Underpowered trucks

[Morraco]

HOW LITTLE POWER CAN HAVE A TRUCK AND STILL DO THE JOB

I'm aware of the complex relationships among engine power, transmission gears, rear axle gears, GVW, etc, and the impact these have on startability, speed and so on, but I understand experienced truckers consider the engine most important factor in resolving these issues.

I've been doing some research and found out that back in the sixties there were hard-working truckers that could make a truck pull loads grossing up to 50,000 lb with engines as small as 150 hp, of course often at speeds as low as 30 mph, and having to shift every two seconds. The above may be unacceptable nowdays on an interstate road, or possible with heavy traffic in some congested urban area like L.A.

Putting aside a deep spec'in analysis I would like to know real-world opinions on the subject of how little is too little power.

Take for example, a semitrailer combination, 18-wheeler, Cummins 330 ISM 330 hp/1250 lb.ft, grossing about 80,000, 53' dry van, Allison 4500HS six-speed auto, driving between Georgia and Mississippi. Is the above Cummins model too anemic?

Thank you very much for your opinions

[PackRatTDI]

If the drive is relatively flat, 330hp would probably be just barely adequate. JB Hunt used 330hp cummins M11's for years. However you're going to lose some pulling power/MPG due to the lack of gears in the allison. A 6 speed Allison might be fine in a motorcoach, but I'd rather have a wider range of gear selection for an 80,000 lb rig.

Unless there's a specific reason you'd want an Allison.

[person]

Swift runs 370hp and 2:90 rears. And 8 forward gears, if I'm not mistaken.
http://usedtruck.cummins.com/public_...100&marketId=2 your model isn't on there but maybe it can help you some way.[/url]

[roadranger]

...there were hard-working truckers that could make a truck pull loads grossing up to 50,000 lb with engines as small as 150 hp, of course often at speeds as low as 30 mph

They climbed the big hills as slow as 5mph I'm told :shock: .
That allison will rob quite a bit of that power and give you crappy fuel economy - an automated manual transmission is a much better choice. I've driven a 330hp M11 before with a nine speed and it really was a bit of a dog - but it or the ISM can be turned up high enough to be usable. A 410hp Cat I drove was fine as far as power goes so I'd say I need close to 400hp to feel like I don't need to get out and push on the hills :wink: .

[PackRatTDI]

If you want the best of both worlds, go with the ZF Meritor Freedomline. No clutch pedal with those.

[Kranky]

Lose the automatic.

Manual is the only way to go.

And, by today's standards, a 330 HP engine is nowhere near enough.

[Orangetxguy]

Just left a company that runs the M-11 in front of the Roadranger 9 speed and 4.63 differentials. All the trucks east of the Rockies are equipped with that set-up, and cruise at 60, pulling 76 to 80 GVW. Surprising as it may seem, the trucks do a decent job maintaining 53 to 56 pulling the hills up through Kentucky, West Virginia, and so on. The trucks also have an average mpg of 8.6(2006-2007)..so that company isn't likely to change their specs anytime soon. The older road trucks..2000-2004 get upwards of 9.5 MPG. All the OTR trucks are Flat-top T-600's with 60" singlebunks.. Day cabs are all T-800, except on the Westcoast, where they still have Petes, with 600 horse Cummins Signature series.

[Mackman]

Well i drive a 2001 Mack CH with a 350hp mack motor in it with a 10speed. I pull a 6,000 gallon steel tank. @ 80,000 every little hill seems like a big ass mountain. Try to get on the highways is like taking your life into your own hands coming on at 35mph when everyone else is going 75. It does get the job done. But it wouldn't hurt to have Little more.

[Mack2]

Dad has 10 Mack tri axles with EM7 275HP Macks they get the job done and we only have 7 foward gears.

[Mackman]

275 in a tri axle damn i used to run a 87 r model with a 300 and that thing was a dog with only a 5 speed. I guess in N.C. it would not be that bad what is your GVW on a tri axle down there in PA it is 73,280 i think NC is less ain t it???

[GMAN]

If you run Alabama and Mississippi with few hills or mountains, 300 hp or so will do the job. When I first started I had a truck with a 238 Detroit. It got the job done, even with mountains and a heavy load. The difference is that I had to drop to perhaps 3rd gear when one of the newer Detroit series 60's with 430 hp would take the same hill in 7th gear. I do that comparison because I happened to own trucks with those two engines at the same time. If you plan on running a lot of mountains such as out West, you will probably want more horsepower. In the Southeast, you can get by with less horsepower, but may drop more speed on the hills with a heavy load.

[allan5oh]

You guys are right about that m11 getting amazing fuel mileage. Compared to my volvo, it had almost as much power too. One of those 410 hp m11's.

[roadranger]

Hmm... - thought the highest output M11 was the 400hp M11-400e+ ?

[allan5oh]

I thought it was 410, might be 400. I've been known to be wrong before, but it doesn't happen often!

Must be one of them blue moons.

[PackRatTDI]

I thought it was 410, might be 400. I've been known to be wrong before, but it doesn't happen often!

Must be one of them blue moons.

The straight M11 had a top rating of 400. The 410 rating was with the M11 370 ESP (370/410).

So technically you are BOTH correct.

[roadranger]

Yup, found it here: http://www.cummins.com/jp/pages/en/c...B380C4A8F0FC10

[SoCal79]

In the dirt buisness less power is less breakage. I turned down my 400 to 350 a couple of years ago and have been able to keep up ok but on the highway I get spanked by everyone. I think big power on the road helps with fuel economy because you can keep your foot out of it.

[bikerboy]

In the dirt buisness less power is less breakage. I turned down my 400 to 350 a couple of years ago and have been able to keep up ok but on the highway I get spanked by everyone. I think big power on the road helps with fuel economy because you can keep your foot out of it.

The dump truck company i work for also used to think that way. They used to buy trucks with little motors and light rear ends.

Now all they will buy is 500 hp ISX cummins and 18 speed fuller with 46 000 lbs rears, tri-axle dump trucks.

The big motors, use less fuel and are alot easier to drive in deep mud or sand. We don't break driveshafts or rears as often either, now that everything is heavy duty.

[allan5oh]

I think big power on the road helps with fuel economy because you can keep your foot out of it.

Not really true, fuel milege doesn't depend on how much your foot is down.

For example, a 400 hp engine "to the floor" will get the same fuel mileage as a 500 hp at 80% throttle. Now with that 500 hp, if you put it past 80%, you will be getting worse then the 400 hp engine.

[Mack2]

275 in a tri axle damn i used to run a 87 r model with a 300 and that thing was a dog with only a 5 speed. I guess in N.C. it would not be that bad what is your GVW on a tri axle down there in PA it is 73,280 i think NC is less ain t it???

Mackman those trucks will gross 61,050lbs and stay on the eastern side of the state so the 275HP isn't to bad.