1971 radiator question

[dtkarst]

I’m just about to install my rebuilt transmission in the 71 c10 and had a couple questions. It has an external cooler for the transmission in front of the radiator out on at one point for hauling a slide in camper, so I was told. Well I don’t intend on pulling or hauling anything heavy with it anymore so do any of you think it’s okay to hook up the transmission the way it was originally into the radiator? It doesn’t appear to have any plugs in the ports for the lines from the transmission though. It’s either hook them up the original way or Use the external. I will probably change the external if I go that route since everything else would be new

[Steeveedee]

I have an external cooler in series with the stock cooler, but I pull a 6000 pound travel trailer. If you never expect to pull a load, you can eliminate the external cooler. I'd never say never, though.

[dtkarst]

You’re right, I shouldn’t say never. But I’ve got a 2011 duramax that does all my pulling of actual heavy loads, then a 64 c20 that I use to pull a 12x8 utility trailer with a mower rarely. But would the cooler ports on the radiator being open for who knows how long Have messed any thing up On it?

[dmjlambert]

Is the radiator a known age? When I had a transmission shop rebuild my transmission, they installed a new external cooler and left the questionable radiator's transmission cooler section unhooked. They explained it to me if there is any question about the radiator age you should avoid using it, because if the internal transmission tank inside the radiator leaks and engine coolant mixes with the transmission fluid and gets into the transmission, that is going to cause another rebuild on the transmission and it would be expensive as heck. I have since installed a new lifetime warranty all-weld aluminum radiator to replace my marginally-good old radiator, so I would feel comfortable converting back to inside-the-radiator transmission cooling, and will probably go that route in the somewhat near future.

[Ironangel]

Don't let the fear of a leaking transmission cooler wind up costing you another transmission rebuild! I happen to know how cold it gets in Hay's Kansas and these transmissions need heat to operate correctly. The key is not overheating them! That internal cooler serves a double purpose and one of those purposes is to heat the fluid! Stand alone external coolers are fine in warm climates like California and Texas but I'd never run one in Kansas. They are fine when used with an internal cooler that warms the fluid before it gets cooled again. To cold is almost as bad as to hot when it comes to transmission fluid. If your not towing then just use the internal cooler. The transmission develops way more pressure than the cooling system so leaks go into the radiator "usually" speaking and if the cooler is leaking you'll see it at the cap or the overflow bottle. Your transmission is more likely to suck motor oil or fuel via the modulator valve than get water from the radiator...Do your research and don't over think it!

[Ironangel]

Originally Posted by dmjlambert

Is the radiator a known age? When I had a transmission shop rebuild my transmission, they installed a new external cooler and left the questionable radiator's transmission cooler section unhooked. They explained it to me if there is any question about the radiator age you should avoid using it, because if the internal transmission tank inside the radiator leaks and engine coolant mixes with the transmission fluid and gets into the transmission, that is going to cause another rebuild on the transmission and it would be expensive as heck. I have since installed a new lifetime warranty all-weld aluminum radiator to replace my marginally-good old radiator, so I would feel comfortable converting back to inside-the-radiator transmission cooling, and will probably go that route in the somewhat near future.

That's fine in Texas, but that wont work in Hay's Kansas winters...

[dmjlambert]

Thanks for that education, I learned something good today.

[Andy4639]

You could always take the radiator out and have it tested and flushed out. You can buy the test gauge cap and test it yourself also.I like having both just incase I do have to pull something but it's not a must. Even if it's a large load the internal should handle it. Depending on how far and how fast you want to run it.

https://www.summitracing.com/parts/s...SABEgKA0vD_BwE

[rpmerf]

You probably already know this, but wanted to be sure it was mentioned here. When installing a new trans, ALWAYS flush the cooler and lines with NEW transmission fluid to be sure there isn't any left over gunk from the previous trans.