Downshifting

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Gary H.'s Comment
member avatar

I know this subject has been beaten like a worn out drum. I was unable to find an answer to a specific question. I take my CDL exam on Tuesday June 26. I have the pre-trip and the backing down pretty well. 27 years as an automotive technician helps. Here is my downshift question. If I am traveling at 45 miles an hour and I would be ready to shift to 9th but I see in the distance 1/4 mile or so up ahead, the light changes to red. Traffic is light and no one really in front of me. Do I down shift one gear at a time? Do I slow down enough to go from 8th to 6th to 4th? If I go one gear at a time do I slow to 35 to shift to 7th or slower? I am confused about downshifting, upshifting I have no problems with. I have to double clutch and have been told a few different ways to do it. Going down one gear, get to 1000 RPM's, clutch in, go to neutral, bump accelerator to 1300-1500 RPM, tap clutch and down shift. Is this right? I want to try and make sure I get this right. Thanks in advance.

Gary

CDL:

Commercial Driver's License (CDL)

A CDL is required to drive any of the following vehicles:

  • Any combination of vehicles with a gross combined weight rating (GCWR) of 26,001 or more pounds, providing the gross vehicle weight rating (GVWR) of the vehicle being towed is in excess of 10,000 pounds.
  • Any single vehicle with a GVWR of 26,001 or more pounds, or any such vehicle towing another not in excess of 10,000 pounds.
  • Any vehicle, regardless of size, designed to transport 16 or more persons, including the driver.
  • Any vehicle required by federal regulations to be placarded while transporting hazardous materials.

Double Clutch:

To engage and then disengage the clutch twice for every gear change.

When double clutching you will push in the clutch, take the gearshift out of gear, release the clutch, press the clutch in again, shift the gearshift into the next gear, then release the clutch.

This is done on standard transmissions which do not have synchronizers in them, like those found in almost all Class A trucks.

Old School's Comment
member avatar

Gary, are you in a truck driving school or training program? Surely they can help you with these minor details.

You can skip gears if you like, but I would recommend downshifting one gear at a time on the test. I wouldn't concentrate on speed of the truck for when to downshift, but rather RPMs or the sound of the engine. You can generally apply the brake to pull it down to about a thousand RPM and then downshift to the next gear.

Usually getting down to 6th gear is enough to ease yourself up to a stop without rolling the truck to far without it being under the control of the transmission. Slow down to where it starts to lug the engine slightly, then push in the clutch and brake until you're stopped.

Old School's Comment
member avatar
Going down one gear, get to 1000 RPM's, clutch in, go to neutral, bump accelerator to 1300-1500 RPM, tap clutch and down shift. Is this right?

Yes, that's a fair explanation of how to do it. That's what I mean by going by the RPM and not the speed. You can use the brake to pull it down to 1,000 RPM and then let off the brake as you start to double clutch. Remember you don't need to push the clutch to the floor. Just tap it down an inch or two.

Double Clutch:

To engage and then disengage the clutch twice for every gear change.

When double clutching you will push in the clutch, take the gearshift out of gear, release the clutch, press the clutch in again, shift the gearshift into the next gear, then release the clutch.

This is done on standard transmissions which do not have synchronizers in them, like those found in almost all Class A trucks.

andhe78's Comment
member avatar

Old School is of course right- brake to 1000, then shift. Couple things I’d add that we needed to keep in mind on the test. We had to downshift to fifth-the tester wanted to see us downshift through the split. And we would not start downshifting till fairly close to the light-if we started slowing down a quarter mile away, we'd get dinged as impeding traffic. Of course it’s done differently in real life, I’ll start slowing the second I’ll see a red light to keep from actually having to start from a stop, but on the test, had to plan on getting up to light fairly quick and stopping. Had to learn how to judge the minimum distance needed to drop from tenth to fifth. We’d also never skip gears on the downshift while testing, they’d rather see you drop a couple a gears in sequence then stop with the brake, rather than skipping gears to get to fifth.

