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Quick update:
Replaced tranny mount. Compairing old to new? Big difference! The old one looked like it was leaned over to one side.
Going to remove tail shaft housing tonight to replace bushing. I got a kit off eBay that has all the seals and gaskets.
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Another update:
Tail shaft removed. Tail shaft bushing smeared down to the tin. Replaced bushing. Replaced speedo gear seals. Reinstalled tail shaft, what fun that was! I got that SOB back on there! Had to ruin a pair of needle nose pliers for that snap ring.
Installed my new transmission mount. The transmission had to be pushed over 3/16 to get bolts to start. As if the motor was mounted crooked in the car.
Anyway. Need to re fill fluids. Install exhaust, then test drive.
i also re measured my angles. Engine / Trans 1.8 deg down with repeat measurements!
At the rear pinion. Things get stupid. Measure @ the cup. 1.8 deg uphill. Rotate 180 deg. Measure again @ the cup. 2.6 deg uphill.
I think I have a bent yoke? Or pinion shaft.
Stay tuned:
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Feeling DEFEATED!
New Transmission mount and new Tailshaft Bushing.
At 30 mph on jackstands the car shakes so bad!!! Way worse! Way BAD! Smooths out past 30 but its still cycical vibration. In and out.
Bent driveshaft? Bent yoke? I watched it idling in gear and the driveshaft seems to have alot of runout at the middle of the shaft. at the yokes it looks dead steady.
Im kinda at wits end here.
So?
To recap. Everything Ive done to tighten up, refresh and restore in the driveline makes everything worse!
New leaf Springs, Shocks, U-joints, Transsmission mount, Tailshaft bushing, Correcting the drive angles.
BEER TIME
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I wouldn't think you should have any visible run-out in the shaft
The Idaho Andy
I love the smell of race fuel in the morning
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I am not so sure that the driveshaft doesn't have some natural runout. Not sure what is good or bad. How about mounting an indicator under it and measure the runout by turning the shaft by hand? Then call a driveshaft company and ask their opinion on what the runout can be.
Can you post some pictures on how you are doing your angle measurements?
When you rotate the driveshaft by hand and try to move it up or down, is it tight or is there excessive looseness?
Is there a driveshaft repair facility near you where you can take the shaft to get inspected (including the ujoints)?
Are you running the car with the wheels on or off?
I also don't know how much different the system behaves on jack stands versus driving on the road. But if it is shaking on the jackstands something is definitely wrong.
I would try it with the wheels off - if you haven't done that already. If it still is real bad I would focus on the driveshaft (including ujoints) and u joint angle.
I am on vacation next week. I can duplicate your tests on my car and see if we get comparable results or see if there is something blatantly different. I do have an aftermarket shaft in it right now.
Did you check the driveshaft length - you do have new leaf springs which can change the driveshaft length requirements if they are different than the stock ones. The yoke should slide about 1 inch out of the tranny when the rear u joint is fully seated in the pinion yoke.
67 Coronet 500 - 9.610 @ 139.20 mph
Owned Since 1981
Daughter's Car
67 Coronet 500 Street Car with AC
13.300 @ 101.75 mph
69 GTX clone - build in progress........
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When doing your test, are the jackstands under the axles or on the frame rails?
I love Mopars so much I'm date coding the skid marks in my underwear.
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As Mark mentioned before, you could have a brake issue. Try removing the drums (don't touch the brake pedal else you'll be picking up brake parts all over the floor), put the tires back on and see what happens. Just remember to not touch the brakes to stop the wheels, shut the car off and let them come to a stop on their own.
What you really need to do is figure out a way to eliminate different parts for sure.
President, New England chapter of Coronetaholics anonomous.
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Okay:
last night after dinner I went out and ran the car in Park. I don't know if you all remember a while back when I was fighting a engine shutter I called it at about 950 rpm? Distributor tuning made that go away sorta speak. Well at 1100 rpm on the dot! The engine shakes so hard as if the steering wheel was gonna smack the windshield.
I shut the bastard off and went to bed!
To Markz questions:
New leaf springs. On jack stands on axel tubes. Yes wheels are on. 3 inches of drive shaft yoke shows when installed. As if the shaft was too short. I will remove wheels tonight.
The way I am measuring my angles is: I use a socket about the diameter of the u joint cup. I take my cube digital angle finder and stick it to the bottom of the socket, then insert socket to flush up to the pinion yoke u joint cup at dead 6 o'clock posisition. I do the same at the transmission yoke. Note. If you measure at the driveshaft cups, you will get the angle of the driveshaft.
I will take pictures tonight.
I might put the old transmission mount back in and see if it goes back to as it was? If it still shakes hard it has to be the new bushing taking up clearances meaning the driveshaft has a issue and is not running true.
Also this driveshaft has the big ring on it. No weights at that end. At the pinion end there is a weight. My shaft is 52 inches on center. Using precision g316 joints.
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I also want to confess to a sin. That new transmission mount was a $9.00 eBay special.
lets hope that the old one makes me happy!
Posts: 447
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Replaced the new cheap tranny mount with old one.
Ran the car on jackstands with wheels on, no hint of the modulating vibration up to 50 mph. On jackstands and spinning unsprung rubber scares me. Hate to ruin a $125.00 tire!
That vibration is absent!
My thoughts! My driveshaft is not original, someone replaced it with whatever worked. It is too short! It caused the splines on the tube to wear. Then the tube could wobble on the output shaft.
Next it took out the tailshaft bushing!
Now the driveshaft at the transmission output is free to find its own rotational centerline based on rpm, load, natural frequencies, etc
I replaced the tailshaft bushing and now its a million percent better. Basiclly making the driveshaft run true agin. I know this bushing will fail again if left in this condition.
Would you agree?
Im going to buy a new yoke, and either a junkyard driveshaft the proper lenght or have a shaft made.
I tried to upload photos.. I lock up and loose everything written.
