Do you Rev to upshift or down shift?
Discussion in 'Questions From New Drivers' started by zoekatya, Feb 28, 2014.
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Driving a Mack with a 10 manual sometimes I rev downshifting. But if you listen carefully, you will find that perfect rev your gearbox loves. And don't even use the clutch, just to take off.
Unloaded? 2nd low loaded? 1st low. Don't want to put stress for free on the truck. Easy on the go pedal! -
Rev match on the downshifts. If I'm empty I'll start in 2nd or 3rd and skip up to the top. I take all the gears if I'm close to full.
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I have no scientific basis for this, but i think starting off in a higher gear places unneccesary wear on the clutch. Its just my opinion. I have an 18 speed and i start in hi one, and skip up. Just seems easier on the clutch.
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I rev to down shift only and start out in third then shift to 5th, 7th, 8th.... My general rule is out at 1700 rpm and in at 1100 rpm whenever shifting.
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IMHO the art of learning how to downshift on a steep grade is an essential tool for any trucker. There's no way I'm going to continue on mile after mile of a steep downgrade snub braking frequently and potentially starting a fire in the tandems or losing my brakes. Every time I go down a familiar hill it's a little different, largely depending on how heavy I'm pulling. I take a calculated guess what gear and jake setting will hold me on the hill, based on my weight, then see if it will hold. If that particular gear in high jake won't hold then I need to downshift.
As soon as I determine I'm in a gear too high for a grade I immediately apply brakes to bring my rpm's down to around 800, disengage the jake (it's easier to shift without it engaged), then catch the next gear down at around 1200-1300 rpm and reengage the jake. By bringing the rpm's down so low it's easier to take time to get that next gear, I am slightly raising the rpm's as I get into that next gear down and can keep "following it up" to 1500ish if I need to. If for any reason I'm unsuccessful getting into the gear then I get back on the brakes and bring the speed down again and go for the gear again, but this is an extremely rare event (I think the last time I had to brake twice for a downshift was well over a year ago in a truck I was unfamiliar with).
The trick is to use your brakes to slow down for that downshift EARLY in a descent, while the brakes are still cool and you have plenty of air pressure. Don't wait to do this if you've been trying to control your speed with your brakes for several miles without success. Brake early, get into a gear that works, select the jake setting that will hold the hill without snub braking or very minimal snub braking, and enjoy a cup of coffee as you slowly crawl down the hill.
I think trying to NOT downshift on a downgrade is something that is taught by a lot of schools and companies, and I think it sets up a lot of younger/newer drivers for bad situations trying to control their descent by overusing their brakes.
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