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pulsating driveline vibration? #2651966
05/04/19 05:58 PM
05/04/19 05:58 PM
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middle Tennessee
mopower440 Offline OP
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1972 dart swinger, 440/727, 3.23 geared clutch type 8 3/4 rear. I just got finished rebuilding the front end and doing the K-H disk swap. Finally got that all done and now noticed i have this pulsating vibration in the driveline somewhere.. Almost like swearving over onto the rumble strips back and forth..not quite that bad but... It had been fine and sits most of the time in the garage so i dont know where this came from all the sudden. I jacked it up and ran it through the gears on the jackstands and it still did it. I crawled under the car and grabbed the drive shaft and shook it and there doesnt seem to be any play in the u-joints..Im stumped. Like i said, its been fine and seemed to just develop out of now where.. any ideas?

Re: pulsating driveline vibration? [Re: mopower440] #2651972
05/04/19 06:13 PM
05/04/19 06:13 PM
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Grand Prairie,Texas
stumpy Offline
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Rear tire or driveshaft. Remove the drive shaft from the rear yoke and reinstall it 180* form where it was. Then run it again

Re: pulsating driveline vibration? [Re: stumpy] #2651977
05/04/19 06:37 PM
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My mysterious pulsating drive line vibration was from a cracked flex plate. Took me forever to figure it out.

Re: pulsating driveline vibration? [Re: stumpy] #2651987
05/04/19 07:18 PM
05/04/19 07:18 PM
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mopower440 Offline OP
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Originally Posted by stumpy
Rear tire or driveshaft. Remove the drive shaft from the rear yoke and reinstall it 180* form where it was. Then run it again


Not the tires because it still does it without the tires bolted up..Why would it just start doing this out of the blue though?

Re: pulsating driveline vibration? [Re: mopars4ever] #2651988
05/04/19 07:18 PM
05/04/19 07:18 PM
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Usual checkover involves:

Neutral, Park, in gear, and which gear
Rolling at idle or engine RPM
Close look at balancer, pulleys, even fan blades
Any sound like a growl (wheel bearing for example)
Do a nut-and-bolt on things including mounts

May have been a very minor deal previously that finally became noticeable.

Re: pulsating driveline vibration? [Re: topside] #2652077
05/05/19 05:50 AM
05/05/19 05:50 AM
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My Dart has this also has a bit of in and out 'phasing' rumble when cruising at the same speed at lower speeds.

But I know the front u-joint has some little play and this started occuring when I reversed the way u-joint was installed recently. It also had some visible wear on the crossjoint itself. I will replace it with a new one.
I also know a header tube is very close to a torsion bar and it will sometimes vibrate slightly against it, but that's not the cause of the driveline-'phasing' I'm feeling at times.

Re: pulsating driveline vibration? [Re: BigBlockMopar] #2652079
05/05/19 06:03 AM
05/05/19 06:03 AM
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Valencia, España
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I'm on same deal since EVER... My drive line goes something like RRRRRRrrrrrrrrrrrrrrrrrRRRRRRRRRrrrrrrrrrrrrrrrrrRRRRRRRRrrrrrrrrrrrrrRRRRRRRrrrrrrrrr and I can feel it just right down the center console. It begins to BE there from around 60 mph INCREASING up to the point the car becomes "undriveable" around 110-120 mph. At that speed it's not anymoure pulsating but constant and hard. My interiror rearview mirror shakes with it Things that have changed allong the years at diff stages ( not chasing the vibration but making upgrades on car )

-TC
-Full rear axle: from open to SG, from 3.23 to 3.55, 1 axle, axle housing.
-Drums
-Wheels
-Crossjoints ( including change the rear yoke on driveshaft from the 7260 to 7290 )
-Crankshaft / stroking my 400 )
-Flywheel.


and vibration is still there

Just left to check:

-Tranny master rebuilt kit just in case tail shaft housing bushings are worn
-driveshaft itself ( althought once has being told it was good )
-instal the tranny tailshaft housing counterweight.

Last edited by NachoRT74; 05/05/19 06:06 AM.

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Re: pulsating driveline vibration? [Re: NachoRT74] #2652137
05/05/19 09:56 AM
05/05/19 09:56 AM
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Lincoln Nebraska
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What Topside said, I would rev it in neutral & if good I would take out the driveshaft & checkout the joints for smooth back & forth movement


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Re: pulsating driveline vibration? [Re: RapidRobert] #2652267
05/05/19 01:57 PM
05/05/19 01:57 PM
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have either of you had the drive shafts checked for straightness and balance ? We have had more than one get bent by exhaust x pipes or crossover tubes when the rear end was allowed to hang.

Not being able to feel it makes it difficult to diagnose.
Tire balance, flat spots, separated belt ? Have them checked by a GOOD tire shop.
My next check with a vibration like your describing is the drive shaft. Once that is known to be OK onto u joint angles, pinion bearings. One can check the RE housing to see if it feels excessively warm.

A thought in closing: When a problem mysteriously appears think back to what you have changed / done. Many times you'll find the answer

Keep us posted beer

Re: pulsating driveline vibration? [Re: BigBlockMopar] #2652292
05/05/19 03:09 PM
05/05/19 03:09 PM
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Lincoln Nebraska
RapidRobert Offline
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Quote
My Dart has this also has a bit of in and out 'phasing' rumble when cruising at the same speed at lower speeds.
I had that once & it was the yoke was not far enough into the trans. I got the right shaft that was 1" longer & that took care of it.


