Engine swap

[The1camperman]

I am thinking of putting a Cummins ISM and Allison 6-speed in my 1973 Eagle.  I will be taking out a Detroit  8V71 and a  9-speed Road Ranger.  I am wondering what your thoughts are on this?  Also looking for someone who has done this to get some detail information.  I am looking for reliability, fuel mileage and more torque to pull a trailer.  We are going to go full-time and travel cross county.  We are new to the group and happy to be here.  Thanks!

[luvrbus]

Plenty of help with that conversion on the Eagles board www.eaglesinternational.net I can tell you now you will need a different rear gear and the lowest you will find will be the 4:10 $$$$

 Me I would drive it Texas and let Sonnie Gray do it and be done with it

good luck

[The1camperman]

Thank you so much for the information!

[TomC]

If you're using a 9spd overdrive, the Allison world transmission set at 5spd will be the same. If the 9 spd is direct, then you can use it as a 4spd. But-with the cruising speed of the 8V-71 being at 1800rpm and the ISM being around 1500rpm, I'll bet you won't have to change the rear end ratio at all. What rear end ratio do you have now and what tire size are you using? The ISM and 6spd Allison is an excellent choice. You'll probably gain 1mpg. Also, you're torque, performance, etc will increase dramatically. Going from a 800lb/ft engine with a manual to a 1550lb/ft engine with an Allison will make a hot rod out of the bus-you'll be tickled pink. Good Luck, TomC

[luvrbus]

If he wants the benefits from the 6 speed Allison OD he will change from the 3:73 to a 4:10 TomC to make the transmission lubricate right,that setup is not a plug and play in a Eagle

 He will fight getting the angle and tilt right sometime it takes several tries rolling the engine combo in and out to get the drive shaft to clear the housing  

He has his work ahead of him fwiw why go to the trouble and use only 4 or 5 gears on a 6 speed transmission that would make no sense to me 

He will be into the swap about 10 grand plus the engine and transmission before he is finished doing the work himself   

The Eagle board will be a great help for him to many there know all the pit falls as BTDT and have the T shirts  

good luck

[wg4t50]

My setup uses the ISM500 withd the 4000R and the 3.9 rear gear, works great,  60 mph is aout 1400 rpm in 2 nd o / d, great fuel mpg etc.
Will need a savy tech to do the computer wiring/interfacing, the mechanical is simple straight forward.
Do NDot use the 3000 series, it will not handle the torque of the ISM.
Dave M

[The1camperman]

Tom C  The 9 speed is a direct drive.  Gear ratio is a 3:70 tire size is 11R 22.5 which is 500 revolutions per mile.  My calculations tell me that the gear ratio would work.  Some of the questions I have are:
 Will it fit using the drop box?
 Will I have to move the radiator back to fit the air charged cooler?
 What would be the best way to drive the fan?

Thank you for your opinions.

[TomC]

With you're current setup, your realistic top cruise speed at 2100rpm is 68mph. Change to the B500/4000/HD4060 (all the same, just different oil pans) and 5th (.74 overdrive) you'll cruise at 1483rpm at 65mpg-perfect for the ISM. If you want to do 75mph, then in 5th you'd be at 1711rpm and in 6th (.64 overdrive) you'll be at 1480rpm-once again perfect for the ISM. I would not change the rear end.

As to fitting with the drop box-I would mount the engine as far back as possible-even maybe designing a "hump" in the rear engine door. The longer the drive shaft, the less U joint wear you'll have. I've seen some that converted the Eagle back to the 1 with the drive axle in front with the tag behind for more drive line space. Course then you loose some storage space.

I would keep the radiator on the left side and mount the air to air intercooler on the left side where the old A/C condenser used to be. Make the dimensions of the air to air intercooler such that you can mount an air to oil cooler for the auto trans side by side. Most all buses now use hydraulics to power the fans. Then you can engineer the mounting outside the bus, and all you have to hook up is the hydraulics once in. Also-if you make the radiators on swing outs, you'll have great access to the sides of the engine and be able to run the engine with the radiators swung out. Find a junk bus with the hydraulic setup and at least use that for your template to build your system. Lots of work, but worth it in the end. Good Luck, TomC

[luvrbus]

Your need to buy the Cummins install drawing #3107317 and the Allison TD 148 pages it explains all the gearing and what is needed it takes the guess work out of it

The 4000 mh will come in 3 different ratios for 5th and 6th overdrive  0.64 and 0.76 the most common  

There will be no problem installing the ISM with a drop box the way it sets no need for a hump just get the tilt and angle right.  

Eagle when they came with the M11 the inter cooler and radiator were mounted side by side on the drivers side and used 1 fan I have the drawings if you need one  

Jim the rv guy has fought the intercooler on the opposite side for years with his 60 series I think he is still working on it with electric fans  

The best way to drive your fan is use a Prevost angle drive and shaft at the top of the fan drive there is one for sale here in the spare tire section I have the drawing also for the Eagle fan drive it is almost the same as a Prevost if you need it

 Boomer here on this board and on the EI board has a ISM in Eagle along with Bill Pratts and others Bill's was installed by Southern Oregon Diesel both can tell you what is needed and there is no hump   

 Not that it makes much difference but you will have 3:73 gears in a Eagle


good luck

[The1camperman]

Thank you Tom C and luvrbus for the information!  This is exactly the type of information that I was hoping for.  I am comfortable with the current rear end ratio, with the overdrive transmission, I think it will be exactly what I need.   My generator is in the rear right side compartment where the ac condenser was so I am planning on putting the inner cooler and transmission cooler in the left side.  If I can get the drawings from you luvrbus that would be great 

Also the Cummins drawing and Allison TD you mentioned,  is that something I can get at a dealer or can I get it online?  Do either of you have contact info for Boomer or Bill Pratts?  This is in the early stages of information gathering, but time to move forward as we plan on full-timing next year.

Thank you both.  Tom from NC The1camperman

[rv_safetyman]

Yes, I have fought the CAC on the passenger side from day one.  I am now using a hydraulic fan, and an enclosure to make sure the fan is not fighting the engine fan.  I also have to use misters on the big hills to keep the manifold air temperature below 150*

Since that area is already spoken for, the CAC will need to be installed on the driver side.  That can be a challenge.  The engine is offset to the driver side and that really makes it tough to stack the CAC and Radiator.  Bill Pratt's is stacked and it was a tight fit.  Byron Pigg has the side by side factory unit for his Series 60.  In my opinion that arrangement compromises both the radiator and CAC.

We have one member that has an Eagle with a Series 60 and the radiator/CAC in the rear (normal truck orientation - reversed for the bus).  That seems to work good.  They had to build an enclosure in the back to cover the extra length.  That makes the fan drive very straight forward and gives great access to the engine from the side - not so much from the back.

If you do the conversion, be sure to get something like the SilverLeaf VMS system so that you can accurately monitor both water and charge air temperature.

Jim