Bad vibrations...

[PP1RT]

Shocks are old and crappy, but I can't believe that's what's causing this car to feel like it's coming apart underneath at speed.

Crawled underneath it tonight. Trans mount is solid. Loosened bolts to let trans rest and make sure it wasn't shifted, then snugged back up.

B&T joint appears to be okay (minus shot dust boot)

Rear u-joint body moved a bit between the caps on the driveshaft yoke. Installed a fatter clip in one of the caps (clips that came with u-joint were smaller than the grooves in the caps) and reinstalled. Fits tightly now the way it should.

Put some shocks on it now before you do anything else! Any small vibration will be amplified by bad shocks. The wheel hop becomes worse until you stab the brakes i bet. Those tires act like basketballs. I'd bet money on bad shocks!

 

[oldbee]

JUST bad shocks? I just can't go along with that,although a possibility. Has to be something else& maybe shocks are amplifying it?

 

[PP1RT]

Had a 2wd pickup once do the same. That is all it was. 1 shock doing nothing and another with very little resistance..

 

[oldbee]

PP was it a Ferd by chance? Heard of that problem more than once, especially with that twin-I beam suspension on the front.

 

[PP1RT]

PP was it a Ferd by chance? Heard of that problem more than once, especially with that twin-I beam suspension on the front.

72 GMC

 

[jim ritchie]

Dave,I agree with Miller,,if 70 is a old fart I is one,,,but have had many of these old 60's Mopars from band new to today and your problem is not that big of deal,,,you have chased it around the block and back,with out really moving ahead,,,please check that drive line,,90 percent of the time,,that's where it is,when it vibrates the whole car,,,and you have ruled out almost everything else,could be binding,U-joints, not matched,worn,tight,not in line,Drive shaft not balanced,bent,out of line, yokes worn ,,,even bearings in tailshaft,,or diff,etc ,etc.Good Luck ,Dave,,,,,you'll get it and be a happy guy.

 

[Dave145]

The u joint is brand new. As I had said before, I was able to tighten up it's tolerance in the cross by using a thicker clip in one of the caps on the driveshaft yoke. That's where it needs to be now thankfully. After doing this, the vibration is a *bit* better.

The ball and trunnion joint really didn't appear to have any wear in it when I took it apart a few months back. The cup slides felt fine, the balls showed no obvious wear and the needles we're all straight and in place. I cleaned and re-greased everything, checked that I had all the parts installed correctly, and reinstalled it in the car. Still, no change in vibration.

Short of banking on a bent driveshaft, I'm not sure what else to see down there.

The trans mount is 100% solid, as are the engine mounts. Checked to make sure they are all tight and the rubber is good last night.

The shocks are worn out and pending replacement. But I can't see that being the sole cause of the issue.

Different rims/tires changed effectively nothing.

Front end being completely rebuilt changed nothing either.

Verified the brakes aren't hanging up at all as well.

All front wheel bearings have been replaced and torqued to spec. Rear outer bearings too.

Currently, the symptoms are this:

- Vibrates from 10-25 and 40-45 when accelerating only. Coasting or cruising and it goes away.

- 50-69 it's fine! Not even a shimmy!

-70 the tremor starts. Feel in rear of car.

-75 shakes windows, steering wheel, and floor

-80 is too scary to continue. Let off gas and coast down. Shakes entire car top to bottom. Changes rearview mirror position.

-If I'm super lucky, sometimes the car will be able to drive up to 70 without vibrating. Then it comes in strong at 75 and keeps going.

- Vibration lessens (does NOT disappear) when put into neutral while cruising at offending speeds

- Terrible vibration with brakes, but the drums are warped (great...more money)

 

[miller]

The u joint is brand new. As I had said before, I was able to tighten up it's tolerance in the cross by using a thicker clip in one of the caps on the driveshaft yoke. That's where it needs to be now thankfully. After doing this, the vibration is a *bit* better.

New doesn't matter. My question is, if the u-joint is the right one?
If it is, okay. Just trying to make things clear, since, from the sounds of it, there was some issue with it's fit.
On Mopars, there are a handful of different 'sized' u-joints, and depends on which yoke you have, both on the shaft, and the rear end. There's even combination u-joints made.

Any issue with a driveshaft, will easily shake badly.

 

[Dave145]

Yes it was the correct joint. Measured it against the old one when I purchased it.

 

[Centerline]

I still believe you somehow have excessive angles in the driveline. Vibration on acceleration and not on coast or deceleration are classic symptoms of this.

