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

[747mopar]

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.

 

[eldubb440]

i know you would feel a front tire in the steering wheel, but could it be something as simple as an out of balance rear tire/wheel?

 

[747mopar]

My next move is to have the shop that made the driveshaft take another look at it. Next, (if I can find one) borrow a whole rear end for a couple hours just to eliminate that possibility and then pull the tranny for a full inspection? I'm lost, is there such a thing as a shop that specializes in this kind of thing?

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i know you would feel a front tire in the steering wheel, but could it be something as simple as an out of balance rear tire/wheel?

I wouldn't think so seeing how it does it the worst when you push in the clutch, a wheel out of balance usually gets worse with rpms and wouldn't get worse coasting?

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I am getting it re aligned this week so I could have him check the tires anyhow.

 

[Hemi Rebel]

Typically at that speed you would look for a wheel/tire issue. I cant feel it so thats what i suggest you check next. Take them for a road force balance.
If that fails, then i suggest you get a sirometer. With that you can determine the frequency of the vibration. Knowing that and at what speed the car is at we can hopefully determine the source of the vibration

http://www.treysit.com/16.html

 

[Dennis H]

If it existed with the 727, then how is the clutch a factor? Gonna ask a shitload of obvious questions now. Did you try shutting off the engine and do the right/left test? If the vibration was there before the swap, I'd think pulling the trans would be a last attempt. I got a shock with a 74 then 104 mph vibration. Shop says 2 wheels are bent. He fooled with the roadforce etc and got it barely noticable. One bent wheel is a fairly new wheel bought through Summit so I am shopping for wheels.

 

[747mopar]

Can you buy those sirometers around here or do you have to order them? What do you fasten it to? What's road force balance?

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If it existed with the 727, then how is the clutch a factor? Gonna ask a shitload of obvious questions now. Did you try shutting off the engine and do the right/left test? If the vibration was there before the swap, I'd think pulling the trans would be a last attempt. I got a shock with a 74 then 104 mph vibration. Shop says 2 wheels are bent. He fooled with the roadforce etc and got it barely noticable. One bent wheel is a fairly new wheel bought through Summit so I am shopping for wheels.

The clutch isn't a factor I'm simply saying that it's worse when there is no load on the driveline, an easy way to simulate no load is to push the clutch in. Before with the 727 it had 3:55s so it did it at a much higher rpm than now with the 4:30s and also did it worse in a coast situation. Roadforce???? Please explain a little better, I'll check all of the wheels for runout and get all of them checked again for balance.

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Shut off motor and do right left test???????????

 

[Dennis H]

Yes. Make it quiet, steer gently left then right to see if there is an increase or decrease. Turn off the fuel pump if it is electric. Roadforce is that fancy expensive way to. check balance with weight applied. Get creative. Make a pal ride in the trunk. Whatever it takes. Touch the brakes. See if load makes a change.

 

[747mopar]

I'm lost with the whole checking balance with weight applied? What am I checking? Not being a smart *** I'm just not fully getting it.

 

[Hemi Rebel]

The sirometer works by just holding it against the dash, or whever you feel the vibrations. Will need a helper for this obviously, and,
https://youtu.be/DQxVAssnbp8

 

[Dennis H]

Roadforce is a fancy balancing machine that some shops have. Chasing vibration is a tough gig. All the baloney of the degree angles and such with my shoved in TKO never panned out. Turned out to be wheel or tire balance.

 

[747mopar]

The sirometer works by just holding it against the dash, or whever you feel the vibrations. Will need a helper for this obviously, and,
https://youtu.be/DQxVAssnbp8

Gotcha, now I see what your talking about. Thanks

 

[dvw]

I've been chasing a similar vibration in my 73 Challenger. Very close to the same speed range. Clutch in still shakes. It is definitely drive shaft speed (easy to tell by the speed of the vibration, tires are more slower frequency). Housing, rear axle chuck assy, axle shafts, drive shaft have all been swapped. Pinion angle is dead nuts 1.5 front and rear. The bell housing run out is less than .005" and the face has been corrected to 90 degrees to the crank C/L. The only part I haven't swapped is the 833 trans.Up to just over 50 it's perfect. It had a 2.76 gear in it when first built. Never shook. I did a burnout and shattered the trans yoke and cracked the tail housing. New yoke, housing and bushing. It's shook ever since. I'm thinking I may have bent the trans output shaft. However it makes no noise and is the best shifting 833 I've ever had.
Doug

 

[benno440]

do you have a gopro, maybe mount it under car then go for a drive then keep putting it in all different locations to see if there is a wobble or vibration in anything as you are cruising around.
just a thought

 

[747mopar]

do you have a gopro, maybe mount it under car then go for a drive then keep putting it in all different locations to see if there is a wobble or vibration in anything as you are cruising around.
just a thought

Been thinking about that actually, I'll have to make a bracket though.

