[jeffa55]

My car is a 72 Ventura with a 400 ci chevy, 200 4r trans and a 4.10 posi and I have two problems I cannot figure out.

#1 - The car vibrates on the highway. I believe it is coming from the front end since the steering wheel moves pretty bad. The vibration seems to occur from 50-85 and may even continue on up so it doesn't seem like a tire problem since it doesn't really smooth out. Since I bought the car I have changed the front wheels/tires, balanced the driveshaft, changed the front springs and the vibration stays the same. Could it be the alignment? The wheel bearins seem good. The car does have front drum brakes - could the drums be unbalanced? Any ideas??

#2 - There is a 'clunk' from the rear end when backing up, turning and goving over a small bump. It happens every time I leave my driveway (I back out). Even if I am going very slowly there is a loud clunk from the drivers side rear tire. I have made sure everything is tight and it is. The rearend is new and so I think it has something to do with that. It 'almost' seems like the diff isn't slipping correctly - but I would think that I would notice that in regular driving too.

Any help/ideas would be greatly appreciated.

 

[71SS454]

That clunk could be from alot of things. Bad spring bushings, broken spring, bad axle, bad crosspin, a broken part in the carrier like the spider gears, or you just may be hearing a bad u-joint. A bad u joint will also create a vibration at speed. Now if you're driving down the road and the vibration starts, what happens when you put it in neutral? If it is in the front end it could be a drum out of balance, or bad bushings, bad ball joint, worn idler arm, bad pitman arm, worn center link, even a bad rag joint.Are your rims running true, nothing bent? Try putting a rear on the rears on the front and see if it changes. There's alot to check yet.

 

[jeffa55]

Thanks for all of the info - lots to take in

1 - The clunk started when this rear end went in. The rear end is noise (howls that you can hear over about 30mph and quiets down when you are off of the gas). The guy did put new axles in it, but I am pretty sure the problem is something in the axle. I want to make sure that the axle isn't going to fall out or anything really dangerous. Is there an easy way to check that? Also, the rear leafs are 'new' (out of a junk yard) but they look great. I have noticed that those 'bands' around the springs have moved since I put them on. Is that normal?

2 - I am about 100% sure the vibration is not the wheels /tires. The car was vibrating so I:
#1 - rebalanced the wheels/tires - no difference
#2 - switched the left to right and right to left - no difference
#3 - bought a brand new set of wheels with new tires - no difference.
I did have a mechanic jack up the front and mess with the tires to check the bearings and/or ball joints and he said everything felt fine. The steering box/arm have been replaced, but same rag joint. What should I check next? Can I swap the rear drums and front drums?

 

[justin72nova]

get an alignment for the car to fix the vibration.

 

[71SS454]

If the rear end howls, the ring and pinion aren't set up right, or you could have a bad bearing in the rear end letting your pinion move around. That can cause a vibration as well. Try unbolting your driveshaft and turning it 180 degrees and bolting it back up to make sure it's "phased" correctly. This is a long shot, but it has happened before.

 

[jeffa55]

Unfortunatley, I am 100% sure that the vibration is not coming from the shaft or the rear end since the rear end has been completely swaped out and the driveshaft has been removed twice, balanced, new u joints, etc and the vibration has remained 100% the same.

 

[hawk7745]

Do you have leaf springs or coils?

 

[jeffa55]

Leaf springs in the rear, coils (Hotchkis) in the front.
My biggest fear is that the clunk means that something could come apart in the rear end. Is there any quick way to check the axles to make sure they won't fall out?

I had heard that the alignment couldn't cause a vibration... true or untrue?

 

[Burke]

I know you're sure it's not the rear ens or driveshaft, but have you checked the pinion angle relative to the output of the transmission? These two angles should be aprox. equal and oposite under load, (pinion angle down 2 to 8 degrees at rest depending on HP and rear suspension type). If these angles are to far off you can get a really bad vibration at speed.

Good luck.

 

[jeffa55]

I have never checked that, but I would assume it was not the problem (just because the old trans with the original rear end had the same vibration. When you say that the pinion angle should be 2-8 degrees down, do you meant that the rear end should basically be 'tilted' downward about 2-8 degrees from trans output (so if I drew a line from the trans to the rear, the pinion should be angled down 2 to 8 degrees from that line? If it is tiled down more than that, how do I correct that problem?

Thanks for your help!!

 

[71SS454]

How's your body mount bushings look?

 

[Burke]

Use an angle finder to measure the angle (relative to gravity) of the output shaft of the trans. Then measure the the angle of the pinion yoke. They should be oposite. If the trans points up the pinion must point down. If the trans points down the pinion must point up.
Because of torque aplied to through the wheels when you accelerate the pinion tries to rotate up and the rear suspension fights it, but it does move some so you need to build in a little extra down angle into the pinion to compensate so under load the angles are equal and oposite.
I hope that helps.

 

[jeffa55]

Thanks for the info - I will check the angles

I have never looked at the body busihings... I will look at that. I assume cracked is bad

 

[6T6NOVA]

I bought a parts car years ago. The rear was a 10 bolt 5 lug. Which is what I needed for my 62 Chevy II. After driving the car for about a day the rear end started making a noise like you are talking about. Real bad in reverse. The shaft that goes thru the ring gear carrier that holds the spider gears was all worn. The carrier was even damaged. I had to buy a new ring gear carrier and spider gear shaft.

Hope you find your problem.

Bryan

 

[jeffa55]

Well, I don't believe it is the trans/rear end angle. They are almost both dead on at 3 deg in opposite angles (trans up, rear down). The body bushings looked perfect.

A couple of questions:
1 - can the alignment cause vibration? I have NO reason to think it is out of algnment as the car is not pulling, but coudl it be out? And could that cause the vibration??

2 - Can the drums be out of balance causing the vibration? It just seems like the next logical vibration point - since they are spinning too!!

3 - How about wheel bearings - can they cause a vibration? Or do they usually show other signs when failing?

The vibration is very frustrating and I really want to get it fixed.