Driveline vibration!!! I need help!

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KAMSGTS440

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Hi everyone... the last 18 months I have been restoring my Dart GTS which had been setting since 1991 in my driveway...I've been trying to run down this drive train (I think) vibration the last 10 months... this is a 440 auto car ... engine, rebuilt... A727 tranny rebuilt, brakes rebuilt front to back.. front end rebuilt... drive shaft has new u joints and rebalanced (the drive shaft was 1.5 inches too short...lengthened drive shaft and still have vibration)...new wheels and tires...new motor and tranny mounts. checked tranny to differential angles as suggested by drive shaft company...still had vibration...checked if it was engine related by shifting down into 2nd gear and bringing up engine RPM to same RPM as vibration in 3rd gear(starts at 55 MPH 2800 RPM)...no vibration....this thing feels like a vibration coming from the mid section of the car to the rear end...I've had the differential covers opened up (its a Dana 60) and the differential inspected...needed a pinion shaft seal and 1 axle bearing...still have this vibration...Im at my wits end with this problem and I'm afraid to drive it at freeway speeds with this vibration...dont want to do any damage to the drivetrain...PLEASE I NEED HELP AND OR SUGGESTIONS...:axe:
 
So are you saying that the vibration does not change when you vary the engine RPM and is only related to speed.
 
You say you "lengthened" the shaft. Please explain this. I dearly hope someone did NOT actually lengthen the tube, as opposed to starting over with a second shaft

Generally, play in the trans slip bushing, bent/ worn slip yoke, improperly installed U joints (pins bent in the caps), worn U joints, bent yokes on the shaft, bent tube, out of balance tube, and bent yoke on the differential. Play / worn pinion bearings


How did you check shaft length? You must do this with car weight on wheels, on a flat surface, NOT jacked up with axle weight "hanging."

Shaft could either be too short or too long. Too long-- yoke can bottom out on trans shaft Too short, yoke can be extended off end of splines so far that it doesn't run true

Tell us about how you checked pinion angle? Basically what you want is for the trans output shaft and pinion shaft to be parallel when under acceleration.
 
67Dart273 said:
You say you "lengthened" the shaft. Please explain this. I dearly hope someone did NOT actually lengthen the tube, as opposed to starting over with a second shaft

Generally, play in the trans slip bushing, bent/ worn slip yoke, improperly installed U joints (pins bent in the caps), worn U joints, bent yokes on the shaft, bent tube, out of balance tube, and bent yoke on the differential. Play / worn pinion bearings


How did you check shaft length? You must do this with car weight on wheels, on a flat surface, NOT jacked up with axle weight "hanging."

Shaft could either be too short or too long. Too long-- yoke can bottom out on trans shaft Too short, yoke can be extended off end of splines so far that it doesn't run true

Tell us about how you checked pinion angle? Basically what you want is for the trans output shaft and pinion shaft to be parallel when under acceleration.
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thats what i was thinking...

also make sure the installed the yoke 90* off center from the other... the cross in the yoke for the trans should be 90* from the cross on the pinion yoke
 
805moparkid said:
make sure the installed the yoke 90* off center from the other... the cross in the yoke for the trans should be 90* from the cross on the pinion yoke
Click to expand...

This is not true. the shaft yokes can either be lined up (like rifle sights) or 90* off. What they must NOT be is "somewhere in between"

An example:

resye.3.jpg


and another:

driveshaft-ujnts.jpg
 
make sure your trans mount bolts on the tail shaft are tight.
 
I think we need more info in terms of the vibration... If the car is in nuetral, and you rev it slowly up to 4K rpm, then back to idle... Do you feel a vibration? If yes, it's in the engine/torque convertor. If no, continue:
Drive the car. What speed does the vibration first become evident? Does it start up, get worse, then go away as you slowly speed up? Is it in your seat, or in your steering wheel? Is it constant or does it sort of resonate in your ears (think resonate like the rumble you hear when you drive with the windows open on the highway...)? Last, get the car to the speed of the vibration, then go a little faster, and carefully slip it into nuetral. Does the vibration go away as the engine comes to idle, or does it go away slowly as the car glides and loses speed?
 
demon seed: yes this vibration is speed related...
1970pavalient: no play in the driveshaft
67dart273: this drive shaft was taken to a driveshaft shop...this is all they do...it was lengthened with a new tube rebalanced and new u joints installed, the extended length was determined by them and the measurement was taken with the axle tubes supported with jackstands, pinion angle was measured and was within specs as determiined by the driveshaft company
purplehase:new tires and wheels balance ok
oktire: this vibration is coming from the midpoint to tail end of the car
GUP:new tyranny mounts and new motor mounts but i will check bolts for tightness
moper:this vibration only happens aroun d 55 mph and is not rpm related i feel it in the seat and in the center console and it does get worse...starts at 50-55 gets a little worse arouind 60...it seems as though i can feather the gas pedal and get it to smooth out a little bit... i havnt tried slipping it into neutral at the vibration speed ...i will try that... when I shift down to second gear and at same rpm there is no vibration...also when in neutral sitting in driveway at same rpm... no vibration....

i hope this info helps...i'm at my wits end with this problem
 
KAMSGTS440 said:
demon seed: yes this vibration is speed related...
1970pavalient: no play in the driveshaft
67dart273: this drive shaft was taken to a driveshaft shop...this is all they do...it was lengthened with a new tube rebalanced and new u joints installed, the extended length was determined by them and the measurement was taken with the axle tubes supported with jackstands, pinion angle was measured and was within specs as determiined by the driveshaft company
purplehase:new tires and wheels balance ok
oktire: this vibration is coming from the midpoint to tail end of the car
GUP:new tyranny mounts and new motor mounts but i will check bolts for tightness
moper:this vibration only happens aroun d 55 mph and is not rpm related...shift down to second gear and at same rpm there is no vibration...also when in neutral at same rpm... no vibration....

i hope this infoi helps...i'm at my wits end with this problem
Click to expand...

thats probably your issue... if you can switch the rears to the front and see what happeneds...
 
