Transmission Thermal Bypass

[440scout]

By far, the biggest producer of heat in an automatic transmission is the torque converter. It's the liquid coupling between the engine and transmission that allows the engine to run while in gear with the vehicle stopped. The transmission fluid gets beat to death inside the torque converter. So periodically changing transmission fluid can greatly extend the life of the trans.

[GlasNav]

Thermal Bypass, what happened to secondary transmission coolers? It was a popular thing years ago, installed with a bypass for winter months.

[wiredgeorge]

Originally Posted by GlasNav

Thermal Bypass, what happened to secondary transmission coolers? It was a popular thing years ago, installed with a bypass for winter months.

For winter months, folks found that a large piece of cardboard covering a radiator did work just as well. Back in the last century, when I rode air cooled bikes and installed an oil cooler for the hot Texas days, I found in the winter that the oil never got up to operating temps so installed a bypass that allowed the oil to warm.

[rhagfo]

Originally Posted by 440scout

By far, the biggest producer of heat in an automatic transmission is the torque converter. It's the liquid coupling between the engine and transmission that allows the engine to run while in gear with the vehicle stopped. The transmission fluid gets beat to death inside the torque converter. So periodically changing transmission fluid can greatly extend the life of the trans.

Now days with the lockup torque once locked up should not produce to much extra heat.

[Campbell701]

With locked up clutch in torque converter you less torque capacity and potential for more NVH in driveline - overall less pulling capacity.

[Campbell701]

As 440 has already stated the torque converter is the big source for increase heat — but it also is a multipler for increase in torque to transmission.

[rhagfo]

Originally Posted by Campbell701

With locked up clutch in torque converter you less torque capacity and potential for more NVH in driveline - overall less pulling capacity.

Well having driven a 5.9 CDT 5 speed manual for over eight years, never had an issue just being in the correct gear and stepping on the throttle.
Now have an 6.7 CDT and expect once the Aisin shifts to the correct gear I expect the torque converter to lockup and pull.

Maybe in the days of two speed Powerglides one needed the fluid connection to compensate, but not with. 6 sped or 10 speed automatic.

[440scout]

Originally Posted by rhagfo

Well having driven a 5.9 CDT 5 speed manual for over eight years, never had an issue just being in the correct gear and stepping on the throttle.
Now have an 6.7 CDT and expect once the Aisin shifts to the correct gear I expect the torque converter to lockup and pull.


Maybe in the days of two speed Powerglides one needed the fluid connection to compensate, but not with. 6 sped or 10 speed automatic.

Yes, cooler until the torque converter unlocks while pulling a heavy load up a long steep ungrade like climbing I-70 to cross the Rockies. Although the ambient temp will drop as you gain altitude and helps with the cooling you can still expect a big jump in the trans temperature.

[gearhead]

Dang, I don’t think my Aisin has been anywhere near 180F, usually 165F.