Transmission Cooler

buswarrior · August 02, 2009, 05:03:40 PM

In commercial service, a 644 would have been eaten up and spit out.

However, in busnut service where the duty cycle is light, as is the coach, I don't know how you would destroy a good example of a 644....

IMO, as long as you cool it properly, you won't have a problem related to under spec'ing.

happy coaching!
buswarrior

Lin · August 02, 2009, 06:13:21 PM

BW,
Yes, that seems to be the info I have gotten. A couple of transmission places have told me that the 644 is overrated; that if they install them for various commercial uses, they will last about two years. It is really just a 640 with the torque converter from a 740. Nothing internally has been upgraded. Our service is much lighter though, the MC5's are relatively light, and the bus is owner operated so they can last fine. That might be the way we end up going, but as I said earlier, I have a 740 and was looking to trade it for a 644. One shop says he can shorten it to fit. Someone told me that the 746 was shorter than the 740, so that it is possible to to do. We are waiting to see what price he comes up with to do the job though. If it is reasonable, we'll do it. If not will trade for the 644.

Ed,
Are your two coolers plumbed inline or separately?

luvrbus · August 02, 2009, 06:32:33 PM

Lin, the 746 is shorter but is a electronic transmission never saw one installed a mechanical engine good luck

Lin · August 02, 2009, 07:45:35 PM

Clifford,
I did not mean to say that a 746 was an option, just that a 740 series transmission could be possibly reconfigured to shorten it as this rebuilder claims.

luvrbus · August 02, 2009, 08:18:36 PM

Lin, I had a MCI 5 with a 8v71T and a 644 with a Stone /Bennett never had any problems for the time I owned the bus for 5 years.
The guy I sold it too just changed the engine and
transmission a few years ago so I would not worry about a 644 behind a 8v71.
I am going to call Don and see how the guy is going to shorted the 740 it will have to be done from the front of the transmission I would think.

good luck

Ed Hackenbruch · August 03, 2009, 11:25:34 AM

Lin, they are inline. From tranny to first cooler, to second cooler, to filter, and back to tranny.

Chopper Scott · August 03, 2009, 04:23:14 PM

Just make sure that whatever tranny cooling setup you use has enough gpm capacity to not restrict the oil flow. That could defeat your purpose. Somebody needs to refresh my limited memory of the rated flow that the Allison's require. I'm thinking it was 30 gpm but don't quote me on that. Later