This basic skill needs taught to those entering today’s industry.
By John Fowler, CSP, CMSP
Drilling can be a great career for those who enjoy a challenge and like physical outside work. It can also take you to places that not many people ever get to see such as large surface mines, urban areas, and even nuclear power plants.
However, it is becoming more difficult to find people to work in the drilling industry who have what used to be considered a basic skill—like how to drive a manual transmission.
Most companies will gladly train you how to shift and drive, but if you already possess these skills, it will make you that much more valuable on a drilling or pump rig. In fact, obtaining a commercial driver’s license (CDL) will usually put your name at the top of the list when a company is deciding who to hire.
Automatic transmissions for heavy trucks seem to be gaining in popularity, but they are only just beginning to appear in the drilling and pump industry. It is safe to assume most of the heavy commercial trucks in our industry are still manuals.
There are two types of manual transmissions you may have to drive on the job: a light truck manual transmission and a heavy commercial truck transmission. Even though both transmissions may look similar, there are some key differences you must understand. Failure to change gears correctly is not only a safety concern but can create large repair bills down the road.
Inside a typical manual transmission, you will find an input and output shaft, gears, and in a light truck’s transmission, a synchromesh device often called synchros that assists with shifting.
When driving, we want the engine operating within its power band which is a set range of rotations per minute (RPMs). The demands of driving, however, means sometimes the vehicle needs more speed or torque and that is where the transmission and gear ratios come in.
Gear ratios allow the engine to multiply torque when it is needed without increasing the engine RPMs out of the power band. A simple way of thinking about this concept is the more rotations it takes for the engine to turn the rear wheels, the more torque that is being produced.
For example, let’s take the ZF S6-650 6-speed manual transmission used on the older Power Stroke Ford pickups. That transmission has the following gear ratios:
- First gear 5.79:1
- Second gear 3.30:1
- Third gear 2.10:1
- Fourth gear 1.31:1
- Fifth gear 1.00:1
- Sixth gear 0.72:1
This means in first gear it takes 5.79 rotations from the input shaft coming from the engine to produce one (1) rotation coming out of the transmission. This is fine because in first gear you are not concerned with speed, but only with getting the vehicle moving. This gear would easily get you moving with a heavy load, but only at a few miles an hour.
In sixth gear, though, it takes less than one rotation (0.72) of the input shaft to produce one (1) rotation out from the transmission. This is ideal when you are driving 65 mph with all the momentum of the vehicle behind you.
Light Truck Manual Transmission
A light truck’s manual transmission is much more straightforward to shift than a heavy commercial truck. When the clutch is depressed all the way to the floor, the engine power is disengaged, and that combined with the synchros allows a smooth shift to the selected gear. You can shift up and down easily without having to worry about matching engine RPMs.
There are a couple of bad habits that people can sometimes get into when using a manual transmission—riding the clutch and dropping or dumping the clutch.
Riding the clutch is when you leave your foot on the clutch pedal while you’re driving. This will apply just enough pressure to keep the clutch from fully engaging and will lead to a premature failure of the clutch. So, when you are driving and not about to shift, make sure your foot is off the clutch pedal.
Dropping or dumping the clutch is when you are in gear, and instead of slowly lifting your foot and allowing the clutch to slowly engage, you take your foot off the clutch and allow it to snap back into position and violently engage with the engine. This leads to unnecessary damage.
Heavy Commercial Truck Transmission
A heavy commercial truck’s transmission may look like a light truck’s manual transmission, but looks are deceiving. Most large commercial vehicles with manual transmissions do not have synchros and have more gears than what you find in a light truck.
Large trucks can have 13 or more gears and typically have a high-gear and low-gear range. Shifting this type of transmission is completely different than shifting a light truck, and if you try to shift it the same way, there is the potential for damage.
The clutch in this type of heavy commercial vehicle has two positions:
- All the way to the floor, which is how you engage the clutch brake
- One-half to three-fourths of the way down, which is the position for shifting.
