From your description, it sounds like an automatic ... I'd bet your torque converter is slipping. Mine will do the same thing when lugging in 6th; I downshift manually and it's smooth as silk. The TCs in these things are only able to handle stock power and very little more.

Mike

 

when pulling a heavy load, like 13-15K, mine shutters a bit when i take off, like 1st gear clutches r slipping. only time it does it.:confused013:

 

I'm on the lowest setting on the smarty I think is 30 hp more.... Would u joints cause a vibration like that? My experience with u joints its usually when you let off the vibrate.... So the TC is going in the tranny? What ever it is it does seem to be getting worse...Is it a big deal to change out the TC?

 

Not sure why you would let it lug? Your results are normal.

 

Hmmm



Not normal, tc going bad, several on this site are having the same problems.

 

Tc.........................

 

welll I think I have narrowed it down to the exhaust vibration at around 1400 rpm when the truck is lugging ...... The exhaust pipe is really light now with the coverter abd dpf off....and I think at certain rpm is shakes....at idle the whole exhaust is shaking....must be what im feeling.....when there is a tail wind its not as bad....same if i run the truck withou my tools its not as bad..... anyone have this same problem? whats the fix? more brackets maybe?

 

I get that same thing some times. I first noticed it while pulling a trailer but now it happens sometimes while going up a gentle hill while the RPMs are low and you what to accelerate to speed up a little. The only way I notice to stop it is to take your foot off the gas pedal and then slowly feather the gas pedal again. I always thought it was the TC but I'm not sure at all.

 

Make use of the T/H mode when towing as well as the EB on. :thumbsup:
Do not lug these things. I make use of the shifter and drop to 5th and even 4th if I need to, to keep the R's above 1500 on hills. On flat ground below 1500 is OK for hiway speeds. Not so nice on grades.

 

What ever you do, do not lug your engine, the tc will hate you for it!

 

by lugging i mean driving 35mph around town........just normal driving....it seems like at a certian rpm it makes the vibration worse...

 

My TC only vibrates when getting on the freeway as I have to slow down on the ones that turn and then straighten out...Only does it when I start to get on it. I have learned to just press the pedal a little harder to pass that point. I did have a slight vibration when I first installed my exhaust but once I had all the sleeves tack welded that stopped. What doesn't make me think it is your exhaust is the fact that you say it "lugs" going up a hill. If it's your TC you will feel it most right under your feet. Good luck, and let us all know what the final outcome is as we all have had these problems:drool2:

 

i get a vibration too sometimes, but only in 6th with the rpm's 1100-1200. the transmission doesnt down shift on its own and i think maybe the converter is still locked. just like the old 6 cyl chevy trucks did with manual tranny and too low of rpm. so i just down shift and always keep prm >1500 . no more problem. if this were the tc i would think more power would make it slip worse. not make it go away. at 1100 rpm you have about 300 # torque. way down on the power band.

 

I got bored and I tried to capture the exhaust vibration on video. It's more like whole drivetrain vibration.

http://www.cumminsforum.com/forum/6-7l-powertrain/285122-engine-vibration-vs-torque-converter-shutter-video.html#post3029661

 

I suspect you guys are feeling engine torsional vibrations. The torque from the engine is not constant, but comes in pulses as the cylinders fire. Torsional vibrations are measured in terms of crankshaft angular displacement, that is, how many degrees the crank position varies from its "ideal" position. Torsional vibrations increase as engine speed drops, and also increase as power increases. For example, the crank angular displacement at 1200 RPM and full load is about 10 times higher than it is at 1800 RPM and 30% load.

So the worst case is low speed, heavy throttle operation (aka lugging). You feel the engine torsional vibrations because they get a lot worse under those conditions. Backing off the throttle, or downshifting to a lower gear (raising the engine RPM) reduces the vibration level. You also feel the vibrations a lot more when the torque converter clutch (TCC) is engaged (in higher gears) because the vibrations are then transmitted directly to the trans and driveline. In lower gears (TCC unlocked) the fluid coupling action of the converter dampens out the torsional vibrations.

If you're concerned that you really have a slipping TCC, your dealer can make a high-speed recording of engine speed and turbine (trans input) speed, using a scan tool. You can then compare the readings to see if you're actually getting TCC slip or not. Some fluctuation (5-10 RPM) in the readings is normal due to speed sensor error (you might see 1450 engine RPM and 1444 turbine RPM). If the "slip" you read is bouncing around between +10 and -10 RPM, you're OK. If you see periods of continuous positive slip (like 15-25 RPM) when the TCC status is Locked, then I'd say you have some TCC slip going on.

But I think in most of your cases, you're likely feeling engine torsionals, so you just need to shift to a lower gear under those conditions.

 

Great Info. Thanks.:thumbsup:

Since I have a manual, and I too sometimes get the vibe when towing, I'd probably go with the above explanation, but I also think there's some axle wrap happening with these long, fairly soft springs. The airbags help a little, but its still there.

