vibration in drivetrain at low rpm in 4th and 5th gear

bigugly · **Posted:** Wed Nov 26, 2008 11:08 pm

I am getting a vibration that I feel through the seat of my pants when pushing on the go pedal in 4th and 5th gear. Don't feel it all the time. It seems like it occurs when rpm's are at 1700 - 1800 rpm and accelerating or when going up a hill in cruise control and the motor accelerates to maintain speed. It happens some times when shifting into 5th on slow acceleration. Again it is not all the time just some of the time.

Any thoughts on what might be causing this? The tranny is shifting fine and does not seem to be having any issues.

kccrd · **Joined:** Thu Mar 08, 2007 10:35 pm **Posts:** 267

Mine turned out to be a rear u joint I had a greasable joint put in and no problems since.

warp2diesel · **Posted:** Wed Nov 26, 2008 11:30 pm

that turned out to be a harmonic caused by the bumpy road and the trailer.
No vibration on any smooth roads and no vibration with the trailer disconnected.
I would check your U joints, but don't rule out a bad road.

BlackLibertyCRD · **Posted:** Thu Nov 27, 2008 1:31 pm

bigugly wrote:

I am getting a vibration that I feel through the seat of my pants when pushing on the go pedal in 4th and 5th gear. Don't feel it all the time. It seems like it occurs when rpm's are at 1700 - 1800 rpm and accelerating or when going up a hill in cruise control and the motor accelerates to maintain speed. It happens some times when shifting into 5th on slow acceleration. Again it is not all the time just some of the time.

Any thoughts on what might be causing this? The tranny is shifting fine and does not seem to be having any issues.

If it is just a low rpm vibration under load and not all the time, I would think a celtane booster will help like power service. One time I stopped at Iowa 40 truck stop and filled with their premium diesel and I could,nt believe how quiet and smooth the engine was. They were claiming celtane close to 50 and the rest of the country don't come close. Most station you will be lucky to find celtane of 40

journeyjim · **Posted:** Thu Nov 27, 2008 5:34 pm

At what ground speed are you doing when this happens??. Mine the TC will lock up at 63-64 mph and drop the rpms to about 1800, however if speed drops below 60, while going up a grade with out keeping the speed up, I get a shutter until the TC unlocks, and the rpms go back up to about 2000.
These CRDs don't like to be dogged, keep the rpms up and it will run the best.

BlackLibertyCRD · **Posted:** Thu Nov 27, 2008 6:03 pm

journeyjim wrote:

At what ground speed are you doing when this happens??. Mine the TC will lock up at 63-64 mph and drop the rpms to about 1800, however if speed drops below 60, while going up a grade with out keeping the speed up, I get a shutter until the TC unlocks, and the rpms go back up to about 2000.
These CRDs don't like to be dogged, keep the rpms up and it will run the best.

The shutter your experiencing is torque convector slip that will go away when you increase pump (engine) speed. shutter = transmission, vibration = engine

bigugly · **Posted:** Fri Nov 28, 2008 2:30 am

shift to 5th is around 63-64 mph (1800 rpm). A few times it has happened when slowly approaching the 5th gear shift point and it vibrates (kinda feels like hitting the rumble strips on the side of the highway) briefly before shifting into 5th. That does not happen very often and the actual shift is nice and firm.

more often then not when the vibration occurs it is when I am in 5th and have to slow to around 60 and then slowly speed up under load (up hill or pulling my small boat) and then I get the vibration.

again the transmission feels like it shifting ok. I was thinking that maybe motor mounts or u joints on drive shaft.

msilbernagel · **Posted:** Fri Nov 28, 2008 3:06 am

My vote is with the torque-converter slip.. mine does it too. I shift down when it happens (flip OD off) and it stops.

Mark

chadhargis · **Posted:** Fri Nov 28, 2008 10:42 am

I have this problem too.

I took it to the dealer, and they replaced the torque converter, pump, and valve body.

It ran fine for a little while, then it came back. So I had a Suncoast torque converter installed, with the Transgo shift kit. I still have the problem.

So, I figure I'll just live with it by drive around it. If it starts shuddering, I just mash the pedal a little more and it downshifts.

BlackLibertyCRD · **Posted:** Fri Nov 28, 2008 12:38 pm

bigugly wrote:

shift to 5th is around 63-64 mph (1800 rpm). A few times it has happened when slowly approaching the 5th gear shift point and it vibrates (kinda feels like hitting the rumble strips on the side of the highway) briefly before shifting into 5th. That does not happen very often and the actual shift is nice and firm.

more often then not when the vibration occurs it is when I am in 5th and have to slow to around 60 and then slowly speed up under load (up hill or pulling my small boat) and then I get the vibration.

again the transmission feels like it shifting ok. I was thinking that maybe motor mounts or u joints on drive shaft.

