LUGGING...... lets keep it simple okay? If you push on the go pedal; and the truck doesn't go faster within 5 seconds you are lugging the engine. Lockout the overdrive or if a manual downshift. Any questions

 

Yes, thats normal operation. The TC unlocks before any shift up or down and you see the rpm jump then drop as OD engages. When the trans shifts automatically to OD you don't see as big a jump as the TC lock is just pulsed on-off between the gears.

A tighter converter will get rid of a lot of this slop and rpm jump.

 

Man, excuse me...Thats what I thought these boards were for...questions.

Thanks everyone. I feel better now knowing that my tranny is acting normal.

 

i haven't screwed up the tranny by lugging the motor and i know that it won't hurt the cummins

 

My I-6 Cummins engine gets operated at low under 1600 rpms every chance I get, provided the engine does not have to pull overly hard. My engine rpms are low as a slight or moderate amount of engine power output is required to keep the unit rolling at reduced velocity when there is a strong tail wind on level road, long slight decline in grade, or if the payload is light to moderate on hard level road. I can first detect the change in sound as the engine responds for more power as the pull gets tougher, and then I can downshift before I feel the vibrations in the cab if the engine is laboring and lugging. Those situations existing with low engine rpms at reduced ground velocity present themselves in slow moving heavy traffic, on level narrow rural roads and even on moderate inclines when only the curb weight of the unit is being propelled by the engine. Even though pushing lightly on the accelerator will only increase speed slowly it does not mean the engine is lugging, but pushing the fuel feed to the floor will cause lugging. The engine gets stressed more by stabbing the foot feed to the floor and holding it there in an empty truck on level hard road than it does by pulling a load under conditions where little to moderate amounts of fuel is needed to keep the unit moving at a reduced velocity. I can cause an over legal weight super-b-train unit to stress the engine under deceleration with a Jake Brake without touching the fuel feed except momentarily to aid downshifting the Road Ranger 18 speed tanny to keep the engine rpm on the high side for maximum hold back force, and then only disengage the clutch as the truck stops; wherein, I have not lugged the engine but the stress on the engine is nevertheless substantial. It is when fuel is added to increase velocity of the loaded mass that the engine has to work hard; or at high velocity when stiff wind resistance must be overcome; or when steep grades needs to be ascended. With mechanical injection an idling engine straining for a fraction of a second in front of a manual transmission in low gear when the clutch is directly engaged to lift (start rolling) an overload on hard level road it is momentarily lugging the engine, and that is one reason with computer fuel delivery systems that diesel is automatically added to prevent stalling the engine. If you are lugging an engine you are pushing too hard on the fuel feed to maintain the velocity, or accelerate too quickly over a certain terrain. A truck engine pulling a load should be in a gear to be moderately working all the time, but not lugging. Just because a 5.9 Cummins is running at 2500 rpms it does not mean the engine is not working hard if there is a substantial grade or a stiff head wind while moving at high ground velocity. I can feel and hear an engine that is free wheeling or coasting, loafing or lightly pulling, moderately pulling or cruising, stiffly pulling or working, laboring or lugging. I do not need to down shift just because the engine is working to maintain the reduced velocity at low rpm if little fuel is needed.

 

How do you lug a auto?

 

I put lugging in quotes for a lack of better terms...what was meant was that the rpms were very low at the mph stated and the truck just didnt want to go like I felt it should.

I got all the answers I needed and am again very happy with my truck...Thanks to all who offered the helpful information.

 

Hunting with an auto is the no no...They may have discussed it before I chimed in. If the auto will stay in gear in the mode you have selected it is doing fine. If it gets to hunting in and out a gear you need to lock it in the one it will stay in. I pull in OD with 10,000lbs all the time Tow mode is even better it tends to be a bit more reluctant to shift to the higher gear and will help hold your speed down going downhill. I do undertstand your concern lots of people just put them in D and go for it then complain there auto is no good.

 

I have never owned a HD truck equipped with an automatic transmission nor pulled a load with such an equipped unit far enough to encounter applicable driving conditions; therefore, my experience is limited while trying to hold such a unit's tranny in a higher gear when engine rpms are lower than the set shift down point of the tranny. Our GMC 1500 gasoline powered pickup has an automatic four speed transmission that I attempt to keep from down shifting out of overdrive, while on the other hand it would normally automatically shift down because of decreased ground speed. I am very light footed and have developed a feather like feel on the fuel feed that comes from judging rolling distances in order to have to use the wheel brakes as little as possible. I travel behind the vehicle ahead at a greater distance than most drivers, and I come to a stop much more slowly. I do not speed unnecessarily for the road conditions and traffic congestion. My eyes are analyzing driving conditions a mile ahead of me and I try to anticipate the unexpected or what is out of my vision. Fortunately, the Dodge has a high driver position. When traffic is bumper to bumper I have no choice but to reluctantly keep up with traffic while at the same time not inconveniencing the vehicles behind too much. When I tow a heavy load I do not try to keep up with traffic, I instead try to move the load as safely as possible, and I do not worry about the drivers behind me.

