Bad vibrations...

[493 Mike]

I should mention that when I measured the angle, I had the car in all four wheels on the ground.

When you checked the pinion angle did you follow the method outlined in the FSM? I'm just trying to be thorough.
Mike

 

[Dave145]

I don't have an FSM, but I followed an online guide.

As for the tires. First I jacked the car up and put a square against them and rotated them by hand. They all looked to be fine sidewall wise.

Then I started the car and let it run in neutral at 10mph. The right rear rim walks in and out a hair, but the tire appeared okay. The left rear rim tracked true, however the tread of the tire began shifting side to side even though the sidewall was still straight.

 

[oldbee]

Boy sure sounds like a broken ply in tire, it'll give you one hell of a shake.

 

[Centerline]

I should mention that when I measured the angle, I had the car in all four wheels on the ground.

When you measure the pinion angle you need to measure the trans output shaft as well. The important number is the difference between the two... not just the angle of the pinion.

 

[Dave145]

Tonight I will check the rest of the tires and rims to see how round they are. At least the tires aren't very old so the crappy one(s) should be covered by warranty.

The car sits level and drives down the road level. So while it's true the rear springs are toast, I don't believe it to be a pinion angle problem. But, everything here is suspect!

 

[Dave145]

Well, looks like I have one bad tire, and one bad rim.

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

 

[493 Mike]

Handle it Roy!

 

[Dave145]

Gave it another look over. Rotated all the tires around one at a time to the driver's side rear. End result appears to be 3 tires and 2 rims. The tread on the tires walks side to side and the rims kind of waddle as they rotate.

The test was performed at 20mph this time. Safe to say I believe we found a large amount of our problem.

I hope....

 

[oldbee]

I've driven cars with a broken tire belt that you could actually see the frt fender move sideways at 5-10mph. It happens, tires first.

 

[pushinblue]

1st rims 2nd bent or out of balance driveshaft

 

[khryslerkid]

I've driven cars with a broken tire belt that you could actually see the frt fender move sideways at 5-10mph. It happens, tires first.

I drove to work one day and everything was fine. Started home that afternoon and I thought my back wheel was falling off. Damn tire separated. Looked ok but spinning it you could see the tread waving like a snake.

 

[oldbee]

When you measure the pinion angle you need to measure the trans output shaft as well. The important number is the difference between the two... not just the angle of the pinion.

I agree, but I'd be more worried about the rear angle, unless the body/frame is really sagging.

 

[Centerline]

Well, looks like I have one bad tire, and one bad rim.

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

Question: I'm assuming the trans angle is -2.4 degrees (pointing down). Is the pinion angle also nose down? If so you have a pinion angle of 6.1 degrees which is fine for racing but too much for a street driven car. Excessive "U" joint angles can cause severe vibrations at different speeds. I'm not saying that's your problem, just something to keep in mind. If your pinion angle is up, then you are correct with a 1.3 degree angle which is OK.... however if you get any significant spring wrap under acceleration that angle could increase and once again cause vibration.

 

[Dave145]

Well back to square one. We installed a set of rims and tires that we're Roadforce balanced today and drove the car. No change in the vibration at all.

Crawled under the car, and to my surprise I saw the tranny pointing off towards the driver's side of the car. Further inspection reveals the motor is crooked too...as is the radiator. Everything is turned toward the driver's side of the car.

Should it be straight? I've done lots of reading, and everything says it should be crooked.

What's next? Tired of flinging parts at this thing.

 

[PP1RT]

How old are your shocks?? Any good? Cheapo's?

 

[Dave145]

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.

 

[miller]

Crawled under the car, and to my surprise I saw the tranny pointing off towards the driver's side of the car. Further inspection reveals the motor is crooked too...as is the radiator. Everything is turned toward the driver's side of the car.

If I'm reading you right, yes. Engine/trans is mounted at a slight angle to the passenger side. It's to add clearance for the steering box.

Rear u-joint body moved a bit between the caps on the driveshaft yoke.

Good deal you found, and fixed that! At least part of your vibration. I'd take a good look at the front u-joint, too!
Way it all sounds, you had a couple different issues, causing the vibrations. And, yeah, if your shocks are bad, I'd sure replace them.

 

[jim ritchie]

Enough said,,,,Time to get a good old mopar guy or a real mechanic(not parts changer) to go for a ride with you and see if you can pinpoint this vibration!Never throw money into parts until you are sure where the problem is!Almost all of us has had a problem with vibration somewhere on our cars,but can usually trace it down to it's source.Let us know how you make out.I am laying my money on drive shaft vibration,,if u-joints and shaft good,I have turned shaft 1/2 turn and vibration is gone. HOPE THIS HELPS.

 

[Glenwood]

Time to get a good old mopar guy or a real mechanic(not parts changer) to go for a ride with you and see if you can pinpoint this vibration!.

They're getting harder to find these days. Many are either retired or too old to bother or pushing up daisies. But I agree, if a guy can be found, it might save a bundle of time, money and aggravation.

When I completed my restorative work on the 64, I had swapped the rear with a non-tapered axle from a 1970 B. The pinion seemed to point down way too much. It looked like the trans pointed up about 4* and the pinion down about 12*! It had a terrible vibration when I pressed on the gas pedal or let off mostly on the highway, but would settle down when not accelerating. I added 5* shims and seemed to have cured the problem.

 

[miller]

Many are either retired or too old to bother or pushing up daisies.

Hey, are you picking on us old farts?

Thinking about what he found on the u-joint...could be 'someone' worked the shaft, not knowing what they were doing. It would be too easy, to drop the shaft, check both joints for play (could be worn out), and check if their the right ones, for both the yokes!