Engine/Transmission (1994 - 1998) Lugging a Manual

[pete97]

Is it bad to Lug a manual transmission. I know it was bad to lug the auto. Now that I have converted to a 5spd, is it bad to Lug it? Thanks Pete

 

[TPCDrafting]

I keep my rpm's up when towing, in most cases start out in 1st gear and always keep 5th gear at or above 1700 rpm which is right about 55 mph. Drive yours how you like, that's just how mine is driven.

 

[MLee]

Pete97;

lugging helps to contibute to the 5th gear nut failure, if this is where your doing the lugging below 1700 rpm's. As TPC points out, use the lower gears, higher rpm. Just don't lug it, worst thing that can be done to a diesel engine. RUN IT LIKE YOU STOLE IT

Marv. .

 

[EKlem]

Lugging does equal damage to the actual engine in both an auto or stick but most autos won't let you do it. Lugging puts more pressure on the engine because you need more power per piston stroke so you put in a lot more fuel. I don't have personal experience with looking at a 5. 9 that has been lugged but a lot of the marine diesels that I work with have major bearing problems from having the wrong gear ratio and prop combination that leads to lugging. The worst part of all is that you get worse mileage if you truly are lugging. If you have a pyro, you can tell when you are lugging it because you won't be going anywhere fast and you will have some pretty high egt's.



As far as the transmission is concerned, a lot of people feel that lugging contributes to the 5 gear nut falling off. It does put more wear on the transmission but I personally worry about the engine more.

 

[pete97]

Thanks for the replys. I don't lug it on purpose but sometimes around here with the stop and go traffic it is hard not to. I have the updated shaft and 5th gear nut. What is the optimum RPM range for fuel economy? Thanks Pete

 

[EKlem]

There is actually a graph from cummins that correlates fuel economy/power to rpm at wot. The optimum is right at torque peak. However, as you need less power, the sweet spot drops in rpm some. If you think about it, idle is the most efficient for zero power output and torque peak is the most efficient for wot so everything else falls somewhere in between. The more power you need, the higher the rpm you should run. If you have a pyro, that will help you a lot with efficiency.



I know what you mean about sometimes not being able to help lugging. There are big enough gaps in the gearing that sometimes when upshifting, you have to lug for a second or two to get the rpms up.

 

[Forrest Nearing]

GSK = being able to wind out the gears = no more lugging!

 

[arthr31]

can we define lugging? Too low RPMs (aka wrong gear), or as I've also heard, too low RPMs and RPMs won't increase with any amount of throttle given?



Also, when do ppl shift? After reading this thread, I'm maybe too sensitive to how I'm driving.



In my 5-speed, it generally goes like this: 1st gear 5-10mph; 2nd gear 10-20mph; 3rd gear 20-30; 4th 30-45 or 50; 5th gear 50+



I have the GSK, but don't wind it up all the time, that's too much power for around town driving... Also, I've read that these engines are low RPM engines... So, with that said, does it hurt any to cruise around at like 1200 RPM? Most of my driving is in 4th and that is usually like at 1800...



thx

 

[chazj]

I "Copied and Pasted" the following from the website Dodgeram.org and (I think) Geno's website.



Q: Can I lug my Cummins engine?



From: Josh Berman <j. e. berman@metc. cummins.com>

Subject: Operating below torque peak RPM



The Cummins B-Series O&M (Operation & Maintenance) Manual says:



"Cummins engines are designed to operate successfully at FULL THROTTLE under transient conditions down to peak torque engine speed (edit by D Fritz: The torque peak occurs at 1600 RPM for the B series engine used in the Ram; the torque peak occurs at speeds as low as 1100 rpm for some larger engines). This is consistent with recommended driving practices for good fuel economy. Excessive FULL THROTTLE operation below peak torque RPM will shorten engine life to overhaul, can cause serious engine damage, and is considered engine abuse. "



So you're right, we don't recommend FULL THROTTLE operation below peak torque RPM. However, just after the first caution, the manual says:



"Operation of the engine below peak torque RPM can occur during gear shifting due to the difference of ratios between transmission gears, but engine operation must not be sustained more than 1 minute at FULL THROTTLE below peak torque RPM. "



So basically you've got 60 seconds of continuous FULL THROTTLE operation below torque peak RPM; if the engine can't handle the load and RPMs don't increase to above peak torque RPM, downshift to raise engine speed.



However, operation of the engine at less than FULL THROTTLE at speeds below torque peak RPM is ABSOLUTELY OK.



I hope this helps clarify the issue,



-Josh Berman

----------------------------------------------------------------------

Joshua Berman MidRange Service Cummins Engine Company

-- email address removed -- Cummins Homepage: www.cummins.com



Some Rules Of Thumb:



Engine "lugging" is defined as operating under a load great enough that engine speed can not increase at wide open throttle (assuming that the governor is not cutting the throttle).



Generally, you can cruise around town in the Ram at 1100 rpm with no trouble, but you should avoid using much throttle at such low engine speeds.



Hope this helps.

 

[Forrest Nearing]

also, if you turn up the engine to put out more fuel and make more power sooner, it'll hurt even more...



I generally shift at about 2500-3000rpm... My engine breathes well w/ the ported head and big turbine, so the engine feels more like a gasser as long as I don't give it much throttle. It just feels right. I usually cruise at 1900-2000 unless I'm on the highway and going faster than that

 

[Shadrach]

Generally speaking with a diesel if you put you foot down and it doesn't rev up you are in too low a gear ( lugging it ). According to Cummins the best rpm for economy with a 12valve are 1700-2000 and for power 2000-2700. For a 24valve, economy 1900-2300 and power 2400-3200. Shadrach

 

[pete97]

Thanks. That is alot of usefull information. I have a #10 plate and I never lug it an give it full throttle. Just driving around in western Pa with traffic and all of the up and down hills, I tend to run in 4th gear alot and when pulling a hill the RPM's will usually run about 1500 or so. From the info it looks like this is ok. Just wanted to be safe instead of sorry. Also I do not have GSK and I can run the RPM's up to 3000 in 3rd gear. I didn't think I would be able to but I can. I haven't tried the other gears yet. Thanks for all of the info. Pete

 

[BigPapa]

Generally speaking with a diesel if you put you foot down and it doesn't rev up you are in too low a gear ( lugging it ).

Should read "... you are in too HIGH a gear (lugging it). "



Scott