Auxiliary Transmission Cooler

T

Trevor54

New member
I've posted this on a couple other sites, but I figured I'd spread the love. So I ust had my 727 auto transmission rebuilt on my 345 78 Scout "grouchy", and the tranny shop strongly discouraged me from adding an auxiliary cooler. They said that the 727 needs the heat and that, especially in winter, an auxiliary cooler won't let the fluid heat up enough, and that there'll be condensation inside as well. This surprised my mechanic as well, but we both figured we should defer to the expert. Any thoughts? I won't be towing with this anytime soon, and nothing too extreme in the four wheeling either. Thanks
 
I would agree with your transmission shop techs.

From the factory your Scout came equipped with adequate cooling capacity for normal use.

It is possible to overcool to the point you are doing more harm than good.

Even under extreme conditions the stock cooling system should be more than adequate to do the job if you get enough air flow across your radiator. The only time in which you May have problems is if you are working things hard at low engine rpm's.

The only way in which you will know for sure is to plumb in a transmission temperature gauge so you can see what sort of temps you are running.
 
Thanks a lot Mark o. I appreciate all the helpful experience in these forums. I will definitely get a tranny temp gauge when my wife decides that my "allowance" has paid off this transmission rebuild.
 
trevor54 said:
I've posted this on a couple other sites, but I figured I'd spread the love. So I ust had my 727 auto transmission rebuilt on my 345 78 Scout "grouchy", and the tranny shop strongly discouraged me from adding an auxiliary cooler. They said that the 727 needs the heat and that, especially in winter, an auxiliary cooler won't let the fluid heat up enough, and that there'll be condensation inside as well. This surprised my mechanic as well, but we both figured we should defer to the expert. Any thoughts? I won't be towing with this anytime soon, and nothing too extreme in the four wheeling either. Thanks
Click to expand...

I would totally disagree with your "tranny shop" analysis!! They certainly did not explain to you the ramifications of adding an auxiliary heat exchanger in a proper manner!!

Any auxiliary unit should be plumbed in series with the existing setup and never installed in stand-alone mode unless a thermostatic control valve is added to the transmission plumbing along with the heat exchanger.

An automatic transmission uses a working fluid designed to operate within an optimal temperature range. Engine/transmission heat load is handled by the oem radiator package just fine, but for any service involving increased gcwr, then that package quickly is overworked. That is when an auxiliary cooler is called for even for occasional use.

Summer...winter...makes no difference to the powertrain operation if the entire engine cooling system is operating correctly. The radiator and engine cooling system package determines the working temperature of the engine oil and the transmission oil. And all the various "temperatures" are kept under control by the vehicle heat exchanger and the cooling system thermostatic control (if working properly). But when significant added load is added to the system over and above normal daily driving such as towing a trailer, an on-board "overload" of say...sacks of concrete, or slogging up a long incline at low ground speed and high engine rpm (when the transfer case is in low range), an auxiliary cooler is totally necessary in my opinion and I'd never build a transmission for anyone and stand behind it if the rig did not have an auxiliary tranny cooler installed.

The vehicle cooling system for any given engine/powertrain option was spec'd for a minimal ability to provide adequate temperature control for the spec'd gvwr of the individual vehicle. Add in any increase in load above the gvwr and engine cooling overall quickly becomes unmanageable.

That also happens to be the standing policy of the atra and their "member" transmission professionals as far as the blanket warranty they offer on a trans built by an atra member shop.

The effective "normal" transmission oil temperature range for a tf727 is no different compared to any other slush box of that era...a Ford c6, a GM turbo 400, etc. That would be a "low" of about 160f and a "high" of around 240f, these would be temps encountered for an extended period and not just an occasional anomaly.

All the above is in reference to vehicles/transmissions of the era in which we deal with around here. You cannot draw a comparison with more "modern" vehicles that incorporate computer control in the engine/powertrain module. The temperature control of all that throwaway shit is far more complex and involves changing shift points, disabling over drive or converter lockup, putting the engine/trans into "limp" mode, etc.
 
Thanks for the input michael. I'll admit, some of that went over my head, but I'll print it up and show it to my mechanic for a tutorial. As far as the situations you mentioned where the temps would exceed the capabilities of the stock cooler, a long uphill climb in 4-wheel low will probably be the only thing that applies to my Scout. I guess I should also mention that I live in the desert where afternoon temps often get above 110 in the summer. But, I still want to make sure that I'm being safe and not tearing up another tranny. Thanks again.
 
michael mayben said:
inever installed in stand-alone mode unless a thermostatic control valve is added to the transmission plumbing along with the heat exchanger.
Click to expand...

Can you explain this to me in layman's terms? So you would add a thermostatic valve to stop or restrict the flow into the [aux] Cooler if the fluid temp was too low??? I didn't know they made those.


Application would be an off-road truck, no built-in cooler avalaible (aftermarket rad), ridden hard, put away wet, abusing hill climbs in 4low and/or racing.

For any street truck or dd in series with a rad-cooler would be the situation.
 
You can also get a trans t-stat at your local jy in May late model fords. It looks just like the ones offered by B&M perma-cool, and derale.
 
72 with 304 n 727 stock rig no big tires or crazy wheeling planned so if im going to be daily driving does my Scout necessarily need a trans cooler? If so the lines need to run through the radiator to maintain proper trans temp? If you just run lines from trans directly to cooler it could cool the fluid too much n thats not advisable? :nono:I have a flex-a-lite fin n tube cooler. Thanks
 
You definitely need some type of cooler. If you routinely drive in extreme cold temps, an auxiliary cooler by itself could be a bit too efficient for maintaining optimum fluid temp. Other than that, probably okay to run auxiliary cooler only. Plenty of folks do. If you do the bulk of your driving in extreme high temps, your engine cooling system will thank you for not having to cool the trans fluid in addition to the engine coolant.
 
Thanks for your input. Ya im here in southern cali and it never gets cold by any means but it does get hot and lots of traffic n stop n go traffic so I guess better safe than sorry huh?
 
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