The vibration that won't quit, what's next???????????

[747mopar]

Been following this thread hoping you would find it. I have been fighting the same problem for years and after breaking several 727 tailshaft housing parked it. What are you now using to check angles with and at what locations are you checking them at?

You need a surface perpendicular to the trans center line, I found the best way for me to check them was to pull the driveshaft and go off of the end of the tranny shaft and the pinion yoke (important to hold whatever your using straight up and down). I was going to buy a tool for checking the angle but found an app (clinometer) for my smart phone that works really well and yes I tested it against a level for accuracy (easier to read too). Make sure your checking it with the axle weighted, I've just been putting jack stands under the axle.

I've been told everything under the sun about the subject but it seams 85% agree that your tranny center line and your pinion center line need to be parallel to each other but sometimes it's necessary to point the pinion down a degree or 2 for axle wind up (mines a spot on match to the tranny). I'm just learning this stuff too but there's a video I posted in a thread "why driveshaft angles matter" that clearly shows what causes driveshaft vibrations if your interested. In a nut shell the U joint does not spin in a uniform manner at an angle but pulses and requires a matching or near matching angle on the other end to cancel each other out. They also want to see a degree at both ends to keep the needles moving for longer U joint life.

- - - Updated - - -

Drive it. More. When it is dry. I want more confirmation. This angle schmangle doesn't sit. As said, my trans, shaft, motor was shoved in and is smooth. No measuring anything. No shims. Sustain 74 or so and kiss triple digits if safe.

Well my guess is your angles are close enough, maybe they just got lucky? Another thing is my car being dropped 2" makes it a little less forgiving because of the driveshaft being so straight so that's another thing you got going for you?

It was wet and rainy when I tested the driveshaft but today it was dry and sunny when I tested the shims. I only drove it about 5 miles but this vibration wasn't a come and go thing, I knew exactly when and where it was going to do it every time so I'm confident and won't push my luck running the shaft so close to the floor. Once the mods are done I'll update this thread once I put some miles on it but it's a done deal in my book.

Why don't you jack your car up, set the axle on stands, level the car and check your angles? I'd be curious to see where they are.

 

[747mopar]

I'll have to take it back apart to do the mods so I'll take some pics of where I'm measuring and what the measurements are along with a link for the app I'm using. Hopefully I'll be digging into it tonight.

 

[440+6]

Normally the pinion angle on the stock suspension is down about 2° so that when you accelerate the pinion would come up about 3 to 4° keeping a happy medium to parallel.
Try some hard accelerations and see if you have a vibration, if you don't you're good to go otherwise you may need to lower it a degree or two.

 

[Budnicks]

The engine and transmission mounts can also transmit vibrations.

Yep What he said too

747mopar
I'm not sure if it's been covered or not, here it goes anyways,
but;
broken/badly worn engine or transmission mounts will cause vibrations sometimes too, ,
even a mount like them poly lock mounts will translate more vibrations,
I've ran solid engine mounts, with a poly trans mount,
that had some vibration issues under hard acceleration too,

Vibrations especially if the engine, crank or damper, converter/clutch, flywheel/flexplate
sometimes even pulleys & fans etc.
something wasn't balanced

brakes, drums, rotors, wheels, bearings, tires, axles, trans.,
anything that rotates, could be part of the issue,

it may be a combination of issues... god forbid

for your sake, sanity I hope not

sound like driveline stuff or pinion angle stuff to me thou,
at speeds or increasing speeds it gets worse...

