The Stovebolt Site Forums The Shop Area Engine Shop 350 / 350 driveline vibrations

Hmmmm ,, ok ,, so this is about my wifes '73 Monte Carlo .
Nothing like a stovebolt , but I know some of you are very keen on the V8 , so I hope you can help.
I have balanced all the wheels and there is still a vibration , right on 60mph , it seems to come up thru the seat , not thru the steering wheel.
All I can see underneath is a litle slop at the front of the driveshaft . The yoke into the rear of the trans has a little up and down movement , it shows about an inch of bare shaft before it disappears into the trans rear seal.
Does this sound normal ?
Is there a bushing that normally wears there and is easily replaced ?
How firm on the splines should the yoke be , I am concerned at the movement there .
The U joints seem very sound .

Any thoughts gratefully recieved .

If I were you, I'd pull that driveshaft and take a serious look at the splines on the driveshaft as well as the splines inside the yoke. There shouldn't be any slop at all. And I'd make sure those U-joints are good.

I have balanced all the wheels and there is still a vibration

A vibration that comes up through the chassis, rather than through the column, ( you can feel it in the seat of your pants ) is usually from the rear of the vehicle. Although the wheels came into balance, you may have a radial runout concern in the wheels/tires. Or, a belt starting to separate.

JS

Thanks for your thoughts guys .
Piewagon , the car had been sitting for many years ( over 10 , it did barely 2000 miles in 18 yrs) and the tyres had flatspots on them , but after doing 600kms they seem better , I did lower the tyre pressure a bit , to try and get the tyres hot and smooth out the flat bits , looking at them now , as they are slowly rotated on the balance machine , they are pretty good.
Interesting thought on the plys seperating , the tyres were put on in '84 and hardly driven since .....
Baldeagle , The car has recorded 67000 miles , so I was concerned at the level of play at the yoke , I guess I will have to pull it and check further.

Dusty, the slip yoke design at the rear of the tranny has to have some movement...
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Look at the tranny rear mount to see if it is worn or loose.
Look at the driveline to see if the balance tab (if it has one or had one) has fallen off.
What does the gear oil look like in the differential?

I'll bet it's a rusting or siezing U-joint. A lot of the time a joint will go tight instead of getting sloppy from wear. Take the shaft off and work the joints in all directions to find the bad one. Replace them both while it's off. There is a bushing in the tailshaft housing. If it's bad enough to cause a vibration, you should have a substantial oil leak from the tailshaft seal. Then you need a new yoke, bushing, U-joints, a seal and an O-ring or gasket to make it right. Let us know what you find,
Scott

I'm blaming the tires, runout can be out but tire will balance. Beg borrow or steal two tires to try on the front, then you can tell for sure. Brian