slight bump when coming off the clutch

[kimoyo]

I having a slight issue that I'm trying to figure out. After shifting when I'm coming off the clutch I sometimes get a bump. It doesn't feel like the jolt when coming off the clutch too quick. My instructor says he's off the clutch when he pushes on the gas pedal, he also feels sometimes I'm not running up the rpm's enough before shifting. Any ideas what that bump is? The next time I'm driving I'll try some different approaches but it seems when I start gasing the truck while I'm coming off the clutch I get the smoothest response. Or is my foot just coming off to quick? I feel like I'm already taking forever to get my foot off the clutch and on the gas. Thanks!

[Part Time Dweller]

Who uses the clutch for shifting? Is that some training school thing? :?

[DaveP]

Who uses the clutch for shifting? Is that some training school thing? :?

Have to use the clutch during CDL road test in Alabama

[Roadhog]

Are you feeling the bump in the clutch pedal, or the shifter?

[kimoyo]

I actually got use to power shifting for a few days and then tried to go back clutching and had the worse day. I have a 7 classes until my dmv test so I'll make sure I get it back though.

roadhog - I'm not sure how to tell where the bump is coming from. Its like the truck jumps forward a little or jolts. The jolt is only slight (not a smooth ride) but not as bad as when someone just jerks their foot off the clutch. On Wednesday I'll just ask to do a bunch of clutching on an isolated road. Maybe I'm still not taking my foot off slow enough at the engage point or having a good feeling for exactly where the engage point is. I just spoke with the owner of my school and he also doesn't gas until his foot is off the clutch entirely. I might be imagining my engage point too low and pushing the clutch in to far when shifting.

Thanks for the help so far everyone.

[DaveP]

Sounds like you may be "jamming" it into gear slightly under the correct rpm.

[ben45750]

Does the bump feel like it's coming from the drive-trane? Sometimes you can feel a bump in the drive line when you "stomp" on the throttle instead of smoothly applying the throttle after shifting a gear.

Just as if you quickly tap the throttle at 55-60 in high gear when your empty.

[kimoyo]

DaveP - It could be, thats what my instructor was saying but it happens sometimes when I'm going up to 2000 rpm.

ben45750 - It does feel like that little jolt/knock. So your saying after my first clutch and its in neutral, when I make my second clutch I pushing down to hard and thats causing the bump regardless of how I release the clutch after its in gear. If thats what your saying then that could be it. Because when I was floating sometimes I would do a clutch but it was extremely light because everything was so smooth and I wasn't pushing down on the clutch that far. Then when I went back to double clutching I started messin up and everything went down hill from there.

When you say apply the clutch smooth you still mean quickly though? Is it the speed or depth that is the issue? I try to get the adams familly song in my head and go with a 1,2 speed

Thanks for the help, I really appreciate it.

[TruckerChris]

DaveP - It could be, thats what my instructor was saying but it happens sometimes when I'm going up to 2000 rpm.

ben45750 - It does feel like that little jolt/knock. So your saying after my first clutch and its in neutral, when I make my second clutch I pushing down to hard and thats causing the bump regardless of how I release the clutch after its in gear. If thats what your saying then that could be it. Because when I was floating sometimes I would do a clutch but it was extremely light because everything was so smooth and I wasn't pushing down on the clutch that far. Then when I went back to double clutching I started messin up and everything went down hill from there.

When you say apply the clutch smooth you still mean quickly though? Is it the speed or depth that is the issue? I try to get the adams familly song in my head and go with a 1,2 speed

Thanks for the help, I really appreciate it.

2000rpm? That's a little high to be shifting at whether it's down or up...

[Uturn2001]

My guess is that you are a little too fast getting back on the throttle after a shift.

It sounds like what is happening is that you are not fully off the clutch pedal before giving the truck some juice.

[ben45750]

ben45750 - It does feel like that little jolt/knock. So your saying after my first clutch and its in neutral, when I make my second clutch I pushing down to hard and thats causing the bump regardless of how I release the clutch after its in gear. If thats what your saying then that could be it. Because when I was floating sometimes I would do a clutch but it was extremely light because everything was so smooth and I wasn't pushing down on the clutch that far. Then when I went back to double clutching I started messin up and everything went down hill from there.

When you say apply the clutch smooth you still mean quickly though? Is it the speed or depth that is the issue? I try to get the adams familly song in my head and go with a 1,2 speed

Thanks for the help, I really appreciate it.

It does take a while to get the shifting down. A driver's ego is their worst enemy when it comes to shifting, especially new drivers. You first have to get it out of your head that you have to shift fast. You can take a fast shifter and a smooth shifter and in the end the smoother shifter can get through the gears faster and cleaner than a driver trying to shift as fast as he can. You can also get the truck up to speed faster by shifting smoother than shifting faster.

My advice is to try to slow down on your shifting and try to be smoother. Do you notice a lot of bounce when you shift? The truck bouncing up and down from the torque of the motor? You want to get to the point were your passenger can drink an open cup of coffee without you causing him/her to spill it from your shifting. Try shifting at lower RPM's, both up shifting and down shifting.

One of the best things you can also do while your training is to really pay attention to the trainer when he drives. Sometimes people can learn more by watching others and what they do.

It is also good to learn how to float the gears, but it's best though to double clutch. When ever you take a driving test for a company they will want you to double clutch.

[Jumbo]

DaveP - It could be, thats what my instructor was saying but it happens sometimes when I'm going up to 2000 rpm.

ben45750 - It does feel like that little jolt/knock. So your saying after my first clutch and its in neutral, when I make my second clutch I pushing down to hard and thats causing the bump regardless of how I release the clutch after its in gear. If thats what your saying then that could be it. Because when I was floating sometimes I would do a clutch but it was extremely light because everything was so smooth and I wasn't pushing down on the clutch that far. Then when I went back to double clutching I started messin up and everything went down hill from there.