When starting from a standstill, you must push the clutch all the way to the floor and engage the clutch brake before shifting into first gear.
Once the truck is moving, the clutch brake is no longer needed and all the shifting from then on requires the clutch to only be depressed one-half to three-fourths of the way to the floor. If you push the clutch all the way to the floor and try to shift once the truck is moving, the clutch brake will engage, and you will not shift.
You have to remember these trucks do not have synchros to assist with shifting, so it is critical you match the right gear with the right speed, or you will grind gears and not shift.
Each truck is different, and it will take some practice before you master a new transmission. Some people are taught to float the gears, which means changing gears without using the clutch. While this is common, no matter how smooth you think you are at floating the gears, it is easier on the transmission to double clutch. And you will need to know how to double clutch if you decide to get a CDL.
Keep in mind, if you take your CDL test using a truck with an automatic transmission, your license will restrict you to automatic transmission trucks. For this reason, I recommend testing in a manual transmission truck because you will then be able to drive manual and automatic transmission trucks on public roads.
And remember, a commercial vehicle is a vehicle with a registered or physical weight in excess of 10,000 pounds. This can be a one-ton pickup or even a three-quarter-ton pickup pulling a trailer. If you exceed 10,000 pounds, you may not need a CDL Class A or B, but you will need a CDL physical and a DOT vehicle inspection.
How Does Double Clutching Work?
If you are shifting from first gear to second gear, once the RPMs have reached the point where you want to shift, press the clutch one-half to three-fourths of the way to the floor. Take the truck out of first gear, release the clutch, press the clutch again one-half to three-fourths of the way to floor, put the truck in second gear, and slowly release the clutch.
Keep in mind trucks have a shifting rhythm and shift at only one speed, so don’t think you can shift faster if you are in a hurry because all you will hear is the grinding of gears.
Start out in the low-range gears and then switch to high-range gears and repeat the shifting pattern until you reach your desired speed. There is a selector on the knob to go from low range to high range and it is important to always switch or pre-select the selector before you shift. If you switch the selector during the shift, you may cause problems in the transmission.
When you are shifting, there is a technique to be aware of called progressive shifting. This is when you try to keep the RPMs as low as possible to reduce fuel consumption. The actual RPMs you should use vary from engine to engine, but typically each gear is shifted 50-100 RPMs higher than the previous gear. For example, shift into second gear at 900 RPMs, third gear at 1000 RPMs, etc.
The real test of your shifting skill will come when you are stopped on a hill with a heavy load. It is very easy to roll backwards into a vehicle behind you or damage the drive train in this situation.
You must use your right foot to hold the brake, place the truck into gear, and then slowly start letting up on the clutch. When you hear the engine start to bog down and you can tell the clutch is starting to engage, release the brake and slowly release the clutch. This will prevent the truck from rolling backwards and allow for a smooth start.
To really get the feel of a truck’s transmission, you need to practice downshifting as this will really teach you how a truck shifts. In order to downshift correctly, you must increase the RPMs before shifting into the next lower gear. So press on the clutch one-half to three-fourths of the way, take the truck out of gear, release the clutch, rev the engine to the top of the power band, press the clutch one-half to three-fourths of the way down, shift into next lower gear, and release the clutch. Each truck has its own shifting rhythm and once you figure that out, shifting will be easy.
No one was born with the ability to shift or drive a truck, so if you are not familiar with how to do this, remind yourself that everyone you are working with had to be taught how to do it. Don’t be afraid to ask for help. Your supervisor will be much happier to show you the correct procedure than to deal with the aftermath of a damaged clutch or worse.
John Fowler, CSP, CMSP, is a safety manager for National Exploration, Wells & Pumps in Gilbert, Arizona,
and has taught workshops at NGWA’s Groundwater Week. He can be reached at email@example.com.