Is this second large "radiator" exclusively for the dash air?

Where would a tranny cooler go and where would the inlet outlet be hooked up to?

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Yup, it is just for the dash air.

A tranny cooler without a fan would would go in front of it. A tranny cooler with its own fan would go underneath the chassis.

I removed my dash air to take the heat load off the engine's cooling system. All the heat from the dash air condenser goes through the radiator. All the steep grades out here have signs saying to turn off AC before starting up the hill.

Dash air does not cool well, anyway, and is expensive to service. It also costs you mileage. Running your genset and roof air does not heat the engine and cools better, and saves fuel. Plus, your genset is happy when it is run.



[This message has been edited by bill h (edited July 10, 2004).]

Short answer to John's query (which seems to have disappeared) on coolers:

It depends.

Long answer:

Perma Cool is a good company and makes good products. Summit is a good company and sells good products. Different motor homes have different heat loads and different coolers have different capabilities and ratings. It gets worse, folks. Manufacturers/resellers rate their coolers by gross weight and BTUs. Gross weight ratings are dreamed up by copy writers, and have scant relationship to reality. There is little correlation from manufacturer or, for that matter, within a manufacturer/reseller's line. BTU capacity is, or should be, a little more standardized.

I would recommend a Tru Cool Max #4739 from HERE:

http://www.bulkpart.com/cgi-bin/miva?Merchant2/merchant...&Category_Code=TCCHD

I am presently using a 4589, and it is not enough on long, hot climbs with a toad. However, my 502 puts out a bit more torque than most RV engines. YRMV. As a result, I have purchased a 4739 and will be adding it soon. I have found GVW ratings to be unreliable. There seems to be a disparity between GVW and BTW ratings, even within product from the same company. BTW, these are made by Long in Canada and also sold under the B&M name here. The only rating that means anything is BTU capacity under standard conditions. The 4589 is rated at 20,500 BTUs, while the 4739 is rated at 40,000. With the 4739, you pay twice the price and get twice the cooling, but you only do it once. As a middle ground, the 4590 would be a good choice. It is rated at 29,200 BTUs. My gut feeling is that the 4590 would be OK for you, but I can't say for sure. My last P30 came with a big cooler installed by the previous owner, so I don't have any particulars on it.

All three are very easy to install, having two sturdy flanges on each end.
The 4739 seems to offer the most cooling ability for the money. You can go crazy and buy a really neat Swedish one that all the racers use, but they are pricey. I have a link if anyone is interested. Jag V12s have good oil coolers if you can find one in a junkyard.

The 4739 is perhaps more than you need, but that is a good margin of safety. Routing the oil through the radiator cooler after the 4739 will allow the coolant to reheat the trans fluid in winter to prevent overcooling.

The world is full of folks who wish they had bought a bigger cooler the first time. I count myself among those. I believe Brandman also found his cooler inadequate towing across the desert.


Switching to synthetic tranny fluid will help, too. It takes the heat better and often runs cooler.

One more thing: There are several coolers with their own fan mounted on them. They are intended for mounting out of the air stream, such as underneath the chassis. I have not used one, but they would be a good idea for anyone who generates a lot of tranny heat in slow traffic or tight boondocking parking. . In our own case, we boondock almost exclusively, and are often in really rough spots requiring a lot of backing and jockeying, often uphill and back and forth. It takes a lot of power to get up on the leveling ramps. Without a lot of air flow, the tranny really gets hot, so I manually activate my electric puller fan mounted just behind the radiator.

OK Bill this question will show my naiveté. Does the transmission have a fluid pump? How do you get the fluid through the cooler?

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Bill,
Thanks, I like the 4739 too. Problem is I already have a engine oil cooler, a power steering cooler and two electric fans in front of the engine water and a/c radiators now. The cooler from Summit is supposed to have a fan that comes on at 215F, and I can mount it under the chassis...... grrr, decisions!
P.S. just got an "out the door" quote of $3196 for a Gear Vendors O/D from Camping World (no tax in Oregon). How's that sound?
Cheers, John

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Dave, yes the trans has a pump. It already pumps the fluid through a cooling tube in either the right or left side radiator tank. The add on cooler is connected in series with rubber hoses.

John, CW is often the high bidder, and their installation quality is all over the map. You might check with Eric's RV in Sequim. Roy knows more about them. The GV comes with a sort-of computer that is not necessary if you are comfortable with a simple OD/DD switch. You might inquire on that to save some money.

As to coolers, have you inquired on the BTU rating of the cooler you are looking at. Heck, if ram air does not cool my 4739 enough, it is going to get a Camaro fan from stock. In my own case, my radiator will probably handle the added thermal load of the hot air from the 4739. If my engine gets hot, then the 4739 goes underneath. A couple of 8 inch fans from Southern Rods would be a neat fit on it.

Have you considered removing the dash air condenser? It improves air flow, removes a lot of thermal load from the radiator, and lowers doghouse heat.

Way back when I was really poor, I disabled the AC in a tow car and used the condenser as a tranny cooler. Economics forced me to choose between air conditioning or a cool tranny.