Hello Everyone - I have a '69 H/O that has a rather pronounced vibration at speed (55mph +), and I cannot figure out the cause/fix. The vibration kind of "comes and goes" when going down the road at highway speed. The vibration never completely disappears but it does become less of a vibration for short/random periods of time. It has nothing to do with road surface given the vibration doesn't change when the road surface changes (e.g., go from asphalt road to concrete bridge). The vibration still exists when shifting into neutral and coasting at 60+mph. So, the vibration is speed related and not RPM related. The whole car vibrates and you feel it much more in the seat vs the steering wheel. The car was body off restored ~3 years ago and the suspension/ride-height is stock. I purchased the car with this issue and just assumed it was an out of balance wheel(s), bent rim(s) or bad tire(s). However, it's not a tire/rim situation. Below is a list of things we have already done but didn't result in a "fix". Any thoughts/ideas/etc are GREATLY appreciated as the problem is driving me NUTS. Also, I am happy to send the car to a skilled shop in the Midwest if anyone has a recommendation.

Work Completed

• replaced rims and tires (road force balanced)
• Replaced rear axle outer bearings
• replaced rear axles
• Replaced pinion bearing and carrier bearings
• Replaced U-Joints
• Balanced Drive-Shaft
• Put 600 lbs of weight in trunk, nothing changed when driving
• lifted the rear end of the car via the pumpkin and the vibration still existed at 55+ mph

 

Check rubber bushings, weak shocks, axle play, dragging brakes, tracking alignment, etc...

 

There are other threads on here regarding the use of a 'flange plate' when balancing this generation of Olds wheels. The flange plate centers the wheel using the lug holes (lug-centric), not the center hole (hub-centric) of the wheel. If measurements for balance and RFV were taken without regard to wheel centering, all results are inaccurate and should not be relied on.

Presuming proper wheel centering was accomplished, when the wheel/tire assemblies were "road force balanced" did they provide you with printed info about the measured radial-force-variation (RFV) for each?
I'd be curious to know what the numbers were for each assembly, and if they made any attempt to match-mount the tires to reduce RFV.
Did you replaced the tires because of their recommendation/findings of 'high' RFV on a previous set of tires? Were the new tires checked/verified, and what were the RFV numbers?

Lastly, there is a details screen that only dedicated, well trained, advanced users will access. Among other things, the details screen shows 1st, 2nd & 3rd order RFV. If the 2nd and/ or 3rd order RFV is higher than the 1st, the tire(s) is(are) the problem. Without checking that screen, problem tires are overlooked and problem-vehicles such as this are the result. 2nd and 3rd order RFV issues are uncommon, but should be checked especially in these situations.

Will be following along to see if this gets resolved.

 

Check for any part of the driveline/exhaust touching the body or frame, or a mount squished so badly there is metal to metal. That will rattle your fillings out.

 

I’d check driveline balance and driveline angles if it were mine.

 

I chased one across the country and back, literally. It ended up being the rear brake drums out of balance. $100 for a pair of China's finest off rockauto, and they even come painted!

 

Thanks for the prompt responses!! Regarding the tires/rims ... I swapped the tires/rims from my '70 442 onto the '69 H/O and the vibration didn't change. I also put the '69 H/O rims/tires on my '70 442 to see if the vibration would happen and there was no vibration. I think that eliminates the tires/wheels but happy to hear differently.
Regarding brake drums being out of balance ... that thought crossed my mind so I swapped the brake drums from my '70 onto the '69 and made zero difference.
Regarding shocks/bushings ... everything was replaced during the recent restoration. I also think shocks/bushings/etc would be eliminated given the vibration was still present when the car was lifted by the pumpkin and the vibration was still present (i.e., car was stationary and vibration was still present).
We've spent a decent amoutn of time with the car on the lift and we don't see anything worn/touching/etc as evertyhing appears "tidy" underneath, but anything is possible. I still need to check driveline angles and plan to do that this week. Guess i am not sure how to check driveline balance other than having the driveshaft balanced.
Please keep the ideas coming!!! Thanks in advance!!

 

Generally speaking, there was an old rule that if you felt vibration in your seat/butt, it was in the power train rear axle. If you felt the vibration in the steering wheel, it was a front end thing.

Recently, someone had a vibration problem and the drive shaft was balanced. It was discovered that the driveshaft had a run out problem from an end being welded on off center. Check the front yoke, the driveshaft behind the front U joint and the drive shaft forward of the rear U joint. You'll need a magnetic base and a dial indicator to check T.I.R.
I don't know if you could swap driveshafts between the 69 H/O and 70 442 to see if the vibration changes from one car to another. Good luck.

 

We did swap driveshafts from the '70 to the '69 and it made zero difference! PLEASE keep the ideas coming!

 

Thinking outside the box here base on experience. Have you verified that you DO NOT have a bent axle?

 

@SY2455 - i've typed it before but LOVE your syclone! Are you thinking bent rear axle housing? I've replaced the axles with new ones and it made zero difference but HAVE NOT replaced the housing (yet).

 

Put it on jack stands have someone bring it up to speed while you observe the driveshaft and wheels.

Back the rear shoes off so no contact with drums.

Ive had one brake caliper slider pin on one side hang up causing a vibe. F250. But same could apply here.

