overdrive issues

[nvmyvettes]

I have done several things tring to repair my 95 Rora.I replaced shift solenoids w/bracket.I got 1st,2nd and 3rd gears after replacing them, instead of just 1st and 2nd.Now I have no o/d.The Mechanic at a local dealership says any sensor thats bad on tranny, or on the motor that ties into tranny will cause you not to have o/d.As long as Im in 3rd and dont shift to o/d I get no codes.However if I shift to o/d the tranny goes back to 2nd(limp mode)and I get codes.(IAT sensor,
Cruise engaged not in drive, Brake booster sensor,no such thing by the way)His suggestion was to start replacing sensors.I dont want to start replacing $$$$.I know one thing wrong can cause several things to read bad.
The thing that puzzles me is in 3rd gear no codes.It seems to me if a sensor was bad it would be bad in all gears.Can a sensor be bad and only show up as a code in o/d?

[maxwedge]

A full scan with a trans capable scanner done by a trans tech, can confirm tcc lock up solenoid activation and slippage errors, any thing else will lead to guess work.

[baron1701]

I Had A Similar Problem When I Did A Bunch Of Overhauls To My Intake, Fpr, And Egr. I Installed A Faulty Fpr And Lost Overdrive. An Fpr Or An Egr Will Do A Similar Thing. In Fact Its Surprisingly True That Any Number Of Sensors Could Kill Your Overdrive.

[nvmyvettes]

Your right Baron! I can tell you been through it.When you had your problem did the SES light come on? And if so what were your codes? And if you had it scanned, what did you use as a scanner? I went to Advance and they used the Actron Superscanner.It doesnt work very well on the 95 Rora.Gives false codes.
Thanks in advance for any insight you can give.