Downshifting

Topic 12141 | Page 1

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Steve J.'s Comment
member avatar

I cant downshift to save my life my instructor yelled at me and kicked me out of the driver seat Im in hell

Daniel B.'s Comment
member avatar
Best Answer!

The easiest way I can explain downshifting is to point out that its all about the RPM's of the engine. It will vary with each transmission slightly but typically the truck will shift out of gear about 300 to 400 RPM higher or lower than it goes into gear, depending on upshifting or downshifting. Let me give you an example:

When going UP the gears most transmissions will go out of gear around 1300 RPM then go into next gear around 1000 RPM. This is known as the RPM spread and most transmissions have about a 300-400 RPM spread between gears. So knowing that to downshift you will need to give a tap on the throttle to bring your RPM's up to get the lower gear. So lets say your in 10th gear and slowing down. Around 45 MPH you will need to shift down to 9th. At that speed your RPM's should be around 900-1000 RPM. So when you need to downshift, while doing your double clutch you should quickly tap the accelerator up to 1300-1400 RPM to get the lower gear. (This is why it's so much easier to "float" gears than double clutch. Floating means you don't use the clutch at all to shift. Its easier on the clutch and much easier to do when you get the hang of it)

When you are giving throttle to bring up the RPM's, it should be a very quick tap on the accelerator and you should only have to push it about 1/4 to 1/2 of the way down. Next time your in the truck, before you start driving practice tapping the accelerator to see how far down you'll need to push it to get the desired 300-400 RPM you'll need to get the lower gear. Also when your going UP the gears pay attention to what RPM you're at when the truck goes into gear. This will give you an idea of the RPM spread of that transmission.

So here's the bottom line. To get the next gear down just tap on the accelerator to bring the engine up to 1300-1400 RPM and you should be able to get the lower gear.

On your CDL test they won't expect you to shift like a pro either. What they do expect is that you don't grind the years all day long. But they won't expect perfection. No one is perfect in your position. Heck, I even asked the same question here on TT that you just asked a long time ago.

Generally, the more miles you drive the better you are at shifting. Remember, when you're solo, you're going to be driving about 60 hours per week. You'll know your truck and what it likes and doesn't like real quickly. So don't sweat it if you're struggling at shifting, it's normal.

I've never had a student who didn't struggle for weeks at downshifting. Its definitely tied with backing as the most difficult thing to learn. This takes time and practice. Keep your head held high, you'll eventually shift like a pro. But what you're going through is totally normal.

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.

OWI:

Operating While Intoxicated

Daniel B.'s Comment
member avatar
Best Answer!

The easiest way I can explain downshifting is to point out that its all about the RPM's of the engine. It will vary with each transmission slightly but typically the truck will shift out of gear about 300 to 400 RPM higher or lower than it goes into gear, depending on upshifting or downshifting. Let me give you an example:

When going UP the gears most transmissions will go out of gear around 1300 RPM then go into next gear around 1000 RPM. This is known as the RPM spread and most transmissions have about a 300-400 RPM spread between gears. So knowing that to downshift you will need to give a tap on the throttle to bring your RPM's up to get the lower gear. So lets say your in 10th gear and slowing down. Around 45 MPH you will need to shift down to 9th. At that speed your RPM's should be around 900-1000 RPM. So when you need to downshift, while doing your double clutch you should quickly tap the accelerator up to 1300-1400 RPM to get the lower gear. (This is why it's so much easier to "float" gears than double clutch. Floating means you don't use the clutch at all to shift. Its easier on the clutch and much easier to do when you get the hang of it)

When you are giving throttle to bring up the RPM's, it should be a very quick tap on the accelerator and you should only have to push it about 1/4 to 1/2 of the way down. Next time your in the truck, before you start driving practice tapping the accelerator to see how far down you'll need to push it to get the desired 300-400 RPM you'll need to get the lower gear. Also when your going UP the gears pay attention to what RPM you're at when the truck goes into gear. This will give you an idea of the RPM spread of that transmission.

