As they say, if it wasn't for bad luck I would't have any at all!  Bottom line is that I now need to replace my engine.  The question is what do I replace it with?

A.  A different rebuilt 440-I.

B.  A used 8.1L GM Vortec with a matched 5 speed Allison.

C.  A used 6.6L Turbo Duramax diesel with a matched 6 speed Allison.

Each of the different paths have advantages and disadvantages.  I have a leaning in a certain direction, but I don't want to influence others opinions by taking a stance at this point.  I would like to hear others opinions of which path to take, but more important than the conclusion are the reasons why a particular path should be or not be taken.  It is those reasons that I will use as input to my final decision which will have to be made before long. 

All three options must be based on retaining the existing gearing of the differential.  The gearing ratios of the Allison's are posted in the file section of the FMCMotorCoach2 Yahoo site.

Complexity obviously increases as you move from option A to option C.  The cost of A and B aren't that far apart as a used Vortec and trany with wiring harnesses, computers and exhaust system components is about the same cost as a fresh rebuilt 440-I.  Installation would be higher with B. Obviously C has the highest cost, but potentially also the greatest benefits.

I really need as much of a discussion of the pro's and con's of each as possible so that I can have as much info as possible to make my ultimate decision.  If I am going to make a change in configuration, now is when it must be done.  I have excluded other engine and transmission options so we can restrict the discussion to the three configurations outlined above. I might say that I already have an Allison 545 installed with my current engine so if option A is selected it includes that transmission.

I thank you for taking the time to give this your reasoned thought,

The following is a copy of a posting I have made in another forum.  It gives others an overall description and a status report.  I am reposting it here so all will be informed.

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Since my last posting, I was able to make contact with the current owner [he did not do the conversion] of the FMC that was converted a few of years ago and written up on The Diesel Page. He surfaced at an FMC rally held in Colorado last month. While I wasn't able to be at that rally, I have received some very complete descriptions of how the conversion altered the fuctioning of the coach. Those descriptions were all good!

Here are a few:
"The coach has a 5-speed model 1000 transmission. It turns about 1700 rpm at 65 mph." [note: In my opinion that is too slow.]
"When we started up La Veta pass, Jim Evans [440 carb powered] (in the lead) said over the radio that he wouldn't be insulted if anyone passed him, so I [440 fuel injection powered] pulled out and stormed up the hill past everyone [This included a turbo inline 6 cyl Cummins]. Dave Jacobs followed in the Duramax coach, and when I waved him to come on by, he passed us like we were nearly going backwards! It was very impressive - and sounded great, too."
"Coach #735 performed perfectly, getting 11.2 mpg pulling the Bimmer (left in Colo. Sprgs for A/C repair) and 13.8 mpg empty including going over 3 mountain passes over 10,000 feet including Wolf Creek Pass (10,550 ft) which is the curviest and steepest I've ever seen."
"Several miles out from Pagosa Springs, we started the long climb up Wolf Creek Pass (10,857 ft). I suggest that Dave proceed ahead, and they proceeded to disappear again ;-) I didn't push it [440 fuel injected]: we stayed near the 35 mph speed limit at 3500 rpm in 2nd gear (Allison AT545 4-speed) all the way up the climb."

It should be noted that no frame issues were evident with the Duramax converted coach even though it still had the stock frame.

As all of you can understand, having read the above plus additional comments any thoughts of an 8.1 vortec disappeared. It also encouraged me as to the thoughts of converting to a Duramax. I came to two conclusions: for this conversion, it needs to use the 6 speed double overdrive transmission so that the stock 4.62:1 differential can still be used as that combination gives a good transfer of torque to the ground with 65 mph at about 1900 rpm, and that if it would be possible to locate an LBZ it would be best. An LLY would also be fine. The above coach has an LB7.

I then made the mistake last week of typing in Duramax LBZ in the search window of eBay! To shorten the story, I am now the proud owner of a used LBZ that was obtained at an attractive price! I guess I am now commited.

The following is the body of an email I wrote to a fellow FMC owner:
"What this purchase did was commit me to a methodology in that I can no longer look for a matched engine/transmission set. It is now piecemeal and just do the stuff that has to be done to make the pieces work together. That will take awhile. One of the reasons I went ahead is that a matched Duramax LBZ and Allison MH (Motor Home) transmission doesn’t exist. No motor home manufacturer has used the Duramax to this date so they aren’t matched to a MH transmission. Motor home manufactures have either used a gas engine or Cummins or Powerstroke. I already had eliminated those engines so I had effectively eliminated a matched set with the MH transmission. That left the possibility of a matched LBZ with a 6 spd Allison, but one that would have to be converted from a standard arrangement to the MH version with the driveline parking brake. Given the attractive price I paid for this LBZ, I went ahead and set pattern.

"Now the game plan is to obtain a matched ECM (engine control module) and TCM (transmission control module) from a Duramax LBZ / 6 spd Allison equipped wreck including wiring harness(s) if possible. That will be used to control a used Allison 1000MH 6 speed. This will be a challenge to obtain as the 6 speed is 2006 or newer, but this is why the year or more timeline to complete the conversion. In my dreams, I would prefer to use the Allison 2500MH with the lower first and second gear, but the population of those is so small I can most likely forget it. Which ever model Allison (1000, 2200, 2500) I do end up using, I do want it to have a parking pawl. Not all of them have one. [Note: the 2550 has the pawl.]

