I know they didn't have the 700r4.Could it be it was the TH350C with lockup toqure converter?If so does that give you an overdrive?

An 81 does indeed have a Turbo 350C. It does not have an overdrive.

350C(lock-up)....simply put, the torque convertor has a clutch inside it. At a specific vehicle speed, the clutch applies, and the convertor is then "locked". Similar to a standard trans, the input of the trans is connected solidly to the flywheel/crank, providing a direct drive, with no torque multiplication from the convertor. It does not give you another gear(O/D), but it does give a slight improvement in fuel milage, due to the convertor not slipping anymore. Adams' Apple38766.8380671296

Thanks Adams Apple.Thats kinda what I figured.My friend just bought one and is trying to sort it out

Zgator,

To put it complex, there is a normally open (NO) pressure switch in the trans that closes when in top gear (maybe 2nd too) wired in series with a NO vacuum switch held closed when vacuum exceeds 6 - 8" hg (cruising vac) then in series with a NO limit switch held closed when the brake pedal is not depressed. At high vacuum cruising with the brakes off they all energize a lockup converter solenoid to give a rigid connection between the engine and trans. When you accelerate, the vacuum decreases opening the vacuum switch unlocking the converter which feels sorta like a mini passing gear with the slip and torque multiplication of the converter. The brake switch keeps the engine from stalling when you slam on the brakes locking up the wheels.

No overdrive like a 700R4, but nonetheless a cool setup. I think it was exclusive to the '81 model year 'cause they went to the TH 700R4 4 speed OD trans in '82.

DaveAutom8r38772.8795833333