OWI:

Operating While Intoxicated

Turtle's Comment
member avatar

My trainer told me not to skip gears up or down on the test. I also downshifted more on a feel than speed or rpm, but yes it was at around 1000 rpm.

I was told to get it down to 6th when I come to a stop, leaving enough room between myself and the car in front of me for me to drop into 3rd, then creep up to the car in front of me. This would ensure that if I had forgot to drop the splitter and stalled, I'd still have time to do it before the light turned green, thus preventing me from impeding traffic if I stall.

Gary H.'s Comment
member avatar

Old School and andhe78. Thanks for the reply and help. I am in Truck Driving School in Houston. They have gone over several different ways on how to downshift but each instructor seems to have a different way, which I understand. I have been using the tach as my guide to downshifting. One of my instructors told me 1000 rpm for one down and 800 for two down. The two down was more of information for me and not to actually perform on the test. I go today to practice on the range and hopefully some on the road to get this down so I only have to take this test once and not multiple times. Thanks again guys for the help.

Hicks's Comment
member avatar

It's the tachometer that matters, not the speed.

Break to 1000rpm Tap the clutch + shift to neutral Rev to 1400rpm Tap the clutch + shift into gear

The process (for me) takes about a second per gear, so if I'm cruising @45mph in the city in 9th gear I'd start downshifting one gear at a time ~7 seconds from the light (I'll only need 4 seconds to get to 5th and stop, but it's a testing environment and I put on a few more seconds for nerves). Also if there is any traffic between you and the light, just assume that at least 3 cars will pull in front of you and force you to stop earlier than you thought.

A 1/4 mile is 1320 feet... but if you were going 55mph you shold be able to stop in just under 600 feet. Yeah, I know you should break smoothly and what-not but that is way far out... and then you'll feel like a chump if you're creeping up to the light at 15mph in 5th gear and probably overreving your engine. Personally? I used telephone poles as markes for where I should start breaking. And if somebody cuts you off (and they will) stay in gear, break until the engine lugs ~500rpm then clutch + break to an emergency stop.

Now you can totally stop in 7th gear in an emergency, but you CANNOT, CANNOT, CANNOT stop without being in gear. #autofail.

And once you stop: CHECK THAT YOUR SPLITTER IS DOWN, clutch + shift to neutral, clutch + shift to 3ed or 4th gear!

Good luck on your test!

TommyGun's Comment
member avatar

Ah downshifting. What a weird feeling is it to manually rev the engine to slow down.

Advice from guys above work great, but I would rev a bit higher, say 1550-1600 rpm on your test. Why? Because you might be a little slow double clutching. Revving a bit higher will ensure you dont miss.

But thats my two cents.

When you get out on the road, you'll eventually get good to shift according to the sound of the engine.

Don't worry about skipping or floating.

Double Clutch:

To engage and then disengage the clutch twice for every gear change.

When double clutching you will push in the clutch, take the gearshift out of gear, release the clutch, press the clutch in again, shift the gearshift into the next gear, then release the clutch.

This is done on standard transmissions which do not have synchronizers in them, like those found in almost all Class A trucks.

Double Clutching:

To engage and then disengage the clutch twice for every gear change.

When double clutching you will push in the clutch, take the gearshift out of gear, release the clutch, press the clutch in again, shift the gearshift into the next gear, then release the clutch.

This is done on standard transmissions which do not have synchronizers in them, like those found in almost all Class A trucks.

Yuuyo Y.'s Comment
member avatar

This is the first time I've seen anyone mention not to skip gears on the test. Not even at school have I heard that. I find 8 to 6 to 4 to be really really handy coming to stop signs/lights since normal speed around the streets will be 8th gear anyways.

G-Town's Comment
member avatar

This is the first time I've seen anyone mention not to skip gears on the test. Not even at school have I heard that. I find 8 to 6 to 4 to be really really handy coming to stop signs/lights since normal speed around the streets will be 8th gear anyways.

Three of us are suggesting the same exact thing, don't skip gears during the test.

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