I used to spend a lot of time, road testing to find vibrations. (ran a tire shop) Is there any speed, that it runs smooth? Does it vibrate more, when you accerate? IF it vibrates at all speeds, try running it up to a speed, and putting it in neutral, and let it coast down through the speed range..Have you changed wheels and tires?   If you cant get it out, this time of year, but have a place to run it, there are other things to check... I have friend with a 4 speed big block Monte that has a shake /shudder (and has it since 1986) He had changed "everything" on car except the trans, and it still shakes  He has taken my advice, and towed the car,down the road and it "doesnt shake" with and w/o motor running... He still wont pull trans ,so it still shakes...Carl

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 It has 411 gears in it right now but the last owner said that it always had that vibration, even with the stock gears.

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      I re-read this, and I thought of my Strato chief .. With the 8 inch rallies and P225/75r-15 tires it was smooth up to, and over 100..  I installed 7 inch rallies, and P235/70R-15 BFG's and it has a massive shake from 70 mph up  I am going to put other tires on, 2 at a time, to fix it.. So has your car  alwas had the same wheels  and tires on it?....You changed the trans, and two driveshafts...

I have changed all the rims and tires. It does it around 50 Mph in gear and out of gear. I changed the trans because it shook so bad that it broke a ear off of the transmission. Maybe I have two bad m-21 muncies? I never thought about the drive shaft angle, but it is at a stock ride height. It is the worst at 55mph then is less at higher speeds but still there and bad. The funny thing is my old 65 ss chevelle had the same problem but not as bad.

65sssd wrote:

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I have changed all the rims and tires. It does it around 50 Mph in gear and out of gear. I changed the trans because it shook so bad that it broke a ear off of the transmission. Maybe I have two bad m-21 muncies? I never thought about the drive shaft angle, but it is at a stock ride height. It is the worst at 55mph then is less at higher speeds but still there and bad. The funny thing is my old 65 ss chevelle had the same problem but not as bad.

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       If you ever had the chance to tow it, you could save another trans change.. towing it would check out the rear end.. spacing the trans mount would not be hard to do either.. 

I can't get it out right now to tow it, but that would eliminate the rear end. I should pull the drive shaft to isolate the rear end because it does it in neutral at 55Mph too.

Both of the driveshafts were balanced and the one was custom built one. I thought about rebalancing the drive shaft but both of the shafts acted the same. I don't know what the proper rear end gear lash is supposed to be and if that would do it. I am going to change the gears to a 373 or 355 by a prof rear end shop in the spring and if the vibration is still there hopefully that will fix it.

Neither of the drive shafts have universal problems. The drive shaft change didn't change the vibration when I swapped them out.

What about the pinion angle?  the upper control arms have cam washers.  Any manual will show how to properly adjust.

For the record.  Some of my chevelles/beaumonts have mild vibrations at certain speeds.  some worse than others.
A driveshaft balance problem is usually a cyclical vibration at higher speeds.
Maybe pull the drums and check axle ends for woble?

-- Edited by beaumontguru at 15:12, 2009-01-04

65sssd wrote:

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I didn't Know that upper control arms were adjustable. I thought they were fixed on stock 64-65 Beaumonts.Somebody must have that info at home? I don't have a 65 manual.

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I have been quoting from my 65 Malibu manual. Same drivetrain specs.  Attached is a scanned page with the specs and procedure.  Todd, can you bring it to size please if I am unsuccessful.




-- Edited by Johann65 at 16:14, 2009-01-04

Johann65 wrote:

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65sssd wrote:

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I didn't Know that upper control arms were adjustable. I thought they were fixed on stock 64-65 Beaumonts.Somebody must have that info at home? I don't have a 65 manual.

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I have been quoting from my 65 Malibu manual. Same drivetrain specs.  Attached is a scanned page with the specs and procedure.  Todd, can you bring it to size please if I am unsuccessful.




-- Edited by Johann65 at 16:14, 2009-01-04

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 This is as large as I can get it....In my Rag, I had trouble with my companion flange at the diff. Do you have another to bolt on?

65sssd wrote:

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I assume your talking about the two braces that go to the frame from the top of the diff? I have others but all the suspension bushings have been replaced. What did your rag do? Thanks for the enlarged photo.

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 No, the companion flange is the "yolk" that bolts to the pinion gear. Just the proper name for it, sorry! At the magical 50-60mph mark, my Rag would bounce and buzz the 4-gear shifter so bad it felt like it was going to come right through the floor! I tried 4 shafts that I knew some were good from other vehicles but finally I was told to try the yolk...With the exception of possible wheel balance issues, havn't done since '95 when I finally put it on the road, it is like day and night!!! Worth a try!!

 One thing I forgot to ask, there is no vibration with the car sitting still and reving the engine up to road speed, is there? Try it with and without your foot on the clutch! With the vibration being to be that far forward to break an ear, it had me rethinking! Are you sure the clutch and/or the flywheel are not at fault? It seems that you hane done everything else, and in my case it was the yolk and with very little left other than the diff itself, try that too.
 Yea, remove the nut and tap/pull the yolk off. You may require a new seal as well!!