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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: JohnnyPopper on April 22, 2024, 07:29:47 PM
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In replacing my radiator, I noticed the tank fittings were 1/2 inch instead of 5/8, looking inside, the opening was roughly 1/4 inch diameter.
I called the distributor, was told not to worry, aluminum is more efficient at cooling. So much for a 'factory fit' replacement.
The transmission is a '66 GM THD 425, and the cooling lines are definitely a higher capacity.
I thought I could laser measure the temp after a run to see if the trans is running hotter then the engine by a significant percentage.
Being ignorant of transmission design, I don't know if this obvious restriction is severe, or if the 'flow volume' of oil is not that great.
It's not that there are load issues.
The question is: should I worry? and/or add an outboard cooler, bypassing the wimpy one?
As always, thanks in advance for you help!
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A lot of folks will say "run both!" plumb from one to another...I don't subscribe to that theory. I much prefer the solo cooler, as big as you can fit. JMHO.
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Thanks Shifty..need to see how much real estate I have that's accessible. Pretty packed in there.
Thought about calling manufacturer again to ask if they have a volume rating.
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I have always run from the transmission, to the external cooler, back into the radiator cooler, then back into the transmission. I have this on all of my automatic vehicles and have never had an issue in 30 years. I do think however, that it might matter in what climates you are running your vehicles. If you run in cold climates it might help to warm the fluid up a bit before you dump it back into your transmission. That is the theory anyways. I have never tested it with actual transmission temp gauges. There are aftermarket thermostatic control valves that will bypass the cooler until the fluid reaches a certain temperature. Derale and Improved Racing make them, I know.
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Being in AZ, that's never been a consideration for me...I get a choice, hot, or hotter.
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if running inline I always run trans to rad cooler, then to rad to external if you can mount it at the front.
GM ran all of them that way when they did HD trans cooler.
I am currently rerunning my Turbo truck remote as there is no room at the front with the Rad, AC and Intercooler. (pics will be posted)
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Buy yourself them there braided trans cooler lines. You can loop em any which way you need to and they're cheap $$$
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So is the consensus that the severe reduction in volume, i.e. 1/2"ID to 1/4"ID is not a concern?
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I laugh! Amazed that after all these years, with the potent brain trust embodied in this website, that no one will answer the question of volume.
Is it hubris? Many have said that an external cooler is good, mixed with the internal of the radiator, and so on, but no word, answer, opinion, or maybe just a fart, about volume's factor in proper cooling.
Perhaps I'm expected to derive the correct answer from non-direct comments to the question?
Sad.
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Johnny...I will take a stab at it...the factory cooler lines are 5/16" tubing, which means the OD is 5/16". I am not sure what the wall thickness is, but if it is 0.030" then the ID is 0.0253". A standard 5/16" tubing flare nut is a 1/2"-20. 3/8" tubing flare nut is a 5/8"-18.
I would say that you are okay.
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Johnny,
Sounds like you need to figure out an answer based on your own research instead of relying on other's opinion. I will offer my own broad opinion, although it may not amount to much more than a fart.
It seems safe to assume that any reduction in volume could negatively affect your transmission cooling capability. However, there are a lot of factors to consider as to whether the change would be significant for YOU. If this is going in a 1/2 ton Truck driven back and forth to work, probably utterly insignificant. LOTS of these trucks and others like them are driven with NO cooler and survive just fine. If this is a 1 ton Truck driven daily with a 15k lb loaded trailer through the Rocky Mountains, maybe you want to keep the volume as high as possible. Capiche?
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Johnny, sorry I didn't jump in on that.....honestly, the pressures involved are very low, and don't need large passages for higher flow rates....and, the manufacturer of the cooler may have it figured down to a science to keep the fluid in the cooler for a longer time for max benefit.
Maybe check the flow with compressed air, and see if flows to your liking as well. I heard a statement a long time ago that an external cooler doubles the life of an automatic transmission, so I think you'll be ahead of the game regardless.
Cheers!
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Thanks guys!