When you say apply the clutch smooth you still mean quickly though? Is it the speed or depth that is the issue? I try to get the adams familly song in my head and go with a 1,2 speed

Thanks for the help, I really appreciate it.

2000rpm? That's a little high to be shifting at whether it's down or up...

Not if you drive a Mack. Otherwise yes it seems to be a bit high.

[kimoyo]

Thanks everyone for the help!! I have class tomorrow so we'll see how it goes.

We're using a '99 mac, so the shifting rpm is 1800-2000rpm. And I don't notice a lot of bounce when I shift.

What I'll try to different tomorrow is

1. Take my time shifting.
2. Get fully off the clutch before I press on the gas
3. Really get a feel for my engage point. I think this is the most of my problem. Not knowing when I'm actually on/off the clutch.

I didn't mention this before but I switched instructors on Friday and that could have had something to do with my performance. Thinking back over it, the new instructor (hadn't had him for a few weeks) was verbally telling me when to shift which was throwing of my timing. And then he was telling me I had to hurry shifting at certain lights because they change quickly. I had been shifting very well for the past week until I switched to him again. I'll have a conversation with him before I go out also.

Thanks again.

[TruckerChris]

DaveP - It could be, thats what my instructor was saying but it happens sometimes when I'm going up to 2000 rpm.

ben45750 - It does feel like that little jolt/knock. So your saying after my first clutch and its in neutral, when I make my second clutch I pushing down to hard and thats causing the bump regardless of how I release the clutch after its in gear. If thats what your saying then that could be it. Because when I was floating sometimes I would do a clutch but it was extremely light because everything was so smooth and I wasn't pushing down on the clutch that far. Then when I went back to double clutching I started messin up and everything went down hill from there.

When you say apply the clutch smooth you still mean quickly though? Is it the speed or depth that is the issue? I try to get the adams familly song in my head and go with a 1,2 speed

Thanks for the help, I really appreciate it.

2000rpm? That's a little high to be shifting at whether it's down or up...

Not if you drive a Mack. Otherwise yes it seems to be a bit high.

Interesting, I didn't know that... Does that hurt the mpg on a mack or is the redline higher than the other engine manufacturer's?

[kimoyo]

kona911 - I'll take a look tomorrow to see redline but 1800-2000 is definitely the normal shifting range on our '99 mac.


Wanted to say thanks again to everyone. Things went very smoothly today and I was able to apply the advice I had been given. I still need some practice on knowing where the disengage / engage point is. I noticed a few times I was going to far down on the clutch on the second clutch...maybe just moving too fast or really trying to make sure I get the clutch in. We switched to an international '97 so I'm not sure how much better I was but the '99 mac has a newer clutch and clutches better. There were several things I was able to improve,

making sure I was actually double clutching and not single clutching
not going as far down on the clutch
easing off the clutch at the very end a little better
getting the right rpms in
and moving quickly but taking my time also.

I feel a lot better, had 4 days off after Friday's debacle and it was going to my head.

[line_transporter]

I'm not sure how it works on other trucks, but when I drove freightliners and volvos, my trainers told me to keep it b/w approx' 1300 - 1500. Most of the time I just listen to the engine sound to figuer shift points. One thing I never understood is the one inch of free-play of the clutch. You've probably noticed, when you press on the clutch, it goes down about an inch, and makes a little 'click' sound. When I used to double clutch, I'd go beyond that free play, to make the shift. Now I dont use the clutch... but I never did find out what that's for. Any ideas??

[Colts Fan]

I've driven nothing but 10 speeds, Freightliners and Internationals, and it seems that in the low gears anywhere from 1200 to 1500 was a good point to shift and in the high gears 1400 to 1700 was good. Ususally in the high gears I would shift in the 1500 range. Also make sure that you are off the clutch completely before you hit the throttle.

When your done and have your CDL, you'll be happy when you don't have someone watching and you don't use the clutch at all. It's a lot easier.

[gmh]

I'm not sure how it works on other trucks, but when I drove freightliners and volvos, my trainers told me to keep it b/w approx' 1300 - 1500. Most of the time I just listen to the engine sound to figuer shift points. One thing I never understood is the one inch of free-play of the clutch. You've probably noticed, when you press on the clutch, it goes down about an inch, and makes a little 'click' sound. When I used to double clutch, I'd go beyond that free play, to make the shift. Now I dont use the clutch... but I never did find out what that's for. Any ideas??

What's the clutch for, or what's the free play for?

The free play is so that when your foot is off the clutch, the clutch is 100% disengaged. If it were set so that as soon as you touched the pedal the clutch started disengaging, you'd wind up with some slippage depending on changes in weather and temperatures. This'll burn up a clutch pretty quickly.

As far as the MVA wanting you to clutch, just hold your foot in the general area, and pretend you are clutching, but only go into that one inch of free play.

[line_transporter]

I'm not sure how it works on other trucks, but when I drove freightliners and volvos, my trainers told me to keep it b/w approx' 1300 - 1500. Most of the time I just listen to the engine sound to figuer shift points. One thing I never understood is the one inch of free-play of the clutch. You've probably noticed, when you press on the clutch, it goes down about an inch, and makes a little 'click' sound. When I used to double clutch, I'd go beyond that free play, to make the shift. Now I dont use the clutch... but I never did find out what that's for. Any ideas??

What's the clutch for, or what's the free play for?
.

yeah.. after a while of driving, you get into the truck and look down and think "hm, what's that third pedal for?" Then of course you arrive at the Receiver's Dock and you find out you can't float it into reverse.. ahhh, that's what it was for.