MagicDragon42 Posted August 10, 2008 Share Posted August 10, 2008 I know someone will know the answer to this easy question. I have a 71 Monte with a 402 and a T400 auto transmission. The other day a noticed I had tranmission fluid driping from the rear of the fan shroud and it was coming from an external transmission cooler assemby on the back of the radiator. The radiator was by-passed completly and the original transmission output fluid line had been replaced with a hose. I have a new external cooler but I also want to route the fluid first to my radiator and then to the external cooler and back to the transmission. My question is: Is the top port on the radiator the input, the output, or makes no difference? I can't locate the info in any of the docs that I have and it seems to me the top port would be the input and the bottom the output. I have a feeling that when I connect the radiator I'll find it leaking and that's why some past owner had by-passed it. Mike Quote Link to comment Share on other sites More sharing options...
bobsmc Posted August 10, 2008 Share Posted August 10, 2008 they probably bypassed it due to prior transmission failure contaiminating the rad cooler with trans clutch debris. i would throughly flush the rad before routing it thru there. i could be wrong but i think the input is at the bottom of the rad. bob Quote Link to comment Share on other sites More sharing options...
FerrariTruck Posted August 10, 2008 Share Posted August 10, 2008 I know someone will know the answer to this easy question. I have a 71 Monte with a 402 and a T400 auto transmission. The other day a noticed I had tranmission fluid driping from the rear of the fan shroud and it was coming from an external transmission cooler assemby on the back of the radiator. The radiator was by-passed completly and the original transmission output fluid line had been replaced with a hose. I have a new external cooler but I also want to route the fluid first to my radiator and then to the external cooler and back to the transmission. My question is: Is the top port on the radiator the input, the output, or makes no difference? I can't locate the info in any of the docs that I have and it seems to me the top port would be the input and the bottom the output. I have a feeling that when I connect the radiator I'll find it leaking and that's why some past owner had by-passed it. Mike More likely than not, Not being able to get it to stop leaking is why the cooler was installed. At least thats why I bypassed my radiator altogether is cause i couldnt keep it from leaking. Hook it up and find out though Quote Link to comment Share on other sites More sharing options...
72MC Posted August 11, 2008 Share Posted August 11, 2008 Top of radiator is the input, bottom is output back to transmission input. - Dave Quote Link to comment Share on other sites More sharing options...
72MC Posted August 11, 2008 Share Posted August 11, 2008 Allan, you are correct. For both the th350 and 400, the best way to remember the lines is, top to top and bottom to bottom. However, on something like a 4l80, the output line from the tranny is in the front and the input tranny line is in the rear. What I have found to be a topic for discussion/arguement is the routing of lines if using both a trans cooler and the rad cooler. On the Monte, I routed the output from the trans to the radiator and next to the trans cooler then back to the tranny like my instructions said. On the Monte, I need the fluid temps to drop fast since it will see track time. However, on my 96' Impala SS which has a 4l60e, the lines are routed from the tranny to the trans cooler first, then to the radiator and back to the tranny. This was the factory setup. I have heard arguements supporting both methods. I am not up for writing a book, so I won't do a long, drawn up response here. In a nut shell, the first method will send cooler fluid back to the tranny causing a wider range of temp fluctuation. The second method keeps the temp fluctuation to a closer median temp. - Dave Quote Link to comment Share on other sites More sharing options...
MagicDragon42 Posted August 12, 2008 Author Share Posted August 12, 2008 Thanks for the help everyone. Top to top and bottom to bottom is the best way to remember it for both the 350 and the 400. Mike Quote Link to comment Share on other sites More sharing options...
kc8oye Posted August 13, 2008 Share Posted August 13, 2008 into the rad.. out of the rad into the other cooler.. that's the best way according to the instructions to my cooler.... Quote Link to comment Share on other sites More sharing options...
MagicDragon42 Posted August 14, 2008 Author Share Posted August 14, 2008 If anyone installs a B&M SuperCooler and uses their instructions 2500356.03, there is an error on the chart of Rear Wheel Drive Transmissions for the TH-350. They show the upper transmission oil port on the transmission as the oil output of the transmission. That is not correct. Both the TH-350 and TH-400 have the same configurations. The oil output of the transmission is the lower port and this line should be connected to the lower connection on the radiator. See http://tciauto.com/Products/TechInfo/cooler_fittings.asp. The output of the radiator (lower connection) goes to the input on the B&M cooler and the output of the cooler goes back to the transmission (upper connection on transmision). Mike Quote Link to comment Share on other sites More sharing options...
BuffaloBillPatri Posted July 27, 2009 Share Posted July 27, 2009 Mike, Thanks for the info, But your last sentence: "The output of the radiator (lower connection) goes to the input on the B&M cooler and the output of the cooler goes back to the transmission (upper connection on transmision)." Should read: The output of the radiator (UPPER connection) goes to the input on the B&M cooler and the output of the cooler goes back to the transmission (upper connection on transmision). BBP Quote Link to comment Share on other sites More sharing options...
Heckeng Posted July 28, 2009 Share Posted July 28, 2009 Ok, I am the odd duck here but I would think you would want to output of the tranny to go into the lower connection on the radiator to eliminate bubbles/air being trapped by dumping fluid in the top. By having the input in the bottom, you flush out any air stuck in the system. Am I crazy or not thinking correctly? Quote Link to comment Share on other sites More sharing options...
Heckeng Posted July 28, 2009 Share Posted July 28, 2009 If it was a sealed system, you would have to bleed it. It is filled with air when you hook up the lines which is what I was thinking about. Maybe it flows enough volume that the air gets pushed out of the system and leaves via the case vent. I don't know. Quote Link to comment Share on other sites More sharing options...
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