My new MC-5C - Allison swap thread!

[4104SoFl]

What size is your garage? (Shop)

[bevans6]

That one is about 48 by 65 on the main floor, but there are three other rooms.  I have another one  about 40 by 65 with a 11 ft by 45 foot parking pad and a 16 foot tall door, and the rest  is wooden floor, I have it set up as a wood shop and usually the bus parks in there.  It's pad is tractionized, not smooth, so the pallet truck doesn't roll as well.  And I have a 28 by 32 heated garage.  Lots of shop, it used to be a fiberglass fishing boat factory (Nova Scotia is all about the fishing boats).  It also has about three acres of park-like grounds, half treed and half mown, no neighbours, and a two century old farm house...  

[sledhead]

nice garages Brian

sure is nice to have more sq feet in garages then in the house  ( just do not tell the wife )

dave

[4104SoFl]

Nice, but too cold for this Florida boy. Still nice.

[buswarrior]

Geez, I'da brought the engine stand down to you, if I knew you were messing with this!!

Another lovely bus upgrade/maintenance adventure documented.

happy coaching!
buswarrior

[bevans6]

For posterity and science, 10 hours, 725 Km and $6925 (Canadian bucks) later I have a freshly rebuilt MT 647 in my shop, complete with flex plate, the correct steel adaptor/spacer, a new neutral switch, reverse switch, shift cable kit and yoke output.  All that I have to make is the crank adaptor, which is really just a spacer, and get the driveshaft shortened.  I have a copy of the official Allison 71 series installation kit diagram, with all dimensions and part numbers, which is a bonus.  The flex plate is going to be delivered in a few weeks, it's a brand new order from Allison in the US.  I haven't decided what to do for a shifter yet.  If I can use the original shift lever I expect I will do so, just to be ornery.

Brian

[bevans6]

I know this is boring but I figure two years from now the next guy is going to try to put an automatic in a MC-5 and might just appreciate this detail of info...

Just unpacked everything and did my measuring to see what will fit.  It sure helps to have a copy of the official Allison drawing (No. AS-04-200, probably any Allison dealer would have that drawing) that shows exactly how this is supposed to fit together.  First things first, do I have the correct SAE 1 to SAE 2 adaptor, and by luck, foresight or skill on the part of the tech who found it in the used pile, I indeed do.  It is Allison part number 6881378, it has 12 bolts on both bolt circles (SAE 1 has 24 bolts, they skip half the 7/16" bolts) and critically is offset by 0.886" -  0.906" (range of acceptable offset) to put the SAE 2 flange the correct distance from the bellhousing, so no additional spacer is needed.  There are new offset adaptor rings available with a 1" offset that could be made to work.

This means I need to make a steel crank hub adaptor that has a 1.7" pilot hole for the pilot on the transmission torque converter, has a register for the ID of the flex plate center hole, a register for the OD of the crank flange, and a thickness of 0.720".  This adaptor will perfectly locate the torque converter with respect to the crankshaft, and make sure the flex plate is also centered on the crank shaft.  The flex plate is bolted to the crank hub by the normal crank/flywheel bolts.  So far, so good!  Next I am going to hang the transmission on the engine and slide it in to measure for the driveshaft.

Another big weather event forecast for this weekend so I may take a few day off to enjoy the probably power outage and blackout...

Brian

[Oonrahnjay]

     Brian, thanks for the clear and complete writeup -- yes, this should be of great help to the next person undertaking this task.  But one question, please; I  understand "thickness" as applied to a "spacer" but what is "offset" as applied to an "adapter"??   Thanks,  BH

[bevans6]

Offset is the distance between the SAE-2 flange on the transmission and the face of the SAE-1 flange on the adaptor ring.  The adaptor is basically 0.9" thick so it spaces the transmission back away from the engine by that much distance.   Other write-ups (Fredwards) have referenced a zero offset adaptor, which is certainly available, and a 1" spacer ring.  Clifford has referenced a 15/16" spacer in the same thread.  This adaptor is kind of all-in-one made specifically for this job - putting an Allison 644/7 or 654 on a Detroit 71 series engine.  The MT-643 has a different torque converter and would need a different adaptor.  The point and purpose of the adaptor is two-fold - one is the obvious adapt SAE-2 transmission to SAE-1 bellhousing, but second and very critical is space out the transmission so the torque converter bolts up perfectly to the flex plate.

Brian

[bevans6]

So anyone with a MC-5 knows that the engine is set at an angle in the bay.  Actually two angles - it's about 15 degrees off the center line of the bus and it's about 5 degrees off level.  This lets the driveshaft point up and over the rear axle and at the flange on the drop box.  So my engine is setting on it's little dolly square with the wheels and legs of the dolly, so it rolls to and fro aligned with the engine centerline.  So when I offered it up to the engine bay rails it starts off perfectly aligned and by the time the engine is in the bay by two feet it's horribly off center.  It only takes me four tries before I realize that I have to reposition the engine on the dolly so the dolly legs are aligned with the cradle rails and not the engine.  Can you say "doofus"?     I'll reposition it tomorrow.

Brian

[Oonrahnjay]

Offset is the distance between the SAE-2 flange on the transmission and the face of the SAE-1 flange on the adaptor ring.  ...
Brian 

    Thanks!