So here's the bottom line. To get the next gear down just tap on the accelerator to bring the engine up to 1300-1400 RPM and you should be able to get the lower gear.

On your CDL test they won't expect you to shift like a pro either. What they do expect is that you don't grind the years all day long. But they won't expect perfection. No one is perfect in your position. Heck, I even asked the same question here on TT that you just asked a long time ago.

Generally, the more miles you drive the better you are at shifting. Remember, when you're solo, you're going to be driving about 60 hours per week. You'll know your truck and what it likes and doesn't like real quickly. So don't sweat it if you're struggling at shifting, it's normal.

I've never had a student who didn't struggle for weeks at downshifting. Its definitely tied with backing as the most difficult thing to learn. This takes time and practice. Keep your head held high, you'll eventually shift like a pro. But what you're going through is totally normal.

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.

OWI:

Operating While Intoxicated

Newbie78inpa J.'s Comment
member avatar

I'm not a driver but I watched videos on shifting. A trainer mentioned adding the MPH numbers to give you the best idea of what gear to be in but I'm not exactly sure it applies to downshifting.

For example if you are going 45 4+5 is 9 so you go in 928th gear. 35 mph is 8 so you go in 8th and so on. 55and up is obviously 10th.

Newbie78inpa J.'s Comment
member avatar

I meant 9th gear not 928 gear loll

Really need an edit button on this forum

Robert B. (The Dragon) ye's Comment
member avatar

I meant 9th gear not 928 gear loll

Really need an edit button on this forum

Hahaha, that's awesome. Man oh man would you be tired from shifting.

Adam F.'s Comment
member avatar

Check out these shifting videos. They are really good.

Shifting Part 1
Shifting Part 2
Shifting Part 3

Daniel N.'s Comment
member avatar

Let me say this, Downshifting was my biggest issue, and still to this day, I have some crazy problems with it, but, don't let anyone try to fool you on it. During CDL School, I always thought that you had to downshift gear-by-gear when really, it's just whatever speed you're going. I'm in 10th going 60 and I have to slow down to about 15 mph to make a quick merge or a turn. Just slow down to that speed, clutch it to neutral, give it a small ""vroom"" and clutch it down to 6th. If you instead give it a "vvvrrrroooooooooommmm!!!!" where it comes up to like 1900 rpms, let it drop down to about 15 and then watch it slip right in. The worst thing that can happen when you try to downshift is you grind it a little, but that would kinda tell either to 1) give it a little rpm boost, or 2) look at your speed/rpms and figure out which gear corresponds to that. Trust me, it's not uncommon to be coasting in neutral, lol ...what's such a panic is trying to get it back in gear if you happen to make a turn while in neutral so you don't end up slowing down to a crawl..

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.

OWI:

Operating While Intoxicated

OOS:

When a violation by either a driver or company is confirmed, an out-of-service order removes either the driver or the vehicle from the roadway until the violation is corrected.

Errol V.'s Comment
member avatar

Daniel N reads my mind:

Just slow down to that speed, clutch it to neutral, give it a small ""vroom"" and clutch it down to 6th. If you instead give it a "vvvrrrroooooooooommmm!!

I was reading the OP, and thought about using the the long & short vrrms myself!

BTW, watch that coasting in practice and especially the skills test. GAME OVER if that happens probably more than one time.

Sometimes when a new driver gives it that little " vrrm" kick, it's too much. Hold the shifter where you want it to go letting the gears grind lightly - don't jam them! Let the gears slow down, you may feel it drop into place.

Shiva's Comment
member avatar

I find that in the 2015-16 freightliner cascadia, it downshifts best around 1500 rpm

SouthernJourneyman's Comment
member avatar

I find that in the 2015-16 freightliner cascadia, it downshifts best around 1500 rpm

You sure about that? Cascadia I drove was limited and would barely hit 1500. Should be downshifting closer to 1000-1200 at the most.

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