Happy belated Turkey Day all! I just installed my 26,000 gvw Perma-Cool trans cooler, in front of the ac condensor on my 93 W250. I am now getting ready to plumb the lines. Looking down at the engine in front of the truck, specifically the air-to-oil cooler - is the top line going to the air-to-oil cooler the return line to the transmission, and the bottom line the pressure line?
I know I can remove both air-to-oil cooler lines, put plastic zip bags on each line, start the rig for a few seconds - and find out which line is the pressure line. Just thought it might be easier to ask first The trans is an a518 if that matters?
Also, are the air-to-oil cooler lines left hand thread? I was working counter clock wise with a 19mm combination wrench, and the line fittings on the air-to-oil cooler will hardly budge.

 

bumpitty bump

 

Dunno about the flow direction. "Most likely" top is pressure and bottom is return. There was thread here just a few days ago (I think it was yours about the filter Billy!) where somebody who knew said the front line on the trans is pressure, IIRC. If you trace it from there that should answer the question. FWIW, I seriously doubt you're gonna see lefty threads on there, but again, dunno. Got a Getrag. Seems to be leaking. Veeery slowly. Probably normal.

 

Normally the line coming out of the front of the transmission (closest to the bellhousing) will be the cooler output, or pressure line. This is the hot oil coming from the torque converter. The rear line will be the cooler return line, and in many cases it is also the tail section lube as well.

If the lines are stacked (which I don't believe Dodge ever had on these series of transmissions) the cooler out is usually the top and the cooler in is usually the bottom line.

You will have to trace the lines from the transmission forward to find out which one does what out front.

 

Thanks all for the info! I pulled both lines going to the air-to-oil cooler saturday. So, I found my pressure line (closest line to the oil pan, looking down on the drivers side of rig. Line in front near the fan is the return.) For some reason my 93 fsm has these lines reversed (maybe for a gasser?). I initially went by the fsm info, then figured I better pull the trans lines to be sure. Glad I did, as I had the trans cooler plumbed into the pressure line. I also changed out the lines for new Gate's 1/2" lines, since they looked to be of 93 factory vintage.
I also wanted to flush out the factory air-to-oil cooler, before I plumbed in the new trans cooler. I tried to remove the factory lines screwed into the cooler, at the front of the truck. I couldn't get them budge, even soaked with PB Blast So, I removed the rubber lines on the back of the air-to-oil cooler, and flushed the cooler from there. Got alot of crud out! This might help anyone else trying to do the same. I was also going to flush the trans fluid heater under the turbo, but didn't get around to it.