auxilary trans cooler line routing

[DieselD62]

Hello,

Have an 84 C20 6.2 with an external trans oil cooler out in front of the radiator. Doing a trans swap right now and taking time to address other issues....one of which was the old dried out hoses going to said cooler. I noticed it was routed through the cooler inside the radiator then out to the external cooler and then back to the transmission.

Since heat is not exactly a friend of the 700r4, would I be wise to follow this routing again, or simply go to and from the external cooler and plug off the radiator cooler? Pop says that the trans oil needs the heat of the engine to assist in shifting when you first start out in the morning. OK, but what about when you're been on the road for an hour? I'm not getting something here... you're dumping the engine heat into the trans fluid and then cooling it off immidiately thereafter. Since I have a 195 degree t-stat and the ideal trans temp is 160 in lock-up would I not be negating any trans oil cooling by routing it throught the radiator? I've never been a fan of this stock set-up but never fully understood why. Can someone walk me throught this.

Thanks,
Dave

[BobND]

I can't answer your question with an "absolute" answer, as I have seen coolers hooked up many different ways, seemingly with no different, or "bad" results.

One thing to remember, the oil returned from the cooler enters (in most cases) the tranny's "lube" circuit, where it passes through passages in the case, and through hollow shafts to lube the gears and bushings.

So, cold or warm, you want to keep the cooler flow going, as it lubes the tranny.

I recently installed a rebuilt tranny a customer had bought from a big-name rebuilder, and it came with tee's, and a cooler. They wanted the new cooler tee'd into the lines at the radiator, so the two coolers were hooked in parallel.

Their theory was that LOTS of lube flow is AT LEAST as important as keeping the tranny temps down.

You had to sign off on the warantee card that the coolers were connected as they requested to validate the warrantee.

So, there's another connection scenario to mull over!

[Nelsoncat]

I was just on a website yesterday that builds hipo 700r4's. In his narration on the building of a bullet proof 700 he said the biggest mistake people make is using only the aux cooler and not the one in the radiator. He said they need to be run in series, radiator cooler first and the aux second, otherwise the oil is not cooled sufficiently and tranny failure occurs. His explanation was this "if you wanted to cool a hot piece of metal would you put it in front of a fan or cool it in water?" I think we all know the answer to that and to be honest, until I read that I never really thought of it that way.

Craig

[doncannon]

wonder if this is true? I could have plumbed my lines wrong???? I replumbed them up the passenger side instead of the driver side. Hope it does not over heat it. :eek:

anythoughts?

Don

[BC Clark]

That's what I've done. I also installed the Permacool spin on oil filter with temp gauge. I have that first so the gauge reads exit temp, then the radiator cooler which will provide the biggest drop (but can go no cooler than the what the radiator is running) and then the aux cooler. This set up seems to be working fine for me.