Transmission oil cooler?

[bevans6]

I need to get one for my MT-647, I guess.  I was looking at a fan cooled 12" by 12" cooler, 1/2" NPT ports, but I really have no idea what I need.  I haven't been able to find a spec for either flow or cooling efficiency.  I guess I should also put in a thermostat switch to control the fan, but at what temp?  Where do people put them in a MC-5, behind the radiator seems a tad inconvenient.

Thanks, Brian

[luvrbus]

It's 8 gpm flow for the Allson and set the fans to come on at 205* but anything between 200* and 250* will work, the Allison does not like cold operating temperatures fwiw    

[lostagain]

Brian, I don't have the Allison manual in front of me, but during normal driving, the transmission is at 180*F, just like the engine. My HT740 is cooled by the engine double oil cooler. The temperature sensor is at the top of the converter, near the oil out hose that goes to the cooler. In hot weather and or climbing hills, the temp goes up from there to 200, 210*. So common sense would tell me to have the fan turn on at 180. I recently installed a filter on that line. I think it helps cool, at least marginally. And of course there is a filter on the other side of the transmission, also remote, all 1" lines. If I installed an oil to air cooler, I would put it beside the engine on the driver's side, just outside the cradle rail. I have space there since I replaced the muffler with a resonator.

JC

PS: I see Clifford says 205*. My trans temp doesn't go that high unless pushed.

[luvrbus]

I got my transmission temps mixed up with engine oil temp the 600 series run between 160* and 220* but I still set the fan on 205* 

[TomC]

I wanted to relieve the radiator of some of the heat from the transmission cooler. I added this cooler http://www.transmissioncoolers.us/DB-341DC-12.html . The hot transmission fluid comes out of the transmission, through this cooler then to the normal shell cooler. Then I'm assured of not running the transmission to cool-the radiator water to oil shell cooler will also keep the transmission running warm on a cold day. I have the aux cooler mounted on the right side engine door with the fan pulling air from the engine compartment to outside. You say that's in reverse-well I found that the big engine radiator fan creates so much pressure, the trans cooler could not over come the pressure and work properly. So running the fan (it is easily reverseable) from in to out works-even the hot engine air will be cooler then the transmission fluid. I have it wired through a thermostat on the out side of the cooler, and a 0n-off-on switch to either turn it off or continuous on. Good Luck, TomC

[bevans6]

How much cooler area do I need?  Is there another way they rate the capacity of oil coolers?

Brian

[luvrbus]

The area is going to depend on how many passes the cooler has 1,2,3 or 4 passes ,the heat rejection according to my tech manual for the 600 series is 44,500 to 67,500 btu/hr.

I can tell you for sure a 12x12 for primary cooling is not going to work.When Hayden sized mine for a 740 it was 88 square inches double pass and there wasn't enough room.  

So I went with double double engine cooler,they make a remote tube type water to oil like the transit buses used with the V730 it's about 22in L x 5in R I have I removed from a GM but the corrosion is so bad it would be a problem for you    

[bevans6]

I was thinking water to oil but with the 350 hp turbo engine and stock MC-5C radiators I don't have any spare capacity.  I will look for a larger cooler, or go with two in series.  They just have that 12 by 12 one on sale at Princess Auto (our version of Harbor Freight, but a little more upscale...).    Thanks for the capacity numbers.


Brian

[Lin]

Here is a link to Hayden.  If you scroll down, you will find recommendations for Allison transmissions.  There is also heat dissipation data.  I did not run our cooling through the radiator, which can be said to be a mistake since the engine heat will not warm the oil in cold weather.  Fortunately, we do not go anywhere very cold.  Ed H. had the same setup we have; that is one cooler in front of each radiator.  The ones I have are about 14 x 11 and have 6 tubes that look to be 1/2 diameter.  I think the fittings are 1 inch fpt.  They could be smaller depending on how think the pipe wall is since I am just guessing from the outside look.  If you are using only one cooler, it will have to be bigger.

On long grades, we have gotten as high as 230, if I remember correctly.  By the time it gets up there, I would be turning on the misters for the radiators anyway.  One surprise we ran into was that the transmission temp would begin to climb when we were going down very steep grades on mountain roads that required us to stay in 1st or 2nd gear.  This, I believe is from the slipping of the torque converter, which does not lock up in those gears for a 647.  If your cooling is going through the radiators, then since the engine is generally running cool in those situations, you would probably be okay.  For us, we installed a dash controlled torque converter lockup switch.  That solved the heat problem plus gave us much more control in mountain descents.  Really, if an incline is radical enough to make you want to stay in 1st or 2nd, you want the transmission locked up.  It makes a huge difference with the Jakes too.  I believe the 740 locks up in 2nd, so those folks have less of an issue. 

[Iceni John]

I've just finished installing a Thermal Dynamics DB-00341DC remote cooler just like Tom C has.   Unfortunately Makco's price is a lot higher than some eBay sellers  -  I paid about $140 more than I could have.   It seems fairly decent quality:  the cooler itself is made in China, and the fan's made in Mexico.   The supplied mounts are rather hoky, but it's easy to make something better.   It has 1" FPT fittings, so they connect well to my -16 transmission hoses.   I repurposed my old Kysor Alarmstat 195-degree temperature switch to turn on the fan, and I also have a sealed toggle switch to override the temperatures switch.   I was slightly surprised when I was testing my new cooling system at how quickly the transmission fluid is heated up by the engine coolant  -  after only a few minutes of idling, the transmission fluid at the new cooler was getting quite warm.   If I can reduce my coolant temps by 5 degrees or more, I'll be happy.   At this point I'll try almost anything!

Yes, I know a larger cooler would be better, but I only had space for the one I bought.   I mounted it behind the rear wheels (but not in the path of debris thrown up from the tire) so it will get the airflow under the bus as I drive.   It's not the ideal location, but it should work pretty well.   I also mounted my hydraulic fluid cooler there as well instead of having it in front of the radiator  -  I don't want anything that can reduce airflow to the radiator or increase its incoming air temperature.   As soon as I finish rebuilding my hydraulic pump and take my bus out for its maiden voyage with a completely new cooling system, then I'll know if my obsessing over cooling details has paid off or not.

John

[bevans6]

What would you think of something like this:  http://www.transmissioncoolers.us/DB-1290.html with dual fans fitted, maybe 10" diameter with 1300 cfm each?  That would give me 38,000 to 52,000 btu/hr, and up to 2600 cfm.  The dual fans would let me run them from 24 volts in series.

Brian

[TomC]

Brian-that's the same cooler but without the built in fan I quoted.

[luvrbus]

Brian,just don't undersized you are like Lin your setup is going to be for primary cooling not auxiliary cooling   

[bevans6]

So it's go big or go home!  A friend of mine has one that I thought was too big, so I will take a closer look at it, maybe it will work.  Thanks, guys, I think I have a handle on this now.  On to the driveshaft...  Next question coming soon!

[luvrbus]

Brian, check and see if the modulator pin is inside you transmission,I may or may not have one for the 600 series I have a sack full of 740 pins