"Then comes the question of how to control the transmission. One possibility would be to obtain the push button, paddle controller found in some newer motor homes. It is 100% electrical I believe. This could most likely be mounted on the inside of the drivers door (or left side of the drivers seat stand) and, therefore, not be involved with the dashboard or driver/passenger area. Whether or not it could be mounted into the dash in the area of the existing shifter is not known.

"So the “you” part of the “we” is to start looking for the pieces and parts needed to complete the job. Start crawling through the junkyards looking for donor vehicles for the above items.

"Understand that I am not committed to the actual conversion until all component parts have been secured. The Duramax LBZ that is now on the way can be resold if all other components are not located at a reasonable price or if some other issue prevents the conversion."

Who am I kidding!!  I am now fully addicted to the conversion of my coach to a Duramax LBZ with an Allison 6 speed behind it and ALL issues will be surmounted.

You now have the current status and know what some of the additional parts needed include. I am going to try very hard to get hold of a 2550MH transmisson. The lower gearing of the first two gears may over time prove to help alleviate any frame issues as the torque is then easily transfered to the wheels when starting out without needing a stiff frame to hold the engine back from rotating.

Wish me luck and if any of you come across any of the items I need (everythng!) please give me an email at Stephen at Heinrichs dot com.

I will post updates as major events happen.

Here is a general description of the engine from a TopKick Truck brochure:

DURAMAX DIESEL 6.6L V8. For the dependability, fuel efficiency and torque output benefits of adiesel, there™s the Duramax Diesel 6.6L V8. Its advanced durability is the product of features like a deep-skirt block with induction-hardened bores, nitride treated forged steel crankshaft, oil-spray piston cooling and a gear-driven water pump and camshaft. The Duramax Diesel 6.6L V8 is also remarkably quiet, due in part to full electronic fuel injection controls that provide pilot injection capability. Pilot injection first introduces a small amount of fuel into the cylinders, followed by a slight delay before the main pulse of fuel is injected. As a result, the combustion process starts on a smaller scale and builds progressively, for smoother and quieter operation.

Max HP is 360hp at 3200 rpm.

Max torque is 650 ft.lbs. at 1600 rpm.

If I have done it correctly, just above this is the HP and Torque curves for the LB7 Duramax as of 1999 when introduced. If I have not done it correctly, then go to the Album section and see the album named Duramax  Note that my engine developes a little more of each, but the pattern would be about the same.  By having a relatively flat torque curve (the area between 1500 and 3000 rpm) the transmission can gear down to increase the engine to ground mechanical advantage and increase the rpm and still maintain torque output.  This enables downshifting to increase the gear ratio between the engine and the ground when under load which transfers the needed torque to the ground while needing less torque from the engine due to the mechanical advantage achieved with the lower gear.  For example, less engine torque is required to climb a hill at the same speed if a coach has 19.5 tires and a 4.62:1 ratio rear end than the same weight coach with 22.5 tires and a 3.90:1 ratio rear end.

Leslie, do you have the torque curve as a graph or table for the Detroit 8.2T?

Definition of Torque: In physics, torque (or often called a moment) can informally be thought of as "rotational force" or "angular force" which causes a change in rotational motion. This force is defined by linear force multiplied by a radius. source: Wikipedia.com

An illustration is a horizontal wrench attached to a bolt. If a one pound weight is hung on the end of a one foot long wrench, one foot pound of torque is applied. Change the weight to three pounds or the length of the wrench to three feet and three foot pounds of torque is applied. A three foot wrench with a three pound weight then exerts [3X3=9] nine ft.lbs of torque.

Now let's apply that concept to two FMC coaches. One has a 1560 lb. Detroit 8.2T diesel installed. The other has an 835 lb. Duramax installed. Furthermore, let us assume that the center of mass of both of the engines is 1.5 ft. to the rear of the attachment point of the engine mounting subframe of the coach. 1560 minus 835 equals a weight difference of 625 lbs. Multiply the differential weight (625) times the length of the lever (1.5 ft.) equals a differential torque force of 937.5 ft.lbs. of torque. This is a constant differential force.

Now if the Duramax puts out a maximum torque of 650 ft.lbs. at full throttle, the additional torque applied to the coach is about 2/3 of the differential torque applied to the other coach with the Detroit when it is standing still. In other words, the Detroit equipped coach is under more stress 24 hours a day, 7 days a week, 365 days a year than the Duramax coach is under for the limited amout of time that it is at full throttle. Of course, the Detroit adds an additional 500 ft.lbs. of torque when it is at full throttle!

Given these numbers, it is my opinion that the structual requirements that are required for the Detroit are much greater than the requirements for the Duramax and so it is incorrect to apply the requirements of that engine to the Duramax.

Stephen

This guys might be able to come up with a electric shift kit to control your Allison.

http://www.retrotekspeed.com/products/smart-shift/smart-shift-stand-alone/

You can have F1 style padlles behind your steering wheel!!!

Kjetil