chevymec

Is there any really loss of performance between the lock-up th350 v/s a non lock-up? I have both but my lock-up has the torque convertor that my new motor should need and I would think since I could lock-up the TC it would help with gas milage a little.

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Pro Built Automatics

If you are going to make a "direct" comparison in terms of perfromance, then the non-lockup is always going to be better because it is "all" torque converter. The clutch "takes away" some of the converter, but the tradeoff is lower heat and better gas mileage.

chevymec

Thanks. When running the lock-up down the track, would I see any benifit of locking up the TC like maybe a better ET? I know that forced induction guys can get some better grunt out of the motor when they do. I will be spraying mine

JamieSweet

That would require a converter built specifically for it, you can get them from Yank, but they're around $900. The lockup doesn't hurt performance except for the few pounds it adds, it's like using a heavier flywheel. When the converter is unlocked, it's still all converter.

Pro Built Automatics

With a normally asperated motor, locking up the torque converter will slow down the vehicle. If the torque converter is mis-matched badly, then you might see a gain with locking up the torque converter. In some supercharged or turbo charged applications, locking up the torque converter might get you a little MPH in the quarter mile. When the torque converter is built correctly and "matched" to the engine/transmission/rear end combination, you should never see a gain in terms of ET and MPH when locking up the torque converter.