If the pinion seal is leaking I would look at the rear. The pinion could be twisted or bent. This would cause a leak and a vibration. Take the driveshaft off and have someone spin a wheel and look a the center of the pinion, or put a dial indicator on it and check to see if it is bent. I would say it going to be from the trans back. Steve
 
One more thing I have seen. You mentioned you have a dana. Are you sure you are using the correct u-joint on the rear. The small joint will fit and snug up but will not be centered, Check to see that when the u-joint is put into the yoke on the rear you cannot move it side to side. The clips should fit snug between the ears on the yoke. Steve
 
How do you know the balance on the tires are ok? I bought a new set from a tire dealer.. had a rear vibration at 62 that WOULD NOT GO AWAY. They replaced one of the new tires, they balanced them 4 times... no fix.

Just out of curiousity, I took it to another tire place (new place) and they balanced them. Smooth as silk. Make sure you don't have a bad belt in a tire also.
 
850moparkid:
cant switch front to back small wheel bolt pattern on front but the wheels are new when i put the new wheels on the vibration was still there
oldmanmopar: when i initially inspected the rear end (b4 i noticed the vibration) the pinion was leaking...replaced pinion seal and 1axle seal differential was inspected(visually) and nothing seemed out of the ordinary ...when i lengthned the drive shaft the driveshaft company replaced u jounts and asked me to make sure the u joint snapped into place with no "gaps" around u joint and yoke mating surfaces
rob robinson87: these tires have been to 2 different places to be balanced....when i bought them and again when i bought the new wheels...but i will take it to a place where they can check the tires/wheels dynamically for an imbalance condition
 
I have the same thing with my Duster. It actually did it before I changed the engine and rearend. Still does it with new engine, driveshaft, and Dana 60. the transmission is the only common denominator. It is not a tire, it is in the drive train somewhere. it is not constant, it is speed related, 50 plus and goes in and out in a rythem, 1 second smooth 1 second vibrate, smooth, vibrate, smooth vibrate until I slow down under 50mph. I am stumped. Is this what yours is doing?
 
Did you take the shaft to a reputable shop? Maybe take it to a different driveline shop. I would have the driveshaft checked for run out, if they added to the shaft and did not do this that might be your problem. On the shaft are there a lot of weights? If so, again they may have tried to compensate for the run out. If the addition to the shaft is not straight, well you see where I'm going with this.

I had my shaft shortened and balanced and it was so true that the weight they put on is very small.


Also have you checked your pinion angle?
 
KAMSGTS440 said:
...checked if it was engine related by shifting down into 2nd gear and bringing up engine RPM to same RPM as vibration in 3rd gear(starts at 55 MPH 2800 RPM)...no vibration....:axe:
Click to expand...

That tell me vibration related to driveshaft speed, not engine speed. Have you tried driving 2nd gear till RPM reach 4060 (2800x1.45), I guess it will vibrate @ 4060 RPM as well.

If so, the driveshaft is the problem:

1) the shop did not do good job balance driveshaft. It might show "balanced" at the Balance Machine at lower(higher) speed but it does vibration at certain speed (in this case 2800 @ driveshaft)

2) The driveshaft is too short. The faster you drive the longer distance between end of tailshaft & rear end will be. Therefore the less connect between the tailshaft and the yoke.

Just my 2cent.
 
67Dart273 said:
??? whut ???
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Quote: "The faster you drive the longer distance between end of tailshaft & rear end will be."

Im sorry, I just look at the diagram, I was wrong on this one. The correct is: "the faster you drive the shorter distance between end of tailshaft & rear end "

So your driveshaft either out of balance or too long. If its too long, when driving over 55MPH the driveshaft push the outputshaft forward, this caused vibration.
 
aka474 said:
Quote: "The faster you drive the longer distance between end of tailshaft & rear end will be."

Im sorry, I just look at the diagram, I was wrong on this one. The correct is: "the faster you drive the shorter distance between end of tailshaft & rear end "

So your driveshaft either out of balance or too long. If its too long, when driving over 55MPH the driveshaft push the outputshaft forward, this caused vibration.
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way i ask how you think a metal tube is going to stretch or the rear end is going to creep forward or the trans will get longer?
 
aka474 said:
Quote: "The faster you drive the longer distance between end of tailshaft & rear end will be."

Im sorry, I just look at the diagram, I was wrong on this one. The correct is: "the faster you drive the shorter distance between end of tailshaft & rear end "

So your driveshaft either out of balance or too long. If its too long, when driving over 55MPH the driveshaft push the outputshaft forward, this caused vibration.
Click to expand...

Neither one of these scenarios is going to happen. the rear end or transmission does not change position with speed, the only thing that changes effective driveshaft length is the movement of the rear axle due to bumps and other suspension movement, and what BETTER BE DARN LITTLE that the engine/ trans may move in the mounts.
 
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