Rumor has it that when the Torque Converter Clutch locks up, fluid flow to the cooler is reduced on purpose. I know that when the transmission temp goes above 260', the ECM will begin locking up the TCC in 2nd and 3rd, in addition to OD 4th! I experience it every summer. I end up having to disconnect the TCC so I can drive without the motor lugging from the ECM holding the TCC in all the time. It shifts a lot smoother, but my gas mileage goes to crap, too!

If the cooling restriction is true, is there some way to remove the restrictor so the tranny can get some cooling even when the TCC is locked and in OD?

 

How does the computer even know what the tranny temp is? There is no fluid temp sensor. These trannies where phased out before fully computerized transmissions were produced. The only computer controls in the tranny are the 4th gear pressure switch and the tcc solenoid. The 4th gear pressure switch is there so the computer knows when the tranny is in 4th gear because that is the only gear it will lockup in. How does it know when to lock up in 2&3 but not first? As far as I know fluid flow to the cooler is not reduced when the convertor is locked up. I see no intrinsic advantage to that. The only change between lockup and nonlockup is the tcc solenoid activates and fluid flow is redirected through the convertor not cooler. The tcc solenoid does not move any valves that I know of. how do you know when the tranny temp is over 260'? That is way high for tranny fluid. Do you have any varnish in the fluid? I think your problem lies else where.

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82 z28 350cid, vortec heads, comp 262h cam, Holley 600cfm carb, 2in twice pipes, MSD ignition, turbo 350 trans, 3.73 posi, manly b&m megashifter

 

In some transmissions there is a temperature activated switch which applies power to the TCC solenoid in any gear above first when the temperature is high.

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1984 Camaro Z28 Astral Silver w/ 2 1/2" cowl induction hood
Engine: Decked 383 cid 4 bolt w/ oil cooler, 9.6:1 compression, ARP fasteners, 600 cfm Performer carburetor, Torker II intake, Performer RPM Heads, XE268H cam, Magnum roller tip rockers, MSD6AL ignition, Blaster2 coil, recurved HEI distributor
Exhaust: Terminator headers, Custom 3" TIG welded stainless exhaust, Twister muffler
Transmission: 4L60 w/ Corvette servo, .500 boost valve, TransGo 7-CS clutch springs, 700 PKH pump rings, 700-2 reprogramming kit, Borg-Warner High-Energy frictions & bands, 2400 RPM lockup torque converter
Drivetrain: 2.73:1 limited-slip Dana 44 w/ disc brakes
Tires: Front P225/50VR15 Rear P265/50VR15 Eagles