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4 Speed to Allison automatic conversion Bill 6-20-05  
I was forced into early retirement this year due to losing my left leg.
A friend has offered to sell me his very well maintained 4501 Scenicruiser conversion. Problem is it has a manual transmission and I can’t push in the clutch now.
What sort of money and headaches would be involved in converting the unit to an Allison automatic ? Motor is a
DD 8v71 I would have a local dealer provide the install
Re: 4 Speed to Allison automatic conversion George 7-3-05  
I don't like knocking other people offering advice, but if Marvin doesn't even know how the engine sits in a 4501 after 45+ years of these buses operation, how can he give advice?
The 8V71 sits straight in a 4501, and has since it was put in in place of the two 471s in the early Scenics.
The proper replacement trans is an Allison HT740, (4 speed) or IF there is driveline room, an HT754, (5 speed.) The 5 speed is the trans of choice, as the bus will accelerate better, and do better in the mountains. Both of these trannys are available as used, good, take-outs, for $2000-$2500 exchange. You should expect to pay a SMALL core charge, as your stick won't qualify as the core. You will also need a shifter and its related wiring/tubing, an oil cooler changeout, and a driveshaft modification. These engines use a lube oil cooler mounted on the side of the crankcase, and your new Auto trans also needs its fluid cooled. So, the original single cooler comes out, and gets replaced with a dual cooler. Then they will have to make new lines to fit...
Bottom line? Marvin's price will just about buy the parts, definitely NO labor! Sorry,

PS: Enter Allison Automatic Transmissions in your internet search and it will bring up a truck parts dealer in Ohio & Florida that has a BUNCH of trannys for sale with prices listed. They do duplicate their listings, but they still have plenty!
Re: 4 Speed to Allison automatic conversion marvin 6-22-05  
Bill: Is the engine sitting sraight in the coach ar is it sideways? Either way Allison has a set-up that will fit. I have a 74 4905 with a v-drive and the tranny is adaptable with a v-730 and they have a straight set-up called 740 and you can expect to shell out around 4-5000 for a turn key job good luck
Re: 4 Speed to Allison automatic conversion Tim Owen 7-7-05  
You ought to call B&R Bus Sales in Winters Texas and talk to Keith. They may can beat those prices and they are good people. I for one need to get an automatic install at some point and time in my '83 Prevost.
Re: 4 Speed to Allison automatic conversion Ed Carroll 9-10-05  
HB Industries in southern California makes a bolt on kit to operate the clutch with an air cylinder on the GMC V drive transmissions. They might be able to help you on the 4501 also. Even with the special features you might need it would probably be a lot less than an automatic and give better fuel mileage also. You can see it at
Re: 7Speed to Allison automatic conversion Lewis McCord 12-24-08  
I have 85 wide body custom entertainer Eagle.with a seven speed would like imformation on changing to allison and who is capable to do this work. I'm in central Indiana. Not many coach mechanics here.Lewis
Re: 4 Speed to Allison automatic conversion SGT Schmid 10-3-05  
I have a 95 GMC 4x4 Z71 that looks just like new but it has a lot of miles on it and the trany whent out on it when I was home on leave from Iraq this past month and was thinkng about putting in a Allison automatic in my truck. What would be the beast way to go when I get home from over here?
Re: 4 Speed to Allison automatic conversion Jack Sexton 6-22-10  
Where can I find information on changing 4 speed to allison 740
in 1972 MCI 7
what is involved
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