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I've been chasing a similar vibration in my 73 Challenger. Very close to the same speed range. Clutch in still shakes. It is definitely drive shaft speed (easy to tell by the speed of the vibration, tires are more slower frequency). Housing, rear axle chuck assy, axle shafts, drive shaft have all been swapped. Pinion angle is dead nuts 1.5 front and rear. The bell housing run out is less than .005" and the face has been corrected to 90 degrees to the crank C/L. The only part I haven't swapped is the 833 trans.Up to just over 50 it's perfect. It had a 2.76 gear in it when first built. Never shook. I did a burnout and shattered the trans yoke and cracked the tail housing. New yoke, housing and bushing. It's shook ever since. I'm thinking I may have bent the trans output shaft. However it makes no noise and is the best shifting 833 I've ever had.
Doug

This all sounds very simular, I'm fairly confident mine is driveshaft related as well because it used to do it at a much higher speed but with the gear change it's now all the way down at 60 mph now. Same thing regardless of what gear your in, it's related to the driveshaft rpm it would seam. I'm still going to check everything else, let me know if you find it.

 

[uk-maxie]

My brother and I have a 63 Polara that had had some vibration ever since we got it 11 years ago. Although we've replaced some items in an attempt to eliminate it (prop shat & drive shafts) it's still there and has possibly even got worse in recent times.

So after much procrastination read2 we arranged to take the car to one of the drag racing / US car specialists over here, who we know has dealt with these issues before.

We dropped the car off last Friday morning and by mid-afternoon he was on the phone to me saying that he'd found that the rear axle yoke, where the UJ sits, was worn to the extent that the UJ could move around by 1mm when clamped in position.

The plan is to fit a used yoke that he has in stock (used but without the wear!) and a new sleeve, which is due in today (Monday).

Fingers crossed, this is the cause of the vibration.

We thought it was going to be the pinion angle but he says it's ok at 1.5deg (as mentioned previously in this thread).

I'll let you know how we get on but in the meantime, might be worth checking your yoke for wear if you haven't already :eusa_think:

 

[uwss]

FYI, my son had a bubble on his front tire we found that caused one hell of a vibration at high speed. Pull those tires off and look at them. Have the wheels and tires rebalanced. I doubt the driveshaft would be the issue.

 

[747mopar]

My brother and I have a 63 Polara that had had some vibration ever since we got it 11 years ago. Although we've replaced some items in an attempt to eliminate it (prop shat & drive shafts) it's still there and has possibly even got worse in recent times.

So after much procrastination read2 we arranged to take the car to one of the drag racing / US car specialists over here, who we know has dealt with these issues before.

We dropped the car off last Friday morning and by mid-afternoon he was on the phone to me saying that he'd found that the rear axle yoke, where the UJ sits, was worn to the extent that the UJ could move around by 1mm when clamped in position.

The plan is to fit a used yoke that he has in stock (used but without the wear!) and a new sleeve, which is due in today (Monday).

Fingers crossed, this is the cause of the vibration.

We thought it was going to be the pinion angle but he says it's ok at 1.5deg (as mentioned previously in this thread).

I'll let you know how we get on but in the meantime, might be worth checking your yoke for wear if you haven't already :eusa_think:

When I did the tranny swap I upgraded the universals and the yoke so that's all new and tight. Thanks

 

[72Fourspeed]

At 55ish, I'd suspect tires too.Swap out the set of four with known good ones & see what happens. Maybe find a Hunter on car balancer for your rims/tires ? Good luck, keep us posted.

 

[747mopar]

Dropping the car off Thursday morning for re alignment and will have all the wheels and tires checked although he doesn't have the fancy weighted machine.

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Still suspicious of the driveshaft angles, I know Dennis H "look elsewhere haha" but I'm one of the idiots that lowers my car so it also serves as a road grader. Because of it being lowered another inch the pinion and driveshaft angles are nearly zero now (pretty much straight) which isn't good. It would explain the worsening condition while at coast too, as soon as you go into coast the load is removed causing the pinion to drop making the angle even worse?????? Just thinking

 

[bm02tj]

When looking at driveshaft angles look at offset angles as well and with your car lowered it can increase problems
you may need to add a torque bar to stop spring wrap both ways