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tlogantx
Senior Member

USA
67 Posts

Posted - 04/10/2006 :  06:45:55 AM  Show Profile  Reply with Quote
I am looking at purchasing a 1995 Thomas pusher. They are several for sale all with a CAT 3116 engine but my question is on the tranny. Some have a MD3060, and some have a MD643. Is one better than the other so I know which way to lean?

thanks, Tim

wagonmaster
Top Member

USA
2298 Posts

Posted - 04/10/2006 :  08:21:54 AM  Show Profile  Reply with Quote
I'm a little puzzled. The MD 3060 is an electronic transmission, comtrolled by the engine computer. The CAT 3116 is a "mechanical" engine, with little (or none at all)computer controls. My guess would be that the MD 643 is the correct trans. for a 1995 model unit, as they weren't available until 1998 or so, I believe. At any rate, the MD643 is a "direct drive" transmission, without an overdrive high gear, capable og GVW weight ratings up to 35,000 or lbs. The MD3060 is a six speed (maximum-but can be programmed for only 5 gears) double overdrive transmission, of similar weight capabilities. 5th and 6th gears are both overdrive, in most cases. If in fact, the MD3060 is the transmission being used, it will provide good service and much better fuel economy than the MD643 due to the overdrive slowing the engine down to a lower RPM in cruise mode, on the road.
Good Luck!

Joe
Land of the Free, because of the Brave!
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Mechan1c
Top Member

USA
841 Posts

Posted - 04/10/2006 :  11:19:50 AM  Show Profile  Reply with Quote
Hey Joe & Tim, Our first buses with MD's were 1995 Thomas WestCoastER's with 275 HP "9GK" 3116 CAT's. The transmissions came with stand-alone Allison "Vehicle Interface Modules." I still have 2 of these. The year before we specd the 3116, but the 643 was the only choice.

As far as the original question; which to buy? The MT643 will be much less to rebuild or replace if need be. It's also a good workhorse trans. Like Joe said, the MD being an OD, is a better choice from a MPG and road speed standpoint, but they are expensive to rebuild $$$. The 2 buses I have with these early MD3060's had trans rebuilds at about 120K in 2003, which was a bit of a surprise and dissappointment. I remember the clutch material being about gone. I would say if I knew one of the MD3060 buses had a fresh trans, I'd go that way. Depending on the fleet, the manager may tell you the mileage on the trans. Other signs would be an Allison rebuild tag on the trans w/a S/N. Just a thought...Tom.
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wagonmaster
Top Member

USA
2298 Posts

Posted - 04/11/2006 :  03:42:00 AM  Show Profile  Reply with Quote
Good points, all, Tom! No wonder the MD3060 worked with the 3116, you explained it! Having a "stand alone" transmission would be cause for consideration as well, but Tom's are going after a rebuild. No question the MD643 is far less expensive to rebuild.....Like the man says. " you pays your money and you takes your choice"!!

Joe
Land of the Free, because of the Brave!
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IC
Top Member

USA
3413 Posts

Posted - 04/11/2006 :  9:14:06 PM  Show Profile  Reply with Quote
I thought the man said, "you pays your money and you takes your chances". Different man, I guess....
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ModMech
Top Member

USA
948 Posts

Posted - 04/13/2006 :  08:37:33 AM  Show Profile  Visit ModMech's Homepage  Reply with Quote
I would go with the MD 643 myself, they are VERY durable and will be less than 1/2 the price to repair if they fail.

If you want customer service, you NEED an International!
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ColoradoBusmech
Active Member

USA
10 Posts

Posted - 04/18/2006 :  7:15:45 PM  Show Profile  Reply with Quote
My experience has been that the MD lasts longer than the MT643 before failure but, as stated previously, a rebuilt MD is much more expensive.

One constant problem we have with our pre 98 buses is that the TPS for the MD has a high failure rate. We also have the occasional electronic glitches with the MD.

Personaly, I would pick the MT643 for an older bus.
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