessus.net/~090/dtcobd1.html

interesting......I probably just heard him wrong, but I'll be sure to call and confirm the code tomorrow.
Thanks

Sounds like another P056 code, transmission input speed sensor.