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underpower


hossein
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Hello

I'm 20 and student of mechanical engineering. I've recently registered in this forum. I like this site very much and read some topics because I'm a Mack lover,I'd like to converse with you, I've learned about Mack and other brands from drivers and net especially BMT before.

question : why old Macks are underpower(except E9,E7)?

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Also, depends on what you mean by "old." Prior to 1950's there was no interstate highway system. Much of the Interstate Highway system wasn't completed until the mid to late 1960's. The roads weren't good enough to go much over 55 mph. Trucks were generally geared to pull a heavy load at a modest speed without wasting gas or overheating. A 70 mph or 80 mph truck would be useless and in fact dangerous on the old 2 lane roads.

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Under powered means your not a mack truck driver. To be a mack driver you learn to use what you have and be happy. You learn to take advange of passing on down hills and you learn to start your trip early plus you learn to eat you packed lunch on the road with out stopping and also to you don't stop ever time your buddy wants to cause they have done run ahead of you so they could stop and play around at the truck stop and brag on how shinny their bosses truck is.But at the end of the day you get there and have no trouble sleeping.

But old macks is what we had and that is how we got to were we are now.

Very well put Glenn!

Ron

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Very well put Glenn!

Ron

I agree, and it makes me feel better about my 460 Mack, I love the truck, but it's like Glenn said, and I have no problem falling asleep as soon as my head hits the pillow on that great big thick bed in that beautiful Mack sleeper. With less power and a weaker engine brake, you learn to drive, really drive a truck, up and even more so, down hill.

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Another thing that keeps old macks around is the rear suspension. The camel back is tough and if you get down were the wheels touch the ground and look at the axle housing to the spring attachment you will see that the spring perch is welded to the housing and is a wide perch covering a large area of the axle housing. That guys is what keeps the axle housing from cracking out the housings like other axle housing do. With the camel back springs you have all four wheels on the ground longer than other suspension.The load is spread out more even to the axle housing thru those spring perches also.The rear ends are double reduction also

glenn akers

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  • 4 weeks later...

I think the OP used the word underpowered and was referring to HP rating. I didn't read the whole thread but it is my belief the Mack rates the HP where the rubber meets the road. Other HP is rated at the crankshaft. Detroit, Cat and Cummins don't know what type of driveline you are putting behind their engine, so they can't rate it at the rear wheel. Generally you loose 60-75 HP going thru the trans and diffs, so a 427 Mack is actually around 500 at the crankshaft.

A 427 Mack will show you 427 HP on a dyno. A 425 Cat or 430 Detroit will show you approx 360-375 on a dyno. If you are using an RTLO trans my 500 Detroit shows 460 on the dyno. The "L" in the trans model means it is a LOW inertia trans and doesn't rob as much HP.

Edited by Brandt
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I think the OP used the word underpowered and was referring to HP rating. I didn't read the whole thread but it is my belief the Mack rates the HP where the rubber meets the road. Other HP is rated at the crankshaft. Detroit, Cat and Cummins don't know what type of driveline you are putting behind their engine, so they can't rate it at the rear wheel. Generally you loose 60-75 HP going thru the trans and diffs, so a 427 Mack is actually around 500 at the crankshaft.

A 427 Mack will show you 427 HP on a dyno. A 425 Cat or 430 Detroit will show you approx 360-375 on a dyno. If you are using an RTLO trans my 500 Detroit shows 460 on the dyno. The "L" in the trans model means it is a LOW inertia trans and doesn't rob as much HP.

Low inertia is talking about the spinging mass of gears that that splitter has to snycronize when its shifted.I has the same weight and number of gears turning as any trans so it has noting to do with robbing power.That is also a myth about how mack rates their HP.Its done on a engine dnyno like any engine.Years ago the wheel dnyno would rob about 22% from the engine rating depending on ratios of drive train and rubber plus single or twin screw.Better grease and modern gearing may help that out some.

glenn akers

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  • 1 month later...

Can anyone confirm for me that Mack does in fact rate hp a the wheel. I have a 2013 Pinnacle that's rated at 505 hp. The driver has been complaining of a drop in power since the last time we had the truck into the dealer. Yesterday we had it dyno'd. It was at 420hp. Now the dealer is telling me a 15% drop is normal. I'm headed in to pick the truck up this morning and would appreciate any feed back I can get!

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Hmm, 15-20% % less at the wheels huh? I guess my last E9 truck didn't get the memo, it was rated at 440hp and made 560 at the wheels, don't know why it was so much higher :whistling: .....

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