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Driving a non-synchromesh transmission is the coordination of the clutch, the throttle, and the shifter.
In order to shift a non-synchromesh transmission, or some times referred to as a “crash box”, the drier must line up 3 things:
1) the road speed
2) the engine speed
3) the gear
If these 3 things do NOT line up, the transmission simply will not shift.
Shifting Pattern 1:34
Range Selector 3:10
13 Speed Transmission 5:03
18 Speed Transmission 6:27
15 Speed Transmission 7:12
Synchronizing the Transmission 8:44
5th Gear – The Happy Gear 10:12
Progressive Shifting 11:44
Double Clutch 16:41
Seat Adjustment 18:04
Uphill | Downhill 22:44
Not a Spectator Sport 24:14
Most transmissions in tractor-trailers in this day-and-age are either a 13- or 18-speed transmission. And all transmissions are essentially a 5-speed “H” pattern.
And progressive shifting was designed to maximized fuel economy on large electronic diesel engines. Progressive shifting indicates that you should bring the revs up approximately 50 rpms and then shift to the next gear. However, when pulling heavy, or shifting uphill, the driver will have to bring the revs up higher to compensate for a drop in road speed.
Finally, the clutch on a non-synchromesh transmission looks like any other clutch, but must be used in a completely different manner than a manual transmission on a car or light truck. There are 4 points along the clutch’s travel path:
2) friction point
3) dead space
4) clutch brake
The clutch brake on a big truck is only used to get the vehicle into a starting gear, whether that is first, reverse or whatever gear the driver start the vehicle in. And to coordinate the speed of the transmission with the the road speed, the driver has to double clutch. Simplistically speaking the driver clutches once to bring the gear selector into neutral and then again to put the transmission in gear.
One of the gears that we like the best is fifth gear. If you lose a gear and you’re trying to recover and find a gear – eighty-five percent of the time the transmission–a 13- or 18-speed transmission–will go into fifth gear. So fifth gear – up here with the range selector up, back to the first slot – fifth gear is your go-to gear. 85% percent of the time the truck will go back into fifth gear and you can carry on. Sometimes it may not be pretty, but you can get it back into fifth gear and go.
In conclusion, shifting theory. All transmissions are basic 5-speed patterns. What allows a 5-speed transmission to become a 10-speed transmission is the range selector. Down for low, up for high. The only time you use the range selector is between fourth and fifth. You’re going from 4th to 5th, pull it up, and shift to fifth.
If you’re going from fifth to fourth, push it down before you come out of fifth and it’ll shift as you go through neutral. And you’ll hear it after you get a bit of practice with it, you’ll be able to hear the transmission click from high range too low range as you’re moving through neutral.
The splitter gives you 13- or 18-speeds. If you get in a 15-speed it’s going to be a blue button. So it’s red, blue, or grey. Red is 13-speed, blue is 15, grey is 18-speed. The clutch is very different than most clutches that you’re going to find on a car or light truck. Top of it’s the freeplay, the friction point, the dead space and then the clutch brake.
And the engine speed is a misnomer – it’s not actually the engine speed that were worried about when we’re shifting the truck. It’s the transmission speed, but we don’t have any way to measure the speed of the transmission gears in a non-synchromesh transmission. So we use the engine’s tachometer.
The clutch pedal has to be out, especially when you’re down shifting and throttling up. Make sure the clutch is out when you’re throttling up. And again the last piece: and this goes for any manual transmission, not just a non-synchromesh – don’t ride the clutch. As soon as you finish shifting the gear, get your foot off that clutch.
Because there’s two plates in there and what happens is if you got your foot on the clutch at all, the two plates start to separate. When the two plates start to separate, they begin to spin against each other and it causes the clutch to wear out. So don’t ride the clutch in any manual transmission vehicle.
The last piece for non-synchromesh transmission: when you’re down shifting, slow down to gear down.
Good luck on your road test!