If it sounds and feel like your going over rumble strips, it would definitely be torque converter slipping that needs to be upgraded. Small vibration or bumping is fuel problem that can be fixed with a lift pump.

chadhargis · **Posted:** Sat Nov 29, 2008 1:25 am

It's more than the torque converter, but I can't tell you what it is.

I have the exact same issue, and I'm on my second torque converter since I've owned the vehicle. The one in there now is the upgraded Suncoast unit along with with the Transgo shift kit.

So there has to be more to it than the torque converter.

kccrd · **Joined:** Thu Mar 08, 2007 10:35 pm **Posts:** 267

It is the rear U joint!!! Inexpensive fix mine felt like I was driving over rumble strips when I decelerated it was very annoying.

fastRob · **Posted:** Sat Nov 29, 2008 6:02 am

kccrd wrote:

It is the rear U joint!!! Inexpensive fix mine felt like I was driving over rumble strips when I decelerated it was very annoying.

What parts did you use? How did you fix it?

kccrd · **Joined:** Thu Mar 08, 2007 10:35 pm **Posts:** 267

I had the dealer do it, but their part was about $79 and a greasable joint from nappa was $26 my mechanic told me as long as I keep grease in it every oil change it would last much longer just a couple of pumps of the grease gun and that's it you do have to use grease designed for joints such as that. The total for the job was $123 not bad, he also told me he had only replaced rear u joints on the kjs and never a front joint. Mine was completely dry and rusty inside, not good. Hope this helps.

CRDMiller · **Posted:** Sat Nov 29, 2008 12:11 pm

chadhargis;

you say that you have this same shudder/rumble and that you replaced your tc with the suncoast and had the shift kit, and yet you still experience it?

Seems to me like it t'aint your tc, brother.

BlackLibertyCRD · **Posted:** Sat Nov 29, 2008 1:23 pm

CRDMiller wrote:

chadhargis;

you say that you have this same shudder/rumble and that you replaced your tc with the suncoast and had the shift kit, and yet you still experience it?

Seems to me like it t'aint your tc, brother.

Sometimes in this forum we add to the confusion. When I had the bumping an deceleration, I fixed it with lift pump. When I had small vibration I balance tires and that fixed it. Now I have the torque converter slipping like described as going over rumble strip. Well the TQ rumble strip can be bad enough to shake the whole dash if not shifted to a lower gear.

chadhargis · **Posted:** Sun Nov 30, 2008 12:53 am

It it were a u-joint, wouldn't it do it more frequently.

My situation only happens in 4th or 5th gear between 1800 and 2000rpm under load (going up hill, towing, etc) when using light throttle. If I press the pedal down and let it downshift, then it stops.

I've successfully ruled out the TC. I don't think it's a fuel delivery issue either, since I can stomp the pedal to the floor (demand maximum fuel) and everything works perfectly.

The only other thing I haven't looked into is the U-Joint, and that's because I just don't understand how a bad u-joint would cause a condition in only 2 gears between 1800 and 2000 rpm.

kccrd · **Joined:** Thu Mar 08, 2007 10:35 pm **Posts:** 267

Mine only did the vibration at certain times not when I was just going down the highway, a little under acceleration and quite a bit when slowing down until a complete stop. Probably when only under certain kind of stress to the joint we even looked at it up on the rack and twisted the drive shaft back and forth and it felt fine but when the mechanic took it off the shaft and then apart it was all dry and rusty inside, very strange. I now grease it every oil change.

chadhargis · **Posted:** Sun Nov 30, 2008 11:02 am

Well, there's the difference.

My shudder ONLY happens in 4th or 5th gear around 1800 to 2000 rpm or so and only when lightly acclerating (light pedal application).

That's why I've always dismissed it as being a U-joint.

I've always wondered if it's not a function of the TCU. Maybe the TCU isn't programmed to lock up at this low an RPM and it's slipping.

fastRob · **Posted:** Sun Nov 30, 2008 12:01 pm

chadhargis wrote:

Well, there's the difference.

My shudder ONLY happens in 4th or 5th gear around 1800 to 2000 rpm or so and only when lightly acclerating (light pedal application).

That's why I've always dismissed it as being a U-joint.

I've always wondered if it's not a function of the TCU. Maybe the TCU isn't programmed to lock up at this low an RPM and it's slipping.

I will replace the u-joint since the T/C already has been replaced, which was done for towing anyway.

But the Bingo is for the TCM (Transmission Control Module) and the need to firm up the shifts by way of a TCM mod.
Who knows about such things?

vibration in drivetrain at low rpm in 4th and 5th gear

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