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18 wheelers

Discussion in 'The Lounge' started by protechk5, Jul 6, 2005.

  1. protechk5

    protechk5 1/2 ton status

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    Ok got a few questions about 18 wheelers, what sizes and types of engines do most have, inline 6 diesels right?? How much tq and hp? How many gears and what type of transmissions, and also dont you have to double clutch or something??? I heard one guy said that he only uses the clutch when he starts and stops??
    Thanks
     
  2. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    My best friend was OTR , he could answer better than I .
    But basically they put out less than 600 horsepower , many under 500 horsepower .

    They do however put out OVER 1000 foot pounds of torque :D

    This one puts out 1850 foot pounds :bow:

    [​IMG]
     
  3. jarheadk5

    jarheadk5 1/2 ton status

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    Most are inline-6 turbocharged diesels. BIG turbocharger. Not sure about HP, but the bigger engines are laying down 2000+ ft/lbs TQ, at around 1800-2000rpm, for a million miles. IIRC, the Kenworth T2000 was named that partially because one of the available engines put down 2k ft/lbs TQ, and it was the first OTR truck to have such a powerful engine available from the factory.

    The transmission is almost always a multiple-reduction type, usually with a "front box" and "back box". In the Fuller Roadranger transmissions, the front box is shifted with the actual shifter, and usually has 5 forward gears and 1 reverse. There is one mainshaft and two countershafts. The back box is where the extra reduction or OD comes from, and is shifted by air, with a switch integrated with the shifter knob. Roadranger back boxes have either 2 or 3 gears, depending on the specific model. Some examples: direct and overdrive; low and direct; low, direct, OD; double-low, low, direct. This gives possible gear counts of 10 fwd-2 rev, all the way to 18 fwd-3 rev. There are some new, automatically-shifted Roadrangers out there whose control computers coordinate with the engine computer to shift without the clutch, but as I understand it, they're not real popular. There are also some older oddball RR's out there with torque converters instead of manual clutches, but they're really rare. Weight for a Roadranger with an iron case and bellhousing ranges anywhere from nearly 600lbs for a FRO-series 10-speed, to over 900lbs for a RTLO-18908LL (an 8-speed double-low unit rated for 1850 ft/lbs input TQ. Popular for dump trucks, concrete trucks, and heavy-hauling trucks.).

    Mack transmissions are another ball game - they have aluminum cases :eek1: , one mainshaft, and three countershafts. Most have a front box with an integral bellhousing, a mid box, and a back box. Older ones have 2 or 3 shift levers; newer ones have air shift for the mid and back boxes. A Mack is a massive transmission, and most weigh around 1000lbs.

    None of the heavy transmissions are synchronized, so double-clutching is usually required. But with big diesels having such narrow powerbands, it's fairly easy for a driver to figure out that if he shifts at 1800rpm, and the next gear drops him to 1400rpm, he can do it by feel in the shifter, without the clutch. If it's done right, there's nearly no wear in the trans. A guy I worked with in the truck transmission shop I worked in had a buddy who was an owner-operator. 800K miles on his truck, on the original clutch and transmission. Used the clutch to start and stop, shifted by feel the rest of the time.
     
  4. 4GUNZ4X4Z

    4GUNZ4X4Z 1/2 ton status

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    My personal semi is pretty norm for the industry. It has a 12.7 detriot (500hp/1550lbs), a rockwell 10spd, and 3.73rears. I bought 3 more recently and they all have 500 detriots, 2 have rockwell 10spds, 1 a meritor 10spd, and all have 3.58 rears. As far as "double clutching" the last time I ever did that was when I took my road test at the DMV. I only use the clutch to stop and start.
     
    Last edited: Jul 7, 2005
  5. divorced

    divorced 3/4 ton status

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    As already stated they have turbo charged 6 cylinder engines. Most are between 470 to 600 HP and 1450 to 1650 FT LBS of torque. A real popular Detroit engine is 12.7 liters, most others are similar in size. Transmissions are mostly 9, 10, 13, 15 and 18 speeds, with the 10 speed being the most common. Rear end ratios are normally around 3.55 and 3.73. The tires are about 42" tall. At 65 mph most trucks will run between 1400 and 1600 RPM with a redline around 1800 to 2000 rpm. 6.5 miles per gallon is close to average. I only use the clutch to get moving and when I need to stop; all shifting is done without the clutch. If the clutch is used to shift it is called "double clutching", but few people do this. Here is what we see in our mirrors, which isn't much. This is a pic looking down the side of a 53' long trailer at a GraveDigger wannabe truck that was passing me.
     
    Last edited: Feb 15, 2006
  6. jarheadk5

    jarheadk5 1/2 ton status

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    That 10-speed Rock is a nice tranny. I rebuilt a couple of them before I left that job; they're almost a carbon-copy of a Roadranger, but Rockwell made a couple nice internal improvements. I understand they shift like butter (for what they are, anyway... :D ).
     
  7. ronnny

    ronnny 1/2 ton status

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    alot of busses run detroit v6s and they are a few v8 but you don't want them as much because of the natural way that the inline has a longer stroke so get more torqe than in a v configuration. That's why buses and boats will run alot of v configured motors is not having the need for the torque. There are a few 7 speed trucks out there put the ones i know that drove them said they weren't worth a.
     

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