Trucking 101 Part Two

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Let me introduce myself to y'all.  I'm Peter Crockett AKA The PuterGeek, and on the road I go by Moondog (it's a long story that you probably don't want to hear).

Since Amy is doing a fine job of giving you a broad overview of what we do and how we do it (Trucking 101), I thought I'd explain in greater detail about the equipment.  I'll start by going over our current and (hopefully) last truck.

1999 Kenworth (KW) T600B  Cost $103,000 US.



  Under the hood


Gear ratios

Full gear shifts on flat ground are 400 RPM steps.  Half-gear shifts on flat ground are 200 RPM steps.  You can skip shift (example: go from 5th L to 6th L or 8th H to 7th L) if you're light enough and good enough :-)

Diesel engines are quite different than gasoline engines.  This motor has a working RPM range from 1200 RPM (sustained no longer than 30 seconds) to 2100 RPM (governor limited).  The strong working range is from 1250 RPM to 1750 RPM or only 500 RPM, now you can see why all the gears!  No matter what speed you're going, you can always choose a gear to keep you in the *sweet* spot.

Drive axles

We have Eaton drive axles (rated at 20,000 lbs each) with a gear ratio of 3.55.  When we got this truck I promised Amy I'd try to stay out of trouble, so when we setup the computer controlling the engine I set the maximum speed in cruise to 79 MPH and the maximum speed on the pedal to 85 MPH (many states have a truck speed limit of 75 MPH, and you can usually get away with 4 MPH over).

At 75 MPH in the top hole (8th H) we're doing 1625 RPM, at 85 MPH in the big hole we're doing 1900 RPM.  The *best* fuel economy is achieved by staying below 1575 RPM or 69 MPH.  We almost set the gearing up perfect, I was planning to use 24.5 rubber, which would put us at 79 MPH at 1580 RPM, but that would put our trailer height at 13' 7" which is 1 inch too high <sigh>.

Fuel economy

Last month our true average fuel economy was 6.35 miles per U.S. gallon.  This is figured by writing down the hub at the beginning of the month, subtracting it from the hub at the end of the month, adding in the variance of the speedo (if we drive 100 miles the speedo shows we went 98.6 miles), and dividing by the number of gallons of fuel used.

This number includes idle time (we use about one gallon per hour of idle time.  We must idle for heat, AC, and power), loaded and empty miles, and slow and high speed states.

Some trucks get better MPG, but many get worse, a lot worse!


Ranger provides the trailers we use.  Sometimes we drop-and-hook, instead of loading or unloading.  So in the course of any given month, we might have pulled 4-8 different trailers.

All the trailers we pull are 53 feet in length.  About 90% percent of them have an air-ride suspension...we try very hard to always get an air-ride trailer, in fact, I've been known to refuse a load simply because it's on a spring-ride trailer!  An air-ride trailer contributes greatly to the whole ride of the rig...the better the ride, the better the sleep...the better the sleep, the happier Amy is...and the happier Amy is, the happier I am...'Nuff said!

Some of the trailers we get are in great shape, others aren't.  When we get a shitty trailer we have two what other drivers do which is to ignore the problem, drop it as soon as possible, and let someone else worry about it...or, get it repaired.  You ask why doesn't every driver get trailer repairs done?  Simply because no one pays us for our lost time while waiting for the repair to get done.

Three days ago we dropped and hooked in Memphis, TN loaded for PA.  About 4:30 in the afternoon it was starting to get dark so I turned on all my lights...8 minutes later the circuit breakers popped!  30 seconds later my lights came back on...I thought...Oh shit!  Sure enough, about 7-9 minutes later it happened again.  The only thing that had changed since the night before when nothing was wrong was the fact that we were pulling a different trailer...which meant it was probably the trailer's fault.

The short version is that I stopped at a truckstop around 5:30 and we didn't get out of the shop until midnight!  We couldn't do anything but wait.  Amy went and got us some nuked frozen pizzas for dinner...the rest of the time we sat in the truck and read.