I had a header that would hit the torsion bars under a load &
made a weird resonance/vibration drone, throughout the car,
it seemingly wasn't even really that close static,
I never figured that would be it either,
it took me forever to figure that one out...

carry one,
I'm just spit-balling, thinking out-loud & adding stuff

 

[747mopar]

Yep What he said too

I'm not sure if it's been covered or not, here it goes anyways,
but;
broken/badly worn engine or transmission mounts will cause vibrations sometimes too, ,
even a mount like them poly lock mounts will translate more vibrations,
I've ran solid engine mounts, with a poly trans mount,
that had some vibration issues under hard acceleration too,

Vibrations especially if the engine, crank or damper, converter/clutch, flywheel/flexplate
sometimes even pulleys & fans etc.
something wasn't balanced

brakes, drums, rotors, wheels, bearings, tires, axles, trans.,
anything that rotates, could be part of the issue,

it may be a combination of issues... god forbid

for your sake, sanity I hope not

sound like driveline stuff or pinion angle stuff to me thou,
at speeds or increasing speeds it gets worse...

I had a header that would hit the torsion bars under a load &
made a weird resonance/vibration drone, throughout the car,
it seemingly wasn't even really that close static,
I never figured that would be it either,
it took me forever to figure that one out...

carry one,
I'm just spit-balling, thinking out-loud & adding

Opinions and ideas are always welcome, if read above I finally got the damm vibration (pinion angled to match tranny). Since this vibration existed with the original 727 the only thing I can figure is the aftermarket leafs were holding the axle at the wrong angle or possibly the shackles weren't right?

- - - Updated - - -

With everything set where I want it it's time to make room in the tunnel since my car is lowered and the change in angle just ate up more real estate. Question........ I will be moving the bump plate for the pinion snubber (only 1/2" from it now) and was wondering what's the proper space between them?

 

[747mopar]

O.K. final update, finished all of the mods on the tunnel and got it reassembled for some cruising. Hard acceleration, 90+ mph, coasting, cruising, etc and nothing but pure pleasure!!!!! It was the pinion angle all along, I'm sitting at 3 degrees down on the tranny and 3 degrees up on the pinion and added a pinion snubber while I was at it............ Life is grand!

 

[conv67bdere]

O.K. final update, finished all of the mods on the tunnel and got it reassembled for some cruising. Hard acceleration, 90+ mph, coasting, cruising, etc and nothing but pure pleasure!!!!! It was the pinion angle all along, I'm sitting at 3 degrees down on the tranny and 3 degrees up on the pinion and added a pinion snubber while I was at it............ Life is grand!

WHooohooo . . . so we're road tripping to Carlisle ? ? I'm ready . . . can't wait to see how it rides 747Mopar ! !

Great news on finding the "cause" and getting it fixed ! ! !

 

[747mopar]

You have no idea how rewarding this is to finally have this solved. One problem......... because of some pinched nerves my clutch leg is giving me fits so you may have to do some driving?

 

[Xp29h]

Congrats!

 

[biomedtechguy]

O.K. final update, finished all of the mods on the tunnel and got it reassembled for some cruising. Hard acceleration, 90+ mph, coasting, cruising, etc and nothing but pure pleasure!!!!! It was the pinion angle all along, I'm sitting at 3 degrees down on the tranny and 3 degrees up on the pinion and added a pinion snubber while I was at it............ Life is grand!

Awesome! Thanks for the update

 

[Mopar Bill]

Check motor mounts, a weak mount could let exhaust make contact with something and cause a vibration that changes with engine speed.

 

[747mopar]

Check motor mounts, a weak mount could let exhaust make contact with something and cause a vibration that changes with engine speed.

Thanks, read post #66.

 

[Vince kf]

Man I'm at wits end with this vibration, I've checked everything that I can think of and replaced or addressed mostly everything. It's a very odd vibration, from 0 - 55 mph it's smooth as butter but once you exceed that and go into a coast like cresting a hill or just push in the clutch it vibrates pretty good (much like a really nasty exhaust drone). There is some vibration at higher speeds (65 mph +) and get's worse as you go faster but is most noticeable when unloaded (like cresting a hill). Today while driving it I'd take it up to 60 mph then push in the clutch and let it coast until the vibration stop and it always stops at about 53 mph? Hoping someone has experienced this same thing and can steer me in the right direction. This vibration existed with the original 727, driveshaft and rearend but after swapping the tranny to a T56 6 speed, installing a brand new driveshaft and putting a fresh set gears and bearing in it's mostly unchanged. The only thing that has minimized it is replacing the tail shaft bushing (had to shim it), it had .007" clearance and is now .003". Here's what I've done, checked for tranny clearance, checked for universal joint slop, checked and adjusted pinion angles, built a new gear set with all new bearings, checked and had leave springs reworked and replaced the slip yoke bushing.

