Engine/Transmission (1994 - 1998) Transmission circulation question

[kwoodson]

Just installed a trans. temp gauge on my 97 Dodge because when pulling on long steep grades, engine would heat considerably. I have discovered that the heat was from trans. I have also discovered that the trans. will heat up and hold a high temp. even after I back out of throttle, but as soon as I lock the torque convertor, the trans. temp. will immediately drop, as if when the TC locks fluid is immediately sent through cooler. I understand that until the TC locks it will build heat due to fluid slippage. Can anyone explain the fluid circulation, This is a 47 RE. Any help will be greatly appreciated.

 

[cerberusiam]

Where is the temp probe?



When the TC locks a shuttle valve will route full line pressure thru the cooler. Doesn't mean all the fluid goes there but the bulk of the fluid is being routed to the coolers.



In fluid coupling only about 1/4 of the fluid is routed to the cooler. The bulk of the fluid is circulated thru the TCC for the fluid coupling then dumped directly to the sump to keep enough fluid available. In lockup mode this isn't need becuase fluid doesn't circulate as much to just keep the lockup piston applied.





As you noticed, engine temp climbs when the trans is in fluid coupling. This is by design as the cooling systems are oversized and can handle a lot more heat than the engine normally generates. Fluid-to-fluid coolers are much more efficient and removing heat so the first stop fluid in this design is the cooler under the turbo. It uses the engine for a heat sink and not only cools but warms the fluid. The front air-fluid cooler is to take the rest of the heat out of the system.



On the 3rd gens there is a thermostat in the fornt cooler that will route fluid back to the trans if the temp does not exceed 140 degrees. Not sure if the 2nd gens have this integrated or not. The operating temp on ATF+4 is 140-240 degrees so a lot of things are done to keep it in that range.



I am pretty sure the 2nd gens have a check valve in the cooler output line that helps with drain back but are problematic when it comes to cooler flow. There are a restricion and trash trap and will impeded good cooling. Best results are obtained by removing it and fixing the fluid flow in park.

 

[kwoodson]

Thanks for the info, how would one go about fixing the fluid flow in park? I have already removed the check valve, again thanks for the info!

 

[kwoodson]

The temp sensor is located in the pressure line feeding the heat exchanger or the water to oil cooler

 

[cerberusiam]

A shift kit will do it, or, Sonnax makes a replacement manual valve that will do the same thing if you don't want to go the route of shift kit.

 

[PhillipFleming]

A sonnax "sure cure" kit is the way to go! while yer in ther mod the plate for better lock up apply. Grind the slot to . 500 (1/2 inch) then drill 1 . 080 holr right above it in the valve body by the 4th spooled switch valve. You wont belave the diffracne it makes in TCC apply.