 

since we hav a tranny tech in here now......
is it normal for these trucks, when towing somthing heavy, to chugg when u take off from a stop. only does it when i take off. its not overly bad but it makes me wonder if my tranny/TC is starting to go. kinda hard to explain buts its kinda like its pulsating, liek with a manual u hav the clutch in the friction zone and hav parkinsons in ur foot.:confused013:

 

is it normal for these trucks, when towing somthing heavy, to chugg when u take off from a stop. only does it when i take off. its not overly bad but it makes me wonder if my tranny/TC is starting to go. kinda hard to explain buts its kinda like its pulsating, liek with a manual u hav the clutch in the friction zone and hav parkinsons in ur foot.:confused013:

That sounds like launch shudder, which is a propshaft angle / driveline issue rather than a trans / converter problem. When you launch from a stop, your engine speed (with a 68RFE) will normally come up to 2000+ RPM, so you're out of the normal torsional vibration range. There is some torque pulsation from the converter (on any converter), but it's usually not enough to feel or notice.

I have seen complaints of launch shudder with 2-piece driveshafts. To some extent, I'm told it's a "normal" condition, but if your's is bad, have your dealer check the driveline angles. I've heard of this condition being fixed (or at least, greatly reduced) by shimming the driveshaft center bearing position (to adjust the joint angles). Obviously, the angles change depending on how heavily you're loaded. I'm not enough of an expert to advise you any further on this.... hopefully your dealer has a tech with some knowledge / experience who can check your angles and advise you on what to try.

 

Having the engine come up to 2000rpm to get the truck moving seems a bit odd to me.
I kept thinking something was wrong with my transmission or torque converter.
Is the torque converter that loose, or is a combination of that and the transmission?
I thought that with 650 ft-lbs (stock) that this thing would giddy-up a little quicker.
Just seems like the bottom end is lacking.

Scott.

 

I was complaining to Transengineer about my 2007.5 having a loose converter. He said that the 2009 and up truck got a looser converter than I have. So there's your answer.

 

Sweet zombie jesus. So if yours is loose.....

I wonder if a aftermarket torque converter is worth it?
Sometimes I think I should have bought a manual transmission.

Scott.

 

You are talking about lugging....what does your truck do to give you the idea that it is the TC?

 

We have a problem with our Dodge...there is a jerking at 1200 to 1400 rpm's....in 5th,
6th or Drive on the flats..... Has anyone run across this. This does not happen when we are accelerating...we are just holding the speed. Any suggestions as to what might be the cause?

 

Is it 4x4 or what. Lifted?

 

so still battling this annoying vibration....seems to be worse when its colder outside(winter).....pulled the camper this week and seems to be worse at 55-65 mph 70mph goes away......would a torque converter act like that or is it my exhaust shaking bad enough to transmit vibration throught the hanger rubbers?

 

I doubt it is exhaust. Does it always do it in lock up? Always in 5th or 6th gear. if so. I think transengineer my very well be right. I had a jeep liberty diesel that had extreme torsional vibrations. Since it was a 4 cyl it was even worse. I had the converter rebuilt instead of having the dealer put the same on back in on the recall. Once It went into lockup, it would feel like I was running over those groves on the side of the road that wake you up if you veer off to the right. The Whole jeep would vibrate. Turned out that they didn't put the damper back in and once they finally re did the converter with a damper, it went away.
If your having torsional vibrations at a low RPM. Just down shift and it should go away.
Another issue is that if your pulling a hill with a heavy load, you should not be lugging it anyway. The 68rfe is programed to up shift way to early. If I am cruising around town it will up shift until I am at 1100 rpms or lower. This is the fast track to REALLY HIGH EGTS. So I use my paddle and make sure I am in the PEAK TORQUE RANGE of 1700 to 1800 rpms where it will pull all day long. And yes you do have to DRIVE this truck.
I would also recommend getting the new ATS copilot for the 68rfe. If you are having slippage this should solve the problem. It takes over most of the torque management and allows the trans to down shift with out doing the downshif,unlock, gain 100 rpms, the drop 500 rpms when locked up again, problem. It allows the trans to carry a higher line pressure to help with clamping force as well. I love mine, you will notice the difference immediately. Especially running a smarty.
One more Question,,,, what are your egts usually running while this conditions happens.

 

not sure on the egt's dont have the probe in yet....havent pulled much last 6 months...just pulled my trailer a few miles a couple days ago....just never really noticed it when i first got the truck....so torque convertor on it was out?

 

tonight i hauled some rocks for a buddy....box was loaded full...really noticed it unless i shifted so the rpm was over 1600...then it was smooth...

 

Just an FYI, the peak torque on a cummins is 1800 rpm. That is where it like to be when pulling hard, especially on a hill. I think you are experiancing torsional vibrations. Have the Dealer put a new Damper on it, or buy one from FLUID DAMPER. You will notice quite a big difference. And try turning the smarty down and then test it.
And you REALLY really should connect your egt probe. You will be very suprised at how hot it gets. Mine can hit 1450 in no time now, and when it was new and stock, it would reach 1400 and stay there if I towed my 5th wheel in 6th gear,,, ON ANY INCLINE AT ALL. Very important, you should not sustain more that 1350 degrees. You will melt it down. I think if you start driving it using your EGTs as a baseline you will notice it won't have that vibration.

 

so can i install my egt in the egr block off plate from sinister? i tow on SW0 with smarty stock power...thanks for your help....

So a new Dampner and torque convertor .....Is the Dampner hard to change? I have the service manual...