 

[jim ritchie]

It tells a lot ,,when you put in a different size clip,,,,take drive shaft off,,,turn drive shaft by hand ,when out,,,do both U-Joints flop freely on their own when turned,,,,if not ,,that means the joints are too tight,,,and will vibrate the whole shaft when installed,,,maybe you know this,,,but this is a must!Also the drive shaft needs to be tuned or balanced,,this is also a must,,,when things have been changed,,,sometimes you can just try to bolt it up one way,try it,,,if still vibration,,unbolt and turn 1/2 turn and rebolt and take it for another drive,,,if all of the above still doesn't work,,pull your hair out a wipe your *** with it,CHEERS

 

[jim ritchie]

Can't get your problem out of my head,,,short of coming to your place and fixing it,will try on line.You said that you put a different size clip in ONE cap to tighten it,,,I have never done that,,,and is a no,no,,,if it was me, that drive shaft would be off in a heart beat and replace both u- joints,for sure,,,new or not,CHEAP FIX,,,you don't have to believe me,you can just vibrate down the road.CHEERS

 

[jim ritchie]

Thought,you didn't see Thunderlugs,,,but you did,,,and I think he would have given you his thoughts about the vibration,,,,Hope you get your answer,,,with the help of fellow members,,that have had the same issues,CHEERS

 

[khryslerkid]

Useing a different size clip on one cap? Thicker will offset the u joint. Wrong joint or yoke is opened up for some reason.

Fix this and double check pinion and trans angles with car sitting on the ground.

 

[Dave145]

I cannot imagine how pinion angle could be to blame. This is a bone stock car that sat all it's life. I double checked all the angles and they are the same as I said before. Only way I can imagine it would be off is because of the crap *** engineering that offset the motor in the car.

U Joint clip I installed was maybe a hair thicker. Looked identical side to side, but fit better in the u joint groove.

To be clear, the driveshaft has 1 u joint. The other is that crappy ball and trunnion joint. Both joints flop and roll fine with the shaft off the car.

I don't know of any shops around here that could balance a shaft with the BT joint on it. Most only deal with new stuff.

 

[oldbee]

Didn't you say the rear springs needed replaced?Maybe sagging too much; as an aside, my dad had '63 Fury Zeibarted one time and a couple spots on d/shaft had that undercoating on it and caused a vibration. Scrapped off that undercoat and it was back to normal!

 

[khryslerkid]

Didn't you say the rear springs needed replaced?Maybe sagging too much; as an aside, my dad had '63 Fury Zeibarted one time and a couple spots on d/shaft had that undercoating on it and caused a vibration. Scrapped off that undercoat and it was back to normal!

Funny you should mention that. I'm cleaning up my driveshaft and the coating is approximately 50mm thick!

And those "crappy" ball and trunnion joints were used behind hemi four speeds back in the day!

 

[Thunderlugs]

Funny you should mention that. I'm cleaning up my driveshaft and the coating is approximately 50mm thick!
View attachment 510950

And those "crappy" ball and trunnion joints were used behind hemi four speeds back in the day!

I don't think anyone gets parts cleaning results like you do! Looks like Chrome!

 

[Centerline]

Pinion angle is 1.3 degrees.

At the tranny it's 2.4 degrees,
At the pinion its 3.7 degrees.

Anything else to check? Sure looks like tire/rims to me

You didn't mention if the trans was pointing up or down and the pinion up or down. Both pointing down = bad. Both up = bad. Trans down and pinion up = good.

 

[Dave145]

Interesting about the ziebarted driveshaft...kinda makes me laugh a bit.

The trans is flat or slightly pointed down, and the pinion is also flat or slightly pointed up.

The rear springs are weak, but the car sits level driving down the road so I'm told (I've had someone follow me around and watch the car drive).

It's not so much I think the B&T joint is terribly crappy, but the 2 pole design of it is a bit lackluster. No matter what you do with it, it is never going to be perfectly balanced or centered. If it had 4 poles or even 3 like later Mitsubishi's, it may be better. Plus, getting parts isn't the easiest thing I've ever done either! Only kits on fleabay are for much much older vehicles, with the "newest" kit being for a DeSoto.

Sometime next week I'll pull the shaft out again and look everything back over. I have a friend that's got a few of these cars for parts, so I may pick up a gently used driveshaft from him and drop it in to see if that helps at all.

Just sucks because my pockets are about as deep as a puddle......