xyzer, your question as to how do you lug an auto can be better stated as how do you keep an automatic from downshifting, because the auto I operate can't be kept in a higher gear if I am normally aggressively firm on the accelerator. On a hard level road with our truck empty it will increase ground speed under slightly firm trottle until the automatic will finally up shift into over drive. I use as little fuel as possible to keep the truck at highway speed. When I am gaining on traffic or am about to enter a speed zone I have already been feathering the fuel and part of the time coasting while slowing down somewhat. The tranny remains in OD even though the ground velocity has become less than needed to keep it in the OD gear. Provided the velocity does not need to be taken too much lower I than can by feathering the fuel prevent the tanny from down shifting out of OD while continuing running at reduced velocity with an engine speed of 1100 rpm.

By not automatically down shifting the tranny it is still able to maintain the forward momentum of the truck because resistance to forward progression is not greater then the limited output from the engine needed to maintain reduced ground speed, due to me limiting the fuel so no acceleration results. The limited fuel needed prevents the engine components from going through excessive stress. That is how an operator results in preventing lugging a low turning engine - limit the fuel if lower velocity is maintained. When more rolling resistance is encountered more fuel is needed to stress the engine for more output, and the tranny down shifts or the operator down shifts a manual transmission.

If the rolling resistance stays constant the velocity of the vehicle can be very slowly increased without the tranny down shifting by feathering an increase in fuel over time, but usually there is not adequate time and I have to let it down shift when more fuel is added. I do not need to run at 1800 rpm if the load resistance does not stress the engine under certain road conditions at lower engine revolutions. Sometimes high rpms just wear out the free wheeling engine unnecessarily and use more fuel than is necessary while not doing any extra work under certain situations. Lugging results if engine components are severely stressed. V8 components are lighter by design and will definitely be detrimentally stressed by hugging an engine. V8 engines have a shorter stroke and will lug at a higher rpm then an I-6 engine.

 

Fay,
My statement was a sarcastic one. My point was I have never been able to lug an auto. Hunting will be the killer of the tranny.

 

Yes, xyzer, I assumed you were politely trying to convey reality that goes something like this, '...you experts' explanations about lugging engines is applicable only when a manual gear box is present, but when an automatic transmission is the equipment, then the engine physically can't be lugged when the tanny automatically down shifts itself.' I really partly do not fully comprehend all information through not being subjected to similar equipment and driving situations.

My reply was to establish there can be a situation were an automatic does not down shift when ground velocity and engine revolutions are lower than the trany's down shift point. I have experienced coasting periodically on long gradual down grades where a light duty automatic will remain in OD at lower engine rpms than is normal, and it does not result in a true lugging situation for the engine to be given a little fuel to keep momentum going when the declining grade lessens somewhat for a short distance.

Having not operated a heavy duty auto tranny, I do not know exactly what hunting entails with regards to the Dodge truck automatics under specific road pulling situations. On certain grades our GMC's automatic will enter the incline in OD, but finds the grade a little too much and it immediately down shifts again to drive. If it up shifts again I put the lever in direct drive to keep the tranny clutch discs from taking repeated wearing abuse. Since my lack of experience does not help my assumption to be definitely factual, I can only assume when I see 'lock out OD' written in a message, that it means just that, placing the manual tranny selector in direct drive.

I have never driven a truck with an Allison automatic transmission, but I would like to learn more about the operation of a heavy duty automatic transmission. I am considering purchasing a 4500 or 5500 in the future once the bugs are worked out of the new trucks. I may consider purchasing a unit equipped with the new Dodge truck automatic that DaimlerChrysler hopes to use to compete with GM. I think the Dodge tanny is called an Asian or something like that. Nevertheless, I still prefer a manual transmission, even though I find the G56 gear spacing too far apart in the lower gears. Second gear ratio if too far from the first gears ration for my liking.

On the engine side, I do not like the high percentage of EGR dumping excessive soot and sulfuric acid into the engine oil, nor the particulate filters on the new 6.7 L Cummins. I am sure happy I purchased my Dodge before the 2007 pollution features were incoporated. I really like my diesel truck if only the ball joints and u-joints could be greased.