This cost us 6.5 hours of our one paid us for it either. Sure, it's part of the job...BUT, this trailer was fucked-up when we picked it up!  Why should we lose our time when it broke while someone else had it?

There is no good answer to this issue.  What about having our own trailer, you ask?  We drop and hook too much...with our own trailer we wouldn't be able to take those kind of loads.

The simple fact is the driver that had this trailer before us didn't give a shit about the driver that was going to get stuck with this trailer!  This is yet another of the many reasons why Amy and I are ready to get off the road.

Shifting gears

If you have a manual transmission in a shift gears you'd simply come off the throttle as you push in the clutch, shift gears, roll on the throttle as you bring out the clutch.  If you mismatched the road speed, gear, and engine would be no big deal, the weight of the car would simply force the engine RPM up or down as needed and the worst that would happen is you'd feel a slight "lurch".

If the same happened in a big truck (assuming you even got it into gear) you'd drop the drive line!  Consider this...gross weight of a truck is 80,000 lbs.  The torque rating of my engine is 1850 lbs./ft.  I can't even tell you the PSI (pounds per square inch) of my clutch...but it's a lot...and something has to give in a mismatch.  In a chain, the weakest link is the one to give. Well in a big truck... ut of all the components, the drive line is the weakest link.

So what do we do?  The smart drivers learn to RPM shift ( or float the gears).  I don't care what the truck driving schools teach or what the companies say their policy is...ask any old hand, and he'll tell you the clutch is only used for taking off!

RPM shifting is done this way, let's say you're taking off from a stop, so you're accelerating and grabbing gears.  As you get up around 1700 RPM, you gently start pulling back on the shifter with two fingers...1st gear is at the top left corner of a "H" pattern...2nd gear is at the bottom left of the H...when your foot is on the throttle you are either throttle on, or throttle which case the stick won't pull out of gear...but between the two positions you have neutral throttle and that's were the stick will fall out of the gear easily.

As you pull the stick out of gear...the RPM continues to fall. Remember, there is a 400 RPM split between gears on level ground...maybe it'll increase to 430 RPM due to road speed drop between gears. You have to feel for it. So you gently pull the stick towards 2nd the moment that road speed, RPM, and gear speed all'll just suck it right into the hole for you. If you miss, you simply burp the throttle a bit, and try again.

Is it easy to learn?  NOPE?  But consider this...use the clutch and risk losing a drive line if you miss. RPM shift and the worst that'll happen is you'll not get it into a gear and you'll have to start over. Embarrassing?  YEP!  But at least you don't break your truck!  Amy never even learned how to shift gears in a truck with a clutch!  I taught her the right way from the start.

Here's a trucker joke...What's the difference between a housewife and a trucker's wife?  Well, if you blow in a housewife's belly button, she just giggles.  But if you blow in a trucker's wife's belly button, she says "To hell with that, stick it in the big hole and gouge on it!".

Brakes and braking

A car uses hydraulic fluid in it's braking system.  Whether you have some form of power brakes or not, to slow down, all you do is start pressing on the brake pedal until you get the braking force you want.  Whether the car is heavily loaded or not, chances are you'll apply the brakes in the same way to achieve a certain result.

Maybe if you're towing a heavy trailer (without trailer brakes) and you're going down hill, you *might* notice the need to apply more brakes in a given situation than you normally would...but I bet you never thought about it.  Unless you're old enough to remember driving prior to the mid 60's, you probably have never felt "brake fade".

Now let's talk about a big truck. First, a truck uses air instead of hydraulic fluid.  The only reason I can think of as to why this is so is that if a car loses're in trouble. A truck has an air compressor, so it can rebuild it's air supply.  Also, we have to hook and unhook from trailers...which uses air.

