Engine/Transmission (1998.5 - 2002) Am I lugging it???

[RJPotts]

I really need to get my gauges put in!

OK, when I'm driving normally I usually keep the RPMs around 2000-2400, that equals 5th at 50mph or so. On occasion, actually on one road that I drive down every day the speed limit is 35 and its in front of a school, a park, a fire station, and a police station so people are always slowing down and stuff. I will normally leave it in 5th and roll along at 35 or so (never slower than 25) not accelerating just pushing the go pedal enough to maintain speed. Should I drop er' down into 4th or 3rd and risk a ticket for noise pollution or am I safe for the 1 mile or so that I do this.

Thanks in advance.

-R. J.

 

[MACHINEST]

45MPH is my low for 5th gear,i usually down shift to 4th saves the brakes,and takes 5 gear off the coast side of the gear ,not good...

 

[RJPotts]

Right on, so keping it around 2000-2500 is in my best interest.

Guess I'll just have to coast by the police station in neutral.

There isn't anything bad about coasting in neutral or with the clutch pushed in for long periods of time or at high speeds is there?

-R. J.

 

[JRichard]

Well, what i can say is that holding the clutch in for long periods of time wears on the throwout bearing very quickly. That said, coasting in neutral would be a better solution in my opinion.



Jake

 

[gonehuntingagain]

5th gear in the 6 speed = 4th gear in the 5 speed.



That being said, you don't need to keep the rpm's above 2000 on a constant basis to avoid lugging. Without a load (constant speed, level ground) you can go as low as 1200 - 1300 rpm. Listen to the engine, it will tell you if you are lugging it by groaning or vibrating (try going 23-25mph in 5th with the 6 speed, you will see what I mean).

Instead of running 2000 rpms and up, try keeping it between 1500 - 1800 and you will see your MPG go way up.

 

[Drewhenry]

shift points

When I run empty I have no problem shifting between 1200-1600

Mileage approx. 18. 5-19. Loaded--2500-2800 mileage approx 17. 3 Numbers figured by hand calc. and trip comp.

 

[NIsaacs]

R. J. Ideling along 35 mph in 5th on level ground under no power is fine. I don't coast in neutral or with the clutch in unless I am stoping. High rpm is not nessessary for any reason with the Cummins, unless you want or need to go fast. I seldom run mine over about 2300 rpm even on a hard dead pull.





"NICK"

 

[obert]

As said, keeping off the coast side of the gear is a good idea, but you also said your not coasting.

It seems the general consensus around here is that "lugging" would be moderate to heavy throttle at or below 1500 rpm. Its not a large bore engine so yes, keep the tach out of the basement, but the ISB has a nice wide power band and my own $. 02 finds shifting at 1900-2100 and landing somewhere in the low teens makes a lovely stroll with an awsome exhaust note and plenty of tourque to do the job... .

 

[RJPotts]

Sounds good, I don't usually coast for any real period of time with the clutch pushed in, usually when I'm coasting at lower speeds and planning on downshifting for a turn or traffic is it. If I'm planing on stopping I'll usually coast for a while in gear to slow down a little then I'll knock it into neutral and use the service brakes the rest of the way. As for the low speed driving I usually try to keep it in 4th until 35 or so (about 2200 rpm) then 5th for speeds up to around 55 mph (2500 rpm) when I'm accelerating then its 6th and lots of noise. Personally, if its not bad I would rather shift at lower rpms (1800-2000) so that I can make a little puff of black smoke as I roll into the next gear. Smoke makes me happy.

Thank you all for your help.

-R. J.

 

[macdaddy]

Can you say lash!!!!!!!!!!!!!!!!!!.

HPCR 56 honey's shout out a nice sound of gear lash when she's lugging, thats my point of reference. I would suspect the 2nd genners don't allow this due to the the 24V rattling it's way to lift pump heaven



Mac

 

[OTRPU]

Don't know nuttin bout the 6 speed, in my auto with 3. 55's and a load it would be luggin it. 35 MPH I'm outta OD. Unloaded seems OK.



Cheers,

Steve J

 

[Boondocker]

I go with what obert said. Using low RPM and lugging are not the same thing. Getting on the throttle at low RPM is lugging. I have no problem going down to any RPM above the idle govenor (around 700 RPM) in any gear below overdrive (6th). If you're going to be at low RPM, you just need to accelerate gently. It doesn't take much peddle for the Cummins to torque its way into the happy zone. For my HO motor, that's between 1600 and 2100 RPM. Low RPM = better MPG. Light throttle application = better MPG. I hate the thought of accelerating hard below 1800 RPM just for my clutch's sake.



I'm not sure what the 'coast side of the gear' issue is about. I'm thinking these NV 5600 transmissions are pretty strong. When I go down hill with my trailer, I gear down, let the exhaust brake do its thing, and stay off the service brakes as much as possible.



Neil

 

[dacook]

Yes, please explain the coast side of the gear? I have been under the impression that it is encouraged to use the engine to slow down a vehicle with a load. aka use of engine brake.

David

 

[WestTN]

I use the 'coast side' of the gears ALL the time. I am trying to find the time to build an electronic circuit that will operate off the rear wheel speed sensor and disable the exhaust brake when not moving. Then I will be using the e-brake and gears at every stop.



It surprises me how so many think these trucks are so delicate. If I couldn't use the engine below 2,000 rpms I would be left with only a 1,400 rpm range of operation.



Lugging refers to older mechanical governor systems injecting WAY to much fuel at wide open throttle at rpm's below the torque peak while loaded so heavy they cannot accelerate. That pounds the bearings out.



These electronically controlled engines are torque limited by the computer (if stock, and mine is) so that 'lugging is physically impossible. Don't believe it? Take a look at the torque 'curve' on one of these and you will see it is totally flat from just off idle to almost maximum RPM's. That is because the computer doesn't permit excessive fuel for any given RPM. My ETH torque peak is 505 lbft. If that isn't going to beat the bearings out at 3,400 or 2,000 then it wont at 1,100 either.



Even in a modified truck you winn not be lugging at 1,100 in 6th gear unlesss the truck is unable to accelerate under heavy throttle.



I'm really surprised that, in spite of having the toughest engine in the market, there are so many prople who are basically afraid to use the engine. I treat this truck the same as I did my 1989 which I put 250,000 miles on and that included idling through low speed zones and then accelearting away without downshifting. That old truck is still a daily driver here in town and still runs like new with closer to 300,000 miles on it. These engines do not need the babying that so many think. If it did, I would be driving something else. And that would be whatever is the toughest in the industry.



I have never used synthetic oil for the simple reason that the documented trucks I have seen in the TDR magazine all seemed to share a common oil. And that oil is Shell Rotella T 15W-40 conventional. If you want to spend money on your truck, spend it on the body and running gear to see if you can keep those running for a million miles.



And that is my $0. 02

 

[obert]

Foot In Mouth?

I rember somthing in drive trains class about wear on the back (coast) side of gear teeth, but I think that was on the ring/pinion set in the rear end. Couldnt have been very important, especialy since most highway application diesels have some sort of engine brake, which do a hell of a lot more than "coast" on the back side of the gears... ... whatever.



As far as lugging the electronic engines, really the concern I suppose is the drivetrain; clutch hubs and springs are not friends of the vibration seen at very low RPM. Worst on the engine its self is probly the low boost/ high heat conditions the develop.



But that was a good way to put it simple WestTN, "smash the throttle+ no acceleration = lugging"