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Re: pulsating driveline vibration? [Re: RapidRobert] #2652344
05/05/19 06:03 PM
05/05/19 06:03 PM
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mopower440 Offline OP
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Update: Today i pulled the driveshaft only to find the u-joints are absolutely fine! Still just as smooth as the day i had them put in, no binding at all. I was hoping thats all it would be but no such luck. So i spun the pinion on the rear end and in turn, it spun the wheels, both forward (suregrip) and no noise. I had my grandson spin the wheels while i laid under the car where the rear end is and no unusual noise. So, i put the driveshaft back in, installed it 180 degrees off from where it was just to see if that would help. After i got the shaft bolted back in, i had my grandson spin the rear wheels again while i laid under the driveshaft and i could here a boom...boom..boom...boom coming from the tailshaft of the trans. So i scooted myself up under the tailshaft and had him keep spinning the wheels and sure enough, its coming from the tailshaft and i could slightly feel it in the tailshaft..So, im assuming this is where the problem is. Obviously he couldnt spin the wheels very fast but enough to make the pulsating boom and i guess when its spinning fast, it causes the bad vibration. I fired it up on the jackstands again and it seems to have kind of a slight vibration going all the time, but the pulsating bad vibration comes in about 40-45 MPH and way worse in 3rd gear than second..I can run it up to 45 in 2nd and its not near as bad as when it shifts into 3rd and at that same speed. I dont know much about transmissions so this really has me upset! when i bought this transmission, it was freshly rebuilt and when i got it, my friend tore into it to verify and it had been for sure. I bet i have not put 1000 miles on it since then, which has been around 2002 or so. It shifts fine and all, no slippage or anything. The ONLY thing i saw questionable when i pulled the driveshaft out was the shiny area on the front of the driveshaft that slides into the the transmission had some pitting going on and IF the tailshaft bearings used that shiny part of the driveshaft that slides into the trans as the inner race, then it would make sense as to this vibration being from the pitting..but i dont think its made like that..?

Re: pulsating driveline vibration? [Re: mopower440] #2652469
05/06/19 08:11 AM
05/06/19 08:11 AM
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RapidRobert Offline
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Progress. If there is enough yoke engagement into the trans then sounds like it is time to pull the ext housing & R&R the bushing.


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Re: pulsating driveline vibration? [Re: mopower440] #2652556
05/06/19 11:25 AM
05/06/19 11:25 AM
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Can you set up some device to check for run out on the drive shaft or drive shaft yoke?
If so do that to see if the output shaft is bent or not wrench scope
If you can't get help to do that up twocents


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Re: pulsating driveline vibration? [Re: Cab_Burge] #2652594
05/06/19 12:36 PM
05/06/19 12:36 PM
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If you find the trans output bushing to be the problem, it seems logical to me that something caused the damage, which would lead me to question the yoke & driveshaft.
Yoke engagement & spline condition, shaft imbalance, shaft runout.
Reading through this thread again, I just recalled something:
In '73 I ordered a Z28 and after it arrived, drove it a week or so before I noticed a rhythmic vibration.
Took it to my local dealer and after a couple days they found a bent driveshaft, which they replaced under warranty.
Why it wasn't immediately apparent when I picked up the car, I don't know.
Another thing that pops up is how many times someone breaks a driveshaft at the track and the output area of the trans gets damaged.

Re: pulsating driveline vibration? [Re: topside] #2652761
05/06/19 09:23 PM
05/06/19 09:23 PM
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mopower440 Offline OP
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Went out and tinkered with it a little after work. I still have it supported on jackstands under the rear frame. I removed the brake drums just to be extra sure it wasnt them. Still the same thing. Next, i put a floor jack under the rear chunk so i could raise and lower the whole axle to change angles..It didnt make it change any. Last, i put a 2x4 between the seat and gas pedal and got it to the rpm it does this the worst and looked up under the car with a light, both at the rear and at the trans..The driveshaft spins just as straight and smooth as can be!..So i sat in the car and played around with it..It starts at 1400 rpm and ends at 1900-2000. It is barely noticeable in 2nd gear at these rpms but very bad in 3rd gear at these same rpm's..After 2000 RPM it smooths right out..I really dont know what to think at this point. Transmissions arent cheap and i really hate to buy one without more evidence that the trans is the problem for sure..I just dont know.

Re: pulsating driveline vibration? [Re: mopower440] #2652773
05/06/19 09:56 PM
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Quote
[/quote] I would be suspicious of the transmission mount.[quote]


So my suspicion might be correct. Maybe try a polyurethane trans mount to get that last little bit of vibration out.

Last edited by captaindodge; 05/13/19 11:46 AM.
Re: pulsating driveline vibration? [Re: captaindodge] #2652777
05/06/19 10:08 PM
05/06/19 10:08 PM
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mopower440 Offline OP
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would it cause this violent pulsating vibration though?

Re: pulsating driveline vibration? [Re: mopower440] #2652793
05/06/19 10:46 PM
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Just to make sure that it only does this in gear, but not neutral confused Correct?
Do me a favor and check the harmonic balancer to see if TDC is still at TDC scope work

Last edited by Cab_Burge; 05/06/19 10:47 PM.

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Re: pulsating driveline vibration? [Re: Cab_Burge] #2652795
05/06/19 10:57 PM
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Re: pulsating driveline vibration? [Re: RapidRobert] #2652829
05/07/19 03:15 AM
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First thing I would do is make sure the angle of the trans output shaft and the angle of the pinion are the same when car is sitting on its suspension...you can download an angle app and use your phone. It is almost always that the joint angles are wrong.

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