The second issue is called brake lag.  Consider how many wheels on a truck have brakes and how many feet of air line there is.  Brake lag on a bobtail is roughly .25 of a second.  Brake lag on a tractor and semi-trailer is roughly .5 of a second.  Remember, in a car, you apply the brakes until they do what you a truck you can't do that due to brake lag. You have to train your foot to know how much pressure equals what.

Now consider this, if I'm deadheading somewhere my rig will only weigh about 34,000 pounds.  But if I'm grossed out, it'll weigh about 80,000 pounds!  Yet the brakes and their abilities are the same.

When we talk about brake application on a big truck, we call it application pressure.  This means that I must teach my right foot that so much pressure on the brake pedal equals so much application pressure (most trucks... if you're lucky...have an air brake application gauge, so you can see if your foot is dumb or not), and...not only that, but I must know how much application pressure I'll need in a given situation with a given gross weight.

Are you confused yet?  Consider this...what if I get new shoes?  What if I usually wear boots (stiff sole), but today I'm wearing sneakers (soft sole)?  The pedal will be totally different to me!  What if my toes are on the brake pedal instead of the ball of my foot?

When Amy first started driving, I made her get a pair of boots and she always had to wear them when she drove. Now she can wear whatever she wants to...but in the beginning it added too much confusion to the learning process.

Picture this...I'm deadheading on a nice dry, sunny day at 60 MPH, the tranny is in the big hole...I'm planning to take the next off-ramp, which gently sweeps up to an over-pass, with a stop sign at the top of the ramp...I'm on flat's what I do...about 100 yards from the ramp I kick off the cruise control, the jake kicks on, I burp it down half a I enter the ramp I apply about 20-25 pounds of brake application pressure...and gently and smoothly ease to a perfect stop at the top of the ramp.

Now, it's the same situation...but with one small difference...I'm grossed out at 80,000 lbs!  That's about 46,000 lbs more than the last time.  Everything else is the same...same truck, trailer, speed, road, off-ramp...only the weight of the rig has changed.  If I wait and kick the cruise off at the same point, drop a half gear, and start braking at the same point...I'll have to use 55-60 pounds of brakes to get it stopped by the time I get to the stop sign!

It won't be a panic stop...but a dog might slide off the bed, something might fall off the top bunk...Amy might wake up...hehe...and it won't be a gentle stop at all...controlled?  Yes!  Safe?  Maybe.  Will it feel too fast...yep!  Let me put it to you this way...if Amy did this while I was sleeping...I'd be out of the bunk before she'd get it stopped, then I'd blow the brakes...and kick her out of the seat (that's what I did when she did something stupid when she was just learning to drive).  It's a rookie mistake and one that *could* kill people. What if an air line blew at that moment?  Or a tire?  Or who knows what?

Do I sound harsh?  The school of hard knocks is a great teacher if you live through it.  There aren't a lot of mistakes that don't have horrible results...and I just described one of the few not so bad ones.  I deal in "what ifs" everyday...some people don't like that about me...bummer!  That's why I'm a great truck driver...because I think about what if this...or what if that.

Keep in mind, if I maintained 55 pounds of brakes (say, going down a hill), they would start fading in about a half of a mile...they'd start to smoke in about a about 1.5 miles I'd have no brakes (remember, we're going down a hill), and I would start accelerating again...and might just die for my stupidity...if I don't kill someone else first.

A truck has about 90-95 pounds of max brake application available to it...that's it...and brake fade is a very real issue...talking about using 55 pounds of brakes in a off-ramp (a very stupid thing to do) the top of the ramp, you'd be able to smell the hot brakes...and this is on a good, completely functional, and properly maintained truck.

Does this help you to see the differences in how a truck brakes compared to a car?


Well that's enough for now.  As we have time and are "in the mood", we'll add more to this section of the website.  Till then "Be good...but if you're not, take plenty of pictures!".

Peter (Moondog) Crockett

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Last Revised: 10/20/2000