Bad vibrations (Part 2!)

[Dave145]

Hey everyone,

Some of you may remember my post last year about my '64 Polara having an undefined vibration that nothing seemed to cure. Well I'm back to update and say it's still here. In short, here's a list of things that have been done/replaced to attempt to rectify this issue:

-New upper/lower ball joints
-New inner/outer tie rods
-New pitman and idler arms
-All new front end bushings
-Front end alignment by a reputable shop
-New gas front shocks
-New air shocks in the rear
-New driveshaft with trunnion delete
-New U-joint at the rear axle
-New 5-leaf rear springs and bushings
-Two different sets of rims/tires. Both sets checked for runout and balanced. Both sets of wheels/tires professionally balanced as well.
-New front and rear brake drums (rears converted to slip on drums)
-New exhaust and hangers
-New electronic ignition system and coil
-Full tune up and carb rebuild

This thing still shakes at 70+ mph. It's felt in the floor and seat mostly and seems to eminate from the rear (or so it feels going down the road).

I'm at a complete loss guys. It runs and drives great for what it is. It goes down the road pin straight, has all the power a 318 poly can have in stock form, and rides REALLY nicely when kept below 65. At 65 you can feel a bit of shudder, and by 70 it feels like it's wheels are basketballs.

So where to next? I'm still not made of gold to keep throwing money at this thing, but I'm determined to fix this good awful problem.

 

[motorhead55]

Check you driveshaft angle.

 

[super-bee_ski]

Please add to the List : Tires professionally balanced.
(I know you must have checked this also)
That way, one less thing to include in the equation.

 

[Dave145]

I forgot to add that to the list. I had the tires balanced as well.

 

[the mississippi madman]

Warped flywheel, or unbalanced torque converter?

 

[747mopar]

Check you driveshaft angle.

BINGO! Being high speed sensitive points to a driveline angle problem. Does it worsen or lesson under load or in coast, if so it's most likely your pinion angle. Typically if the angle is to low it won't vibrate under heavy load but will once you reach cruising speed. You can buy several different degrees of shims that you place between the axle and springs that allow you to dial it in. For a starting point the pinion angle should match the drivetrain angle then fine tune from there.

 

[70sixpkrt]

If it's a 4 speed, did you have the pressure plate balanced to the flywheel?

 

[HEMI-ITIS]

Warped flywheel, or unbalanced torque converter?

Does the older 318 have a balance weight on the converter that may have fallen off??????

 

[Dave145]

I'm not sure about weights on the converter or balancer. It's got a 727 behind it and as far as I can tell neither of them have ever been apart. It vibrates regardless of being under load or cruising. I recall checking the angle last fall before I put the car away and it was fine then even with worn out rear springs.

 

[the mississippi madman]

What rpm range does it vibrate in or is it all the time

 

[Dave145]

It's around 2300rpm. I forget the exact number but it starts exactly at 70mph every time I get the car going that fast .

 

[NOSTRT980]

trans mount???

 

[67belvedere/225]

I have the same issue , I played with the drive shaft anlge and inpoved a lot still there a bit , will take a day to sort it out
I shimmed the diff and it got better. there was a post here about it a few weeks ago I will see if I can find some info

Hey everyone,

Some of you may remember my post last year about my '64 Polara having an undefined vibration that nothing seemed to cure. Well I'm back to update and say it's still here. In short, here's a list of things that have been done/replaced to attempt to rectify this issue:

-New upper/lower ball joints
-New inner/outer tie rods
-New pitman and idler arms
-All new front end bushings
-Front end alignment by a reputable shop
-New gas front shocks
-New air shocks in the rear
-New driveshaft with trunnion delete
-New U-joint at the rear axle
-New 5-leaf rear springs and bushings
-Two different sets of rims/tires. Both sets checked for runout and balanced. Both sets of wheels/tires professionally balanced as well.
-New front and rear brake drums (rears converted to slip on drums)
-New exhaust and hangers
-New electronic ignition system and coil
-Full tune up and carb rebuild

This thing still shakes at 70+ mph. It's felt in the floor and seat mostly and seems to eminate from the rear (or so it feels going down the road).

I'm at a complete loss guys. It runs and drives great for what it is. It goes down the road pin straight, has all the power a 318 poly can have in stock form, and rides REALLY nicely when kept below 65. At 65 you can feel a bit of shudder, and by 70 it feels like it's wheels are basketballs.

So where to next? I'm still not made of gold to keep throwing money at this thing, but I'm determined to fix this good awful problem.

 

[FrnkNsteen]

What rpm range does it vibrate in or is it all the time

Good question,... I was thinking the same thing..... Is it RPM based or Speed based? In other words, does it do it at a given RPM in every gear, or does it only do it in high gear up around the 65-70 mph mark you mentioned.

If it is RPM based (happens around 2300 rpm in every gear), focus on things forward of the transmission. If it is speed based (only happens at 65-70) focus on transmission and back (driveshaft, Diff, etc), or wheels and tires.... Anything not affected by RPM

 

[PP1RT]

Axle bearings?
Brake drums damaged? (Cracked,piece broke off)
Pinion bearing?

 

[moes]

out of round rear brake drums or out of balanced. We replaced a set of rear brake drums with new ones and they were causing a bad vibration at high speeds. One was causing the problem.

 

[SublimeSixpack]

Have you checked to see if you get the vibration @ 2300 RPM sitting still in Park or Neutral?

Also, are the new rear brake drums made by Centric?
Six or seven yrs. ago I bought and installed two new Centric rear brake drums on my '69 Super Bee and they were so far out of balance I couldn't use them. The POS's are still in their boxes and under one of my benches.

 

[6PKRTSE]

I chased a vibration like that at one time and replaced all of the same usual parts. Mine wound up being the harmonic balancer. Took off when I pulled the engine for a rebuild and it fell apart into two pieces when I set it on the shelf.

 

[PP1RT]

I chased a vibration like that at one time and replaced all of the same usual parts. Mine wound up being the harmonic balancer. Took off when I pulled the engine for a rebuild and it fell apart into two pieces when I set it on the shelf.

I would think that would be more rpm sensitive than speed related?

 

[Ski 61701]

As mentioned check your trans mount. Also how are your leaf springs? Does the rear end sag quite a bit? These 2 things can throw off your pinion angles enoug to give you grief.
Even though you've balanced your tires, you could still have a bad one, once the weight of the car is on them it loads the belts and once you get to speed vibration start.
Do you feel the vibration in the steering wheel or the seat?
Do you have a tach on the car? If so pay attention when vibration start. Put the car in park and have someone give it gas while you have your hand on rocker cover slowly rev it up to rpm and feel if engine vibrates, very well could be balancer or wrong torque convertor.
Lastly, find someone with a go pro camera start mounting it under the car looking at drive shaft, then look at wheels while driving, might get lucky this way too