RPM And Upshifting Question

Topic 12607 | Page 1

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Ruminator's Comment
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Here the situation. I'm driving a 2009 freightliner with 10 speed manual. First time driving this truck. I'm hauling like 20,000 lbs max load weight, I believe, it's a "training" tractor trailer. Ok, I just turned onto a road from a stop in 4th gear at 10 mph. (Actually started off in 2nd and shifted to 3rd then 4th before I turned) This is the speed and gear I'm being told to make turns in. I'm also told that 5th equals 15mph and 6th equals 20mph, etc.. After I straighten out I need to eventually get the truck to the the speed limit of 45 and I'm on a level road.. With my foot on the throttle in 4th I look down and my Speed is 15mph which is the speed I need to be in to go to 5th but I see that my rpms are at 2000 and climbing...not understanding why that is; I decide to quickly shift to 5th and immediately hit the throttle again so I can quickly get to 20mph and my next shift point (6th)..However my Rpms only fell to like 1700 I think because they're back above 2000 almost instantly and I'm not even at 20mph yet....I'm at like 17...so I just go ahead and shift to 6th. Foot quickly back on the throttle. Same problem, my rpms instantly rise above 2000 again but now my speed has only crept up to like 19/20...

What do I do?

My next shift point is 7th/25mph.... But I'm not close to 25mph because I'm still at 20 but yet my rpms are really high at 2000 and climbing? If I let off the throttle to let my rpms fall then my speed also falls and I don't want to do that Right? Because I need to get with the flow of traffic because 20 in a 45 isn't really safe and I have no reason to be traveling that slow...

It doesn't seem like I can get the engine to normal and can barely get the truck going in a timely manner..

What was I doing wrong?

Or is this truck flawed? Or is this carrier wrong that 5th = 15, 6th=20, I was taught in school that it's 5th = 10, 6th = 15.

Robert B. (The Dragon) ye's Comment
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Personally, I've never been impressed with the whole, this gear for this speed theory. Simply use the 10-15 rule on the tach. 15 for your up shifts, 10 for your down. At least while you're learning, it will keep you consistent and get you used to also listening to the engine rpm. 2000 rpm and higher is too much, you're out of the power band and just wasting fuel, not to mention making your shifts much harder.

Scott O.'s Comment
member avatar

Here the situation. I'm driving a 2009 freightliner with 10 speed manual. First time driving this truck. I'm hauling like 20,000 lbs max load weight, I believe, it's a "training" tractor trailer. Ok, I just turned onto a road from a stop in 4th gear at 10 mph. (Actually started off in 2nd and shifted to 3rd then 4th before I turned) This is the speed and gear I'm being told to make turns in. I'm also told that 5th equals 15mph and 6th equals 20mph, etc.. After I straighten out I need to eventually get the truck to the the speed limit of 45 and I'm on a level road.. With my foot on the throttle in 4th I look down and my Speed is 15mph which is the speed I need to be in to go to 5th but I see that my rpms are at 2000 and climbing...not understanding why that is; I decide to quickly shift to 5th and immediately hit the throttle again so I can quickly get to 20mph and my next shift point (6th)..However my Rpms only fell to like 1700 I think because they're back above 2000 almost instantly and I'm not even at 20mph yet....I'm at like 17...so I just go ahead and shift to 6th. Foot quickly back on the throttle. Same problem, my rpms instantly rise above 2000 again but now my speed has only crept up to like 19/20...

What do I do?

My next shift point is 7th/25mph.... But I'm not close to 25mph because I'm still at 20 but yet my rpms are really high at 2000 and climbing? If I let off the throttle to let my rpms fall then my speed also falls and I don't want to do that Right? Because I need to get with the flow of traffic because 20 in a 45 isn't really safe and I have no reason to be traveling that slow...

It doesn't seem like I can get the engine to normal and can barely get the truck going in a timely manner..

What was I doing wrong?

Or is this truck flawed? Or is this carrier wrong that 5th = 15, 6th=20, I was taught in school that it's 5th = 10, 6th = 15.