i have a bad vibration too in my 73 Charger 400 4 speeds ! can't drive it on the highway , 40-45MPH + the car shakes very bad that almost all my bolts are lose!! i noticed that when i go uphill the vibrations decrease so am thinking the pinion angle , i also have a bad vibration when releasing the clutch don't know if that affect the highway vibration . ( motor mounts are good , transmission mount is new not sure about the quality ( made i korea ) , did the driveshaft twice , wheels are balanced ... so i will try to adjust the pinion angle

 

[Challenger340]

Just a thought here....
is this a Drum Brake Car ?

 

[747mopar]

i have a bad vibration too in my 73 Charger 400 4 speeds ! can't drive it on the highway , 40-45MPH + the car shakes very bad that almost all my bolts are lose!! i noticed that when i go uphill the vibrations decrease so am thinking the pinion angle , i also have a bad vibration when releasing the clutch don't know if that affect the highway vibration . ( motor mounts are good , transmission mount is new not sure about the quality ( made i korea ) , did the driveshaft twice , wheels are balanced ... so i will try to adjust the pinion angle

Explain "bad vibration when releasing the clutch".. are we talking about from a stop or while shifting gears? If you rev it in neutral does it vibrate?

 

[Babyblue66]

i have a bad vibration too in my 73 Charger 400 4 speeds ! can't drive it on the highway , 40-45MPH + the car shakes very bad that almost all my bolts are lose!! i noticed that when i go uphill the vibrations decrease so am thinking the pinion angle , i also have a bad vibration when releasing the clutch don't know if that affect the highway vibration . ( motor mounts are good , transmission mount is new not sure about the quality ( made i korea ) , did the driveshaft twice , wheels are balanced ... so i will try to adjust the pinion angle

Is the flywheel the correct external balance?

 

[Andy Davenport]

Man I'm at wits end with this vibration, I've checked everything that I can think of and replaced or addressed mostly everything. It's a very odd vibration, from 0 - 55 mph it's smooth as butter but once you exceed that and go into a coast like cresting a hill or just push in the clutch it vibrates pretty good (much like a really nasty exhaust drone). There is some vibration at higher speeds (65 mph +) and get's worse as you go faster but is most noticeable when unloaded (like cresting a hill). Today while driving it I'd take it up to 60 mph then push in the clutch and let it coast until the vibration stop and it always stops at about 53 mph? Hoping someone has experienced this same thing and can steer me in the right direction. This vibration existed with the original 727, driveshaft and rearend but after swapping the tranny to a T56 6 speed, installing a brand new driveshaft and putting a fresh set gears and bearing in it's mostly unchanged. The only thing that has minimized it is replacing the tail shaft bushing (had to shim it), it had .007" clearance and is now .003". Here's what I've done, checked for tranny clearance, checked for universal joint slop, checked and adjusted pinion angles, built a new gear set with all new bearings, checked and had leave springs reworked and replaced the slip yoke bushing.

 

[Andy Davenport]

Sounds like the crank shaft piolet bearing?? Or it might have been an automatic and the engine is not balanced with the flywheel?? Like the1975 440 auto can't be with flywheel because of external balance??

 

[Andy Davenport]

Drive shaft is consistent, check the killer bearing

 

[747mopar]

Drive shaft is consistent, check the killer bearing

I resolved my issue years ago, 2015 to be exact lol. Someone revived this old thread because they're having similar issues, read post #73.