Running a 700-R4 in overdrive with no lockup is a big heat generator, and can cause early transmission failure. That's why the lockup is there - other than to increase mileage. This is especially important with high HP engines and increased stall converters. Check with whoever built/supplied your trans about what to do.

Some trans suppliers won't warranty a performance R4 unless there's both a radiator tank cooler and an auxiliary cooler - although most people seem to get buy with just the auxiliary cooler.

Seriously, check it out.