Ive heard of torque converters being out of balance. Will the car vibrate while in park at say 3000 rpms? Pull the flywheel inspection cover and watch for wobble.

 

@droldsmorland - thank you! The car has no unusual vibration while in park at 3000 rpms and thus I have mentally ruled out torque converter/flywheel. We did bring it up to speed while lifted via the pumpkin (to keep the suspension "loaded") and didn't see anything unusual. We could still feel the vibration. PS - where exactly is the "Land of Taxes"? Sounds like Minnesota to me

 

Find a shop that has a 4 corner vibration analyzer and someone who know how to use it. Then you can stop wasting time. Watch.

 

@Hammerdrop - honestly, never heard of such a thing but WOW. I am now in full "search mode" for someone in the upper Midwest that has the equipment/knowledge! Many thanks!

 

I wasn't thinking of bent housing. But I have purchased new axles and while the axle up to the wheel flange was straight, the flange was out of round by .175 and I had to go thru 3 more axles to get another good one.

 

I have nothing to offer, just dying to know what you find out, hope you get to the bottom of this!

 

That only applies to the 1975-up SuperStock wheels with snap-in centers. The 1968-74 style with bolt-in centers are hub-centric and do not have this problem. If this 69 H/O has the correct wheels, they are hub-centric.

 

I'll add this only because I don't think you mentioned checking it.

My rear pinion yoke allowed the u-joint an ever so slight side to side movement. The inside faces of each side of the pinion yoke were slightly worn. It was so little you could barely see a ridge. I replaced the yoke and the vibration is gone.

 

An approximate frequency would help. Higher frequency usually means higher speed. A driveshaft will usually produce a higher frequency than a tire.
At this point, everyone is just throwing darts. At some point, either the problem is found, or you go back to square one.

 

Also hunting a vibration issue on a 67 same as what you are describing. Have not swapped driveshaft yet and need to try a different set of rear wheels and tires... 2 other cars I have had similar issues, one had a bent wheel, other one a bad rubber coupled driveshaft.

 

As said above my 67 has a similar issue, I dont know if I fixed the issue yet but my pinion yoke was damaged at the ears where U bolts attached. Appears someone beat on them pretty good with a hammer. It has been replaced but havent road tested yet.

 

FWIW I originally narrowed it to that by refacing the inside of the yokes with JB Weld. The vibration would go away until the JB Weld wore off.

 

I scrolled back through and did not see tailshaft bushing in the trans.

 

That ATS Vib diagnoses equipment in the above YouTube video Hammerdrop is VERY cool.
Zero guessing on the vibe source location and reducing the tendency of propelling unnecessary parts at the problem.

 

I know you said you replaced the pinion bearing, but have you grabbed the rear U-Joint/yoke and checked for excessive play in the pinion?
Same logic can be applied at trans yoke sleeve bushing as mentioned above. There should be some up/down there but too much is not good.

 

What is your driveline angle in relation to the pinion angle?

 

Try flipping the driveshaft 180 degrees on the yoke.

Try “reclocking” the torque converter.

Mske sure the exhaust isn’t grounding out on the frame somewhere. Keep in mind the exhaust can “grow” and move around a little when it gets hot.

 

If you want to be crazy, pull the driveshaft, stick a plug on the output shaft, and hook a strap around the main frame horn under the engine. Have someone tow you to highway speed early one Sunday. Engine in neutral, running for brakes and steering, but you probably could shut it off for a bit to listen.

 

Thanks Guys! The car goes in tomorrow for vibration analysis as @Hammerdrop suggested. I truly appreciate all the suggestions/insight/knowledge, and I will report back the findings! Fingers crossed they can isolate the issue!

 

Update: the shop that said they had the vibration analysis equipment did not have any advanced equipment. So, I am back to hunting for a shop with the correct vibration analysis equipment as suggested by @Hammerdrop .

 

Maybe you would have better luck looking for a mobile diagnostic business. Diagnosis is their bread and butter and they are sometime called by shops to figure out problems the shops can't or won't take the time to solve. Body shops might use them to figure out crash related electrical problems too.

 

Try contacting ATS, and see if they'll tell you who they've sold equipment to. If they only sell to reps, find out who the rep is for your area.

 

Its been a few months has the issue been resolved?
May try removing the rear drums and flip them over bolt them back up to the axle and check runout on brake surface.
Check runout of front rotors just for piece of mind as well.
Another thing to check is your shocks a shock may have a dead spot in it
Im sure someone mentioned it above what are your drive line angles?
Trans mount in good shape?

 

I had a similarly frustrating issue and a friend of mine suggested I swap another A-body differential in just to try. The swap only took a few hours and the problem went away. I sent my original diff to Moser and when it was returned, it was quiet.

 

Transmission mount ??

 

Update - i've not been able to locate a shop using the ATS vibration equipment anywhere in the midwest. So, my plan is to purchase the equipment and do the diagnostics myself. However, it's winter in Minnesota and so I will not be doing any testing for the next several months. Having said that ... keep the ideas coming and I will definitely post any updates once the roads are clean of salt.

 

Maybe put it on a dyno and look it over as you run it through the gears.

 

Front wheel bearings lubed and torqued correctly? Steering box slop? An auto mechanics instructor advised once to put the car on asphalt and look at the suspension joints from underneath while someone turned the wheels back and forth. Any worn or loose items would be visible.