Here I am

Engine/Transmission (1998.5 - 2002) Engine Lugging & Automatic Transmission

Attention: TDR Forum Junkies
To the point: Click this link and check out the Front Page News story(ies) where we are tracking the introduction of the 2025 Ram HD trucks.

Thanks, TDR Staff
Status
Not open for further replies.
transmission / Engine Question. While driving down the freeway in semi heavy traffic in OD I'm turning approx 1400 RPM in OD. Would this be lugging the engine? I've read if going under 50 MPH not to use OD but on the freeway @ roughly 50 thats where my tach is at.

Any suggestions?



Clay
 
I've heard that its hard on the transmission if you're in OD lockup with RPM's less than 1625 so I usually allow it to shift into 4th at 60 and lock out OD when slowing below 55.
 
Lugging is anytime you add fuel (pedal) and the engine cannot increase speed. Regardless of RPM, load, or conditions, that is the ONLY definition of lugging the engine. You can lug the engine at 2500 RPM, just the same as 1000 RPM.



As for the transmission, as long as you do not use a lot of power at low RPM the transmission will be fine. If you use the torque available to you at low RPM you can damage the transmission. How fast and how bad you damage it depends on how much power you have. I do a lot of driving at 1100-1500 RPM locked in OD. Trans has 110K miles on it now, and has had way more power put to it then it is supposed to be able to handle.



Keep the boost down and accelerate gently at low RPM and you will be fine. If you are going to nail it unlock and let the RPM come up, then hammer the crap out of it if you want.
 
Keep the boost down and accelerate gently at low RPM and you will be fine. If you are going to nail it unlock and let the RPM come up, then hammer the crap out of it if you want.



1. When your smoking the tailgaters, let the turbo slow down then lay down on it and listen for the turbo, when it just begins to spool let off:D



2. If your in a low RPM situation like this in lockup, tap... ... . repeat, tap the brake and it will unlock the converter..... I use this allot!



3. The problem at low RPM is low line pressure but most of all LOW pump speed, don't let anyone fool you all of our auto's have low pump speed at low RPM... no way to cure that except a bigger pump... ... . hence 48 RE in the 2004's.



Jim
 
Since my 'DTT' rebuilt transmission, I lock-out overdrive below 45 mph's because the truck seems to be lugging if I don't. Plus, when I 'punch' it, it flat out gets it on!

Bob in Sacramento
 
Lugging

If I remember right, the DodgeRam.com website says that lugging occurs when the engine speed is below torque peak, the vehicle at WOT, and the engine speed will not increase because of load. As for the transmission, low RPM equates to low pressure, which allows slipping to occur in the torque converter. All of this information is gained from various websites, like this one :)



Ronco
 
"Keep the boost down and accelerate gently at low RPM and you will be fine. If you are going to nail it unlock and let the RPM come up, then hammer the crap out of it if you want. "



Pretty good advice. Unlock'er and wrap it up!!!



I think everybody knows and even a few people agree that the TC clutch is the weak link in the autos, but a lot of people don't realize how weak the rest of the thing is if you don't keep the rpm's and correspondingly the line pressures up. Faster is better for your slushbox. The faster you spin the converter, the more efficient the coupling becomes. Of course it's the most efficient with the TC clutch locked up, unless/until it slips, and thay's pretty much a guarantee.
 
Last edited:
Originally posted by Big_Daddy_T

Arent there inexpensive ways to defeat the low line pressure?



Yup, You could turn up the line pressure by adjusting the screw on the valve body, which can lead to bad shifting characteristics if turned up too much. BD makes the pressure lock that brings the line pressures up to full when the TC locks up.



Ron
 
Why is it that I usually see the same or lower temps (read in the pan) locked up than unlocked. I can have OD locked out and read 175 degrees, then unlock OD and the temps will go down to a steady 150, even at 1. 5-1. 75k rpm. The same thing with stopped and put in neutral (I don't see the temps going down).



I think I've heard that the dipstick sensor may pickup some ambient eng heat (especially a low speed or stop & go situations). I hoping this is why I'm not seeing cooler temps with unlocked.
 
As you stated it could be your sending unit. the best place for the sending unit is in the hot line running to the heat exchanger. the second best is in the transmission pan.



Your temps should run cooler in lockup. the reason is more fluid is going to the heat exchanger and then on to the cooler located in front of the radiator.



Ron
 
Originally posted by ronsram1999

Your temps should run cooler in lockup. the reason is more fluid is going to the heat exchanger and then on to the cooler located in front of the radiator.



Ron



Ron,



Help me out with some Auto Trans 101 please, I think I"m confused. When you say lock up are you just talking about when the TC engages (regarless of whether we're talking about in 3rd or OD) or do you mean when the truck is running in OD?



I thought I had a handle on this whole subject until I got a temp guage and despite what I read here all the time about it being better to run with OD off (due to higher line pressure/better cooling because of the associated higher RPMs pumping more fluid) I generally see lower pan temps running in OD vice 3rd at the same MPH.









Are you saying that If the trans will run cooler locked up than what's the point of locking her out of OD?
 
Yes, when the tc lockup clutch engages. The temperatures should run cooler in 3rd locked and in OD locked. Out of lockup in any gear should have higher temperature readings.



Most people lock out OD when towing to keep the line pressure up in the transmission. The line pressure is regulated by how much you are pushing the throttle down, So most will run in 3rd with their peddle 3/4 of the way to the floor to keep line pressure up. On modified transmission this is not necessary because they are modified to flow more oil in all gears and especially in OD. Stock or Modified transmission I see no point in locking out OD if you are unloaded, unless you are traveling in traffic that never goes over (example only) 45 MPH, then I would lock it out of OD just to help keep temps down and make it easier on the stock transmission.



Ron
 
Status
Not open for further replies.
Back
Top