Trucking 101:
Brakes:
Red and Yellow knobs are for controlling the parking brakes.
Yellow knob controls the brakes on the truck.
Red knob controls the brakes on the trailer.
When the knobs are pushed in and air is applied the brakes release. Pulled out the brakes are applied. Loose air and the brakes will automaticly be applied.
If driving a truck with no trailer, only the yellow knob is pushed in and the red knob is left out.
When there is a trailer attached to the truck both knobs need to pushed in. If only one knob is pushed in the brakes on either the truck or the trailer will not be released. If the red knob was not pushed in and the truck was driven, the wheels on the trailer would skid and eventually blow out the tires if driven far enough. I have seen that happen in less than a mile. David's trailer had two axles with eight tires. All eight tires would have been locked up if the red knob was not pushed in. To an experienced driver this would be very noticeable. Skid marks from this would be very noticeable as well.
On the truck there are only parking brakes on the rear axles. David's truck had two rear axles and one front axle. David's truck also had what is called a pusher axle, that is an extra axle that is added ahead of the rear two axles. This axle is used to haul extra weight, but does not have parking brakes. Most trucks you see don't have a pusher axle. Some trucks have parking brakes on both the main rear axles and some only have parking brakes on one of the rear axles. Normally if there are only brakes on one rear axle they are on the forward rear axle. If the yellow knob is not pushed in the truck could still be driven and the power from the engine through the drive train would turn the wheels, but it would cause considerable drag. If would be similar to driving a car with the parking brake on. Something noticeable to an experienced driver. Some trucks also have lights on the dash which tell you if the truck parking brake has not been released, and also some trucks will also warn you if the parking brakes are not applied and the key is turned off so the truck doesn't roll away. Trucks are normally always left in neutral when parked.
Sarah mentioned there were skid marks on the exit. I believe this was in a FB post. It was not mentioned if it was known if these were from David's truck or not. If someone that wasn't familiar with driving a truck took off in the truck from at stop at the exit and didn't release the brakes, the trailer would have left skid marks. It would be very obvious if the skid marks were left by a truck traveling down the exit and suddenly stopped or if they were from a truck that was parked and then driven with the parking brakes applied (wheels locked up).
Transmissions:
The most common transmissions found in trucks such as David's are 9, 13 and 18 speed transmissions. There are also 10, super 10 and 15 speeds but those are not as common. Manual truck transmissions haven't really changed any in the past 60+ years as far as gears and shift patterns.
Shifting without using the clutch is called "Floating Gears". Manual transmissions used in large trucks are not synchronized like a manual transmission in a car or pickup truck. There is an input shaft and an output shaft on all transmissions. Input shaft is connected to the engine through the clutch. Output shaft is connected to the drive shaft which turns the differentials gears, which turns the rear wheels. In order to shift gears the input and output shaft speeds need to be matched. Some truck drivers will double clutch, some don't use the clutch at all, while others just push in the clutch and then grind the transmission gears until the shaft speeds match and transmission goes into the next gear. Not very good for the transmission, and they probably won't be a driver for long when the truck needs to have the transmission overhauled and their boss fires them.
To up shift without using the clutch you let off the throttle pedal, pull the transmission into neutral and wait for the engine RPM to decrease, since the clutch is still engaged the input shaft speed will also decrease and then match the speed the next higher gear spinning at the same speed of the output shaft. When those speeds match the transmission is put into the next higher gear and the throttle is pressed.
To down shift you let off the throttle pedal, put the transmission onto neutral, bump the throttle to increase the engine RPM which increased the input shaft speed to match the speed of the next lower gear being spun by the output shaft and the transmission is then shifted in to the next lower gear. The throttle is press and up the hill you go or slow down to a stop.
To shift up through the gears the driver would normally start out in 1st gear, then shift up through 4th gear and then flip the range lever up and shift into 5th gear and then shift up to 8th gear if its a 9 speed transmission.
Shifting a 13 or 18 speed is very much the same but with a 13 speed each of the high range gears can be split. So it would be 1st to 4th, flip lever, 5th low, 5th high, 6th low, 6th high.and so on. On an 18 speed each of the low and high range gears can be split. So 1st low, 1st high, 2nd low, 2nd high and so one.
That's a lot of shifting when driving a 13 and 18 speed. Either of these transmissions can be shifted like a 9 speed not using the high side of each gear and usually the only reason for using all the gears would be when pulling a heavy load or going up a steep hill. Or for the clowns that make Y-tube videos and think they are cool to show themselves shifting up and down through all those gears.
Then there are the clowns that think it's really cool to shift using the Jake Brake (thing that makes a lot of noise and slows the truck down using the engine), which decreases the engine RPM speed faster for quicker up shifting. Those people in my opinion are complete idiots, same with the guys that think it cool to down shift through every gear while using the Jake Brake with straight pipes just so they can hear the sound.
If a person who didn't know how to how to shift the transmission into the high range (flipping lever to use gears 5-8) the maximum speed the truck might be around 30 MPH. That along with what ever time it took to attack David at the exit may explain the lapse in time.
JMO, hope you enjoyed the show.
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