[Cliff R]

"Many builders used to convert the trans to non-lockup because the converter technology wasn't there to support the power, and because they couldn't get the trans to live with the converter locking."

This is NOT the case here, never has been. The TCC is retained in all cases if the vehicle came with an OD trans to start with, and all of the associated parts to effectively operate the TCC were still in place and operational.

Having owned and driven several vehicles retrofitted with OD transmissions, my opinion. If the drivetrain components are well chosen, ie, effective gear ratio for the vehicle weight, power, etc, using a TCC becomes an option. This also assumes that you are hiring a good company to build your converter, and it provides efficient characteristics, decent flash stall, combined with effecient light/part throttle and very well coupled above the stall speed.

We never allow TCC operation before OD, if/when it is used in retrofits. This is easily accomplished by using a Normally Open 4th gear pressure switch as a ground, and routing the voltage thru a vacuum switch, then the TCC solenoid. The vacuum switch hooked to ported vacuum will provide near perfect TCC function, as it will unlock when coasting, and at any heavy/full throttle operation. Basically, it will only lock-up at light part throttle in OD.

As good as this scenario sounds, when actually driving the vehicle, it is beneficial in many driving situations to have a slight amount of torque multiplication in OD. This avoids having to downshift, and/or unlock the TCC, lug the engine, etc. After logging many thousands of miles with them hooked up each way on several vehicles, my preference is not to use a TCC. While I'm at this, the WORST condition for the TCC, is to be moving along in traffic on secondary roads at 40-60 mph, on and off the throttle, speeding up and slowing down, the TCC will be in-out, in-out a zillion times and drive you absolutely NUTS. If direct wired it will lug the engine to death. This is when most drivers select the toggle switch mode and take it out until they get on the highway and back to steady speeds.

I just got a call recently, from a friend mentioned above who chose the TCC route, and isn't liking it much. He simply finds too many driving situations where the trans either has to come out of OD, or the TCC switched off to avoid "lugging" the engine. His unit, nearly as I can remember is set-up with direct wiring to the 4th gear pressure switch with a toggle switch to unlock in manually if/when needed.

The last arguement for using the TCC is to avoid transmission overheating, which is utter non-sense, and it goes right back to correctly selecting your OD and other drivetrain components in the first place. We ran our Impala SS over 35,000 without any cooler other than the one in the radiator. We simply used 3.31 gears, and a custom converter designed for this purpose. It was actually "tighter" than the custom L/U converter it replaced (before the TCC came on), and fuel milage, or difference of was barely noticable between the two converters. Just some additional information to help folks choose which way to set these transmissions up for older vehicles......Cliff