1+5 =6th 2+5=7 3+5=8 and so on... Should be shifting at or around 1500 I thought course I'm not driving now and can't seem to remember lol

Old School's Comment
member avatar

I agree with Robert. There's way too many variables involved to break it down to a formula. Depending on what the rear end gear ratio is in that truck you may never get up to 40 mph until you get it all the way up into 10th gear.

Ruminator's Comment
member avatar

I know that I should be upshifting at 1500-1600 rpms but at the time I was watching my tandem clear the turn and I believe I was also on the throttle a little when it did make the turn and I was moving straight . That's when I saw the tach at about 2000 and climbing... So I thought a shift to 5th would put me back into 1100-1500 range but it didn't...and when the same thing happened and I went to 6th it also didn't "correct" ....it didn't drop in gear smooth at 2000 but it didn't grind either ...

Tandem:

Tandem Axles

A set of axles spaced close together, legally defined as more than 40 and less than 96 inches apart by the USDOT. Drivers tend to refer to the tandem axles on their trailer as just "tandems". You might hear a driver say, "I'm 400 pounds overweight on my tandems", referring to his trailer tandems, not his tractor tandems. Tractor tandems are generally just referred to as "drives" which is short for "drive axles".

murderspolywog's Comment
member avatar

Sounds like to me the clutch might be going out. At least that's what happens to my car when the clutch went out on it. Rpms would go way up before the speed did. My truck won't let me get above 1800 rpms it just stops. I agree with Robert about the 10 and 15.

Decanuck's Comment
member avatar

If you tried shifting the truck I drive now at 1500 with a full load on the truck drops to 1100-1200 and the engine laughs at you and you have to shift again..... it needs to run around 1750 before you shift and likes to be around 1400 to really pull...... the previous truck I was in was a cat and if you had it over 1500 it would be screaming at you to shift it..... they are all different but I would wonder if like the previous poster said maybe you have a problem with the truck mechanics themselves

murderspolywog's Comment
member avatar

I know that I should be upshifting at 1500-1600 rpms but at the time I was watching my tandem clear the turn and I believe I was also on the throttle a little when it did make the turn and I was moving straight . That's when I saw the tach at about 2000 and climbing... So I thought a shift to 5th would put me back into 1100-1500 range but it didn't...and when the same thing happened and I went to 6th it also didn't "correct" ....it didn't drop in gear smooth at 2000 but it didn't grind either ...

Ok I see what happens you ran to 2000 in 4th and did not realize it. So you shifted to 5th and then to 6th. Trying to correct the high rpms am I right? What I would have done is skiped 5th and gone to 6th at that point. You are progressively shifting up and acclerating at the same time your rpms will be high intell you get your speed down for there gear you are in or get into a higher gear for the speed. Dose that make sense?

Tandem:

Tandem Axles

A set of axles spaced close together, legally defined as more than 40 and less than 96 inches apart by the USDOT. Drivers tend to refer to the tandem axles on their trailer as just "tandems". You might hear a driver say, "I'm 400 pounds overweight on my tandems", referring to his trailer tandems, not his tractor tandems. Tractor tandems are generally just referred to as "drives" which is short for "drive axles".

murderspolywog's Comment
member avatar

If you tried shifting the truck I drive now at 1500 with a full load on the truck drops to 1100-1200 and the engine laughs at you and you have to shift again..... it needs to run around 1750 before you shift and likes to be around 1400 to really pull...... the previous truck I was in was a cat and if you had it over 1500 it would be screaming at you to shift it..... they are all different but I would wonder if like the previous poster said maybe you have a problem with the truck mechanics themselves

I used to do that but it was only because I was slow in shifting. Once I got my temppo up. I could shift and only loose 300 rpms keeping the truck in the power band. I have also noticed Detroit's like to shift higher. In the 1700 rpms on the dd15 engine. Most big truck engines Detroit, cummins, I don't know about the cat. But they develop best power at 1300 to 1500 rpms. That's were the hp/t curves meet meet and the engine is happy. That's why it likes to pull at 1400 rpms.

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.

Decanuck's Comment
member avatar

Its actually at 450 mercedes ..... very little low end torque really nothing until about 1400 pulls good then..... like I said they are all different.... the cat I was driving before would be screaming at you at 1500+

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