Cooling The Automatic in an MC7

Stormcloud · March 20, 2012, 06:42:54 PM

We are getting ready to replace the 4 speed in my MC7 8V-71 with an MT654 Allison automatic, but I don't yet have all my 'ducks in a row'.

I'm not sure yet how I'm going to cool this transmission...Jack sent me his article on adding a high-flow cooler to his bus with factory auto, but my bus has no cooling system whatsoever for an automatic transmission.

I've been searching for information on sizing an air cooler for the transmission, but have come up empty.
The MC7s 'apparently' don't have much to spare for cooling capacity, so I would rather not use a water-oil heat exchanger.

Can I cool this transmission sufficiently with a fan-cooled high-flow air cooler only? Do I need to install twin coolers? I am looking at this cooler with a fan added: http://www.transmissioncoolers.us/Merchant2/merchant.mvc?Screen=PROD&Store_Code=T&Product_Code=DB-1290&Category_Code=allison-transmission-cooler

I could add another http://www.transmissioncoolers.us/Merchant2/merchant.mvc?Screen=PROD&Store_Code=T&Product_Code=DB-1268&Category_Code=allison-transmission-cooler
with a fan on the opposite door (above the muffler).

Comments? Suggestions??

I sure don't want to let the smoke out of the transmission.

Thanks!

Mark

buswarrior · March 20, 2012, 09:55:22 PM

You need to know what the max BTU output of the transmission is, and then choosing a cooler is easy.

Also, what size lines and fittings will be required.

3/4 inch might not be large enough for the volume required?

Where are the busnut engineers of days gone by, who knew these things in their heads?

happy coaching!
buswarrior

DMoedave · March 21, 2012, 06:28:52 AM

I would say just by the dollar amount that its not enough! I remember around 500.00 for the cooler we needed. Think summer time and climbing hills. Long steep ones. we have to go to an air cooler as ours is run thru the engine trans cooler and it raises our engine temp as a result in the summer climbing hills. We had transend synthetic put in this past Jan while in Fla at Ocala Detroit. it is supposed to help and seems to have lowered trans temp but i want summer testing.

The cooler we are looking at has 1" lines and is a Hayden i believe. You can google their site, i think they ship from Alabama and have line kits as well.

Jacks article is excellent and lots on the BNO archives, probably here also. We are going to run thru the existing cooler as well since we do run cold weather. We are very happy with our 654 by the way. good luck

Ed Hackenbruch · March 21, 2012, 07:14:46 AM

Mark, when the PO put the 644 in my 5A he put in coolers that are about 1/2 the size of the radiators. He mounted these about 6 inches in front of the radiators. When i first saw these i was concerned that they would be blocking air flow to the radiators plus be putting heat into them. In the 9 years that we have been running i have only seen the temp gauge for the tranny move twice, and once was going up the hill out of Laughlin headed to Vegas when it was 107 degrees out.

My thoughts are that since he used large and long lines to and from the coolers that a lot of heat is shed on the way. I also think that having the second cooler makes a big difference, it increases the volume of tranny fluid. My 8v71n usually runs at 175-180 degrees, however it did get to just over 200 degrees on that trip up the hill. We stopped at Searchlight and took a long lunch break to let it cool down before going on.

I did think about adding misters after that, never got around to it. Since then i changed over to transynd which is supposed to run about 10 degrees cooler, so should put even less heat into the system.

Geoff · March 21, 2012, 07:18:07 AM

You might consider the transmission cooler used with the V730.

luvrbus · March 21, 2012, 07:54:25 AM

Give the guys at United a call and let them size your cooling if you don't have the factory cooler on the engine www.utxchange.com they do a good job and will sell or tell you what is needed fwiw 2 filters help a great deal and adds life to the transmission

good luck

akbusguy2000 · March 21, 2012, 10:32:19 AM

There is an Allison application guide in the Hayden catalog:

http://www.haydenauto.com/upload/HaydenAuto/Documents/Cat_Hayden/2007-hayden-trans-oil-coolers.pdf

There is a wealth of other technical information and guidance there too.

tg

Gary W · March 21, 2012, 10:46:09 AM

Hi Mark

When we had our 1973MCI-7 it had a factory installed Allison 740Hd. The temp gauge would go above 180 even pulling the slightest grade . I installed misters and that solved my problem.

Gary

luvrbus · March 21, 2012, 11:16:18 AM

Gary why would you cool a 740 running at 180 degrees that is fairly cold for one with a factory setup oil cooler they run above engine temp you can get the Allison too cold

Gary W · March 21, 2012, 06:22:37 PM

I said when going above 180, it would hit 200 plus in the summer.

Gary

luvrbus · March 21, 2012, 06:33:05 PM

200 degrees is still in range and some to spare

John316 · March 21, 2012, 06:42:37 PM

Quote from: luvrbus on March 21, 2012, 06:33:05 PM
200 degrees is still in range and some to spare

I only know about our B500, but with the retarder the temps can hit right at 300 or a little over. Running down the road is more like 200 to 225.

I just replaced the fluid lines going to the cooler. Those things are serious money ($500 each), because they have to be teflon SS braid and are over four feet long. Whee.

One thing I did want to mention is our lines are 1 1/8 (maybe 1/16th, but I think it is 1/8). I don't know if you will need that much flow, but that is what ours has (bigger lines because of retarder). Ours is also water cooled.

John

Barn Owl · March 22, 2012, 04:53:46 PM

Keep you eyes on Ebay. I got a NOS Hayden 1290 for $120 shipped. It cost me $160 in hoses to hook it up.

mikelutestanski · March 22, 2012, 05:05:41 PM

Hello; The regular detroit cooler can be replaced with a double cooler which was standard for an automatic transmission installation. I found one on a truck engine. When I replaced my manual transmission I had the engine rebuilt and a double cooler installed. If you don't think that will be enough or if you can't find one then a cooler can be installed on the side door with a fan behind it. As Jack Conrad has done.

SInce then I have replaced the 8v with an L10 with a B400R retarder transmission. My engine runs cool because the double radiators are more than adequate. I kept the radiators for the retarder. I used the original allison cooler (the one that came with the L10,B400r in the transit bus) and interfaced it with the existing system. Works great.
Don't know why stainless steel braided hoses are required. The transit I bought with the transmission used regular hydraulic hose.. Still pricy because of the size and fittings required.
Regards and happy bussing mike

John316 · March 22, 2012, 06:09:38 PM

Quote from: mikelutestanski on March 22, 2012, 05:05:41 PM
Snip----------------------------
Don't know why stainless steel braided hoses are required. The transit I bought with the transmission used regular hydraulic hose.. Still pricy because of the size and fittings required.
Regards and happy bussing mike

Mike,

The teflon SS braided is rated for that much heat. The hydraulic hoses, around here, were only rated up to 250, or so. Found one that was rated up to 280, but not sustained. Our B500 was expensive enough, I was not going to risk losing a line when I need it the most. I really suspect that a standard hydraulic hose would work no problem, most if not all the time.

John