hurstssamx said:
DDoyle said:
The M911 also used the 14.00-24 20-ply tire - although a different tread pattern, these should be available reasonably on the surplus market, should you chose to go that route.
A concern would be how many RPMs can the front axle and steering knuckle can stand. The axles under the ten ton are duplicates of the ones under the WWII-era Mack NO - which had a top speed of something like 32 MPH. Duplicate as in the same part numbers. I am certain that the Mack engineers did not envision the kinds of revolutions you do - and loosing a tire/wheel/hub/knuckle assembly would make for a very bad day - not only for you, but for anyone else on the road in a half-mile radius.
The weak link in the diesel ten ton is not the V8-300 Cummins, but the triple reduction front axle.
DD
My dad did the same engine trans plant i am. . . He how ever ran a completely different Gear box. . .
His front axle is holding up just fine. . . runs the truck 45mph puts about 1,500 - 2,500 miles a year on it !
his engine is a stock KT-600,
KT-stage3: 600hp@2,100rpm and 1,650tq@1200rpm.9spd OD .76:1 2spd OD .85:1 so his final OD is .61:1 engine speed at 2,000rpm = 2,780rpm. . .
2,780/10.11=274.97rpm
the KT i got is running a bit more power,
KT-Cummins i have : 635.2hp@2150rpm 1735.6tq@1375rpm. Road ranger 13psd OD .62:1 engine speed at 2,000rpm=2760rpm. . .
2,760/10.11=272.99
Being late on a book deadline, I don't have the time to reread all the posts in this thread, but I thought at one time you mentioned raising the top speed of the truck, supstantially. My stock M123A1C runs 45mph, the same speed as your father's - so lubrication of the rotating portions of the driveline on his truck are clearly within the specs checked by Mack engineers when the trucks were designed in 1955. They did not check the specs at 50-60 MPH - which I thought was the speed you are seeking (if my memory of your intent is bad, I apologize). If this is the case though, it would be worthwhile to put in a call to Allentown and ask someone in engineering. You may be willing to take a chance, but the mom and kids in the car beside you as you go down the road did not sign up for these chances.
On another subject - the design of the truck and general "improvement". There is no such thing as the perfect military transport vehicle. But, they are designed to meet certain common goals. The truck must be able to operate in North America and Europe, and in the desert, in the jungle and in near arctic conditions, without modification, adjustment - and without overheating. The power train is specifically designed so that the least-robust component is the engine. That is to say, by design and intentionally, the engine is not powerful enough to snap axles and twist out drive shafts. These components are "over-engineered" around the engine. If you twist out a driveshaft on the way to a show, its an inconvenience. If your dad snaps an axle pulling a stump, he loses some pay - if a GI tears out a driveshaft, this could cause someone to die. So, better that occassionally another truck be used to help pull, than fit a more powerful engine.
Also, and again, I don't have the time now to dig up the documents - these trucks were designed to be driven off-road something like 70 percent of the time. The need for speed was nil. The Red Ball Express was/is famous for their high-speed military transport operations - the average speed IIRC was below 20, and the speed LIMIT was something like 30. When you consider that the truck was designed for off-road use, it is important too to understand the military's definition of "road". Most of us would call it a trail. In Vietnam the army had problems with the frames of five ton trucks breaking when operating ON ROAD, due to the rough roads! The military's idea of off-road is NO road, no trail, no path - merely through the woods or fields or swamp or desert.
So, while the M123A1C - and the M35A2, and the M813 are all far from ideal highway cruisers - it is because this is not what they were made for, not because they are a poor design.
When you finish your project I expect it will literally blow the doors off my truck on the highway - but I do not believe yours would survive the testing that the military subjected these trucks to off-road, in the desert, in the swamp, and in the arctic.
If your M123A1C is currently operable as stock, I would urge you to drive it - a good bit, before you tear it down for conversion. A ten ton is not fun to drive, due primarily to its steering. While driving a Freightliner you can relax and "ride" on the open road - such is nto the case for any ten ton I have driven. All of them have to be "driven" every step of the way. Whether the tires, the steering, or whatever, very poor road feel and a lot of hunting. Again, not a design flaw for a vehicle intended to be used primarily off-road - but none the less a fact of life.
And a final bit of advice - install spring safety brakes. The stock brakes are pure air brakes - no air means no brakes. Again - not a design flaw - the idea is if the bullets are flying you did not want to wait for air to build up before driving away. I know a guy who modded his drivetrain, but not the brakes. He twisted out a driveshaft, the end of which swung around and ruptured the air tank. Result - you guessed it - no brakes at all.
Regards,
DD
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