I was wondering if an external automotive oil filter would be beneficial, the kind of setup used to relocate an engine oil filter? Also the factory cooler is tiny, I don't tow anything but may add one to the factory cooler. I have read to use mopar trans fluid only in these, the dipstick says dextron II, any thoughts on this. And what about the big heat exchanger under the exhaust manifold, how efficient is it? I think I read that there is not a drain plug in the converter, correct? Any other ideas on keeping the 518 alive. Thanks

 

You're on the right track with these questions. I'll start the replies.

If you keep the 518 fluid temperature at or near the operating temp it likes (~140-170) you'll go a long way to keeping it happy. How to know the temp? Put in a gage so you know what it's doing. Some like to put the sensor for the gage right at the output of the trans, where you will see the highest temperature. Others like to put it in the pan so they can see essentially what's going into the trans. Mine's in the pan, but I'm adding one to the output; a switch allows me to look at either one.

The heat exchanger under the manifold works two ways. If you start out in the morning, engine coolant temp rises fairly soon and will help trans fluid temp to get up to operating temp. The engine coolant stays at about 170 due to the thermostat, so if the trans fluid got hotter, that heat will be passed back to the engine for dissipation at the radiator.

The problem in the paragraph above is that trans fluid temps can get above 170 real quick when you're towing or sitting still on a hot day; faster than the exchanger can get rid of thru the coolant.

An add-on cooler which has a temp-controlled fan to force air through it is the common solution. Dodge even offered an option to our trucks to put one in, under the bed on the driver's side; but these are long gone from the parts system. I installed one of these (I tow a 5er) and it works fine.

Dexron on the dipstick should not have been there. DC later came out with a blurb that it should be used only in emergencies and that the correct fluid to use is one that satisfies Chrysler spec 7176. Advance Auto sells an ATF +3 that does this. I use it.

DBF

 

You can get a fan cooled auxilliary cooler like DBF described from Summit, Jeg's, etc.