Technical Good Vibrations - Beach Boys had them but I don't!

On my '56 Chevy my 45-60 mph vibration was due to the driveshaft yoke being shoved into the trans too far, a result of the PO lowering the hell out of the back. I raised it 1" and the problem went away. Later I installed the Danchuk 3/4" forward motor mounts to get the correct amount of working distance.
This thread is a treasure trove of good ideas and info, I may take it out for the moving fingers, giggling balls test tomorrow. The '56 that is.

 

"She's real fine my 409" wedge.

 

That's a neat tool but isn't it on the wrong u joint cup?

 

^^^^^ That's why he thinks it needs a wedge.

 

RIP, Hal Blaine..Now back to our program

 

I chased a Vibration On my 39 for some time. Turned out to be bad GM rotors.

 

Danny have you fixed the problem?

 

Anything that rotates, including brake drums, rotors, etc. can cause it, including driveline angle. I had a pair of out of balance brake drums once that drove me crazy until someonennhere finally suggested it. Sure enough, they had no balancing weights on them.

This is assuming the vibration doesn't occur when the car is stationary. I also had a slight vibration in my steering caused by having solid u joints in the steering linkage. Borgeson makes a vibration reducer to fix that, as well.

 

John, I haven't yet I'm still gathering information. HRP

 

The vibration will have characteristics.
Related to a condition:
Engine rpm- reguardless of wheel speed
Road speed reguardless of engine rpm
Road speed reguardless of gear
Only While braking
Gone only whike breaking
Only upon coasting
Only upon acceleration.

I haven't driven this vehicle but so far Danny's description is vibration only upon acceleration. The suspicion should be within the drive line.
Then you drill down from there.
Acceleration from what speed, gear, rpm, blah blah blah. Eliminate non moving parts, then look at the pinion and everything it does-that's a lot

 

With it more pronounced on accel I would verify pinion angle first.

 

I would check drive line angle real close

 

How does a fella check his drive line angles when under acceleration?

 

Plexiglass floorboards.

 

Or a lack of floorboards, fortunately or unfortunately depending on your point of view they are quiet solid so I can't see through them. HRP

 

You put a mojo on it when you changed your mind from semi custom to hot rod. Ain;t nothing gonna fix it short of a trip to see Miss Rudolff

 

I don't hang with the cool kids so my lingo is lacking, what or who the heck is Miss Rudolff? HRP

 

Look up Mudbone and the voodoo lady by Richard Pryor on youtube

 

Thoughts......loose u-bolts could be causing the spring pads to rock under acceleration, changing pinion/joint angle to an extreme. The harder you accelerate the more severe the vibration.

 

Rear trans mount, torque converter bolts loose, tires out of round, balance.

 

First: HRP thanks for all you do on this forum.

allow me to guess from hundreds of miles away....

1.Cracked flex plate
2.Hogged out wheel lug holes
3.Weird tire issue (yeah, it happened to me -same symptoms, inner belts/cords were delaminating)

 

Ever since I heard the story of a guy that hung under a vehicle to see what was happening while in motion and got wound up in the drive shaft. A camera would be safer.

 

While I haven't had a chance to dive into the problem I can answer some of the diagnostics, the tires & wheels are new and have been balanced, the rear drums have been turned and new shoes installed. HRP

 

That's scary

Don't worry, there is no way on God's green earth I would get under a car running and in gear. HRP

 

That's spot on. We used to use these same or similar conditions diagnosing ride disturbance complaints on class 8 trucks. We had one tractor that we corrected many obvious issues on, to no avail, until we drilled down and found that the owner/operator had the clutch replaced. Dealer replaced the assembly for him again, but the vibration stopped when he took it back again and had the flywheel surfaced and balanced. Dealer didn't think it was necessary.

 

There have been several threads on here about setting Drive line angle. Check them out and see where you are for angle.

 

Sorry, I was just here for the Beach Boys video, carry on...

 

Was the vibration already there and change (or stay the same) with the removal of the lowering blocks? Or did the vibration start with the removal of the lowering blocks?

 

Long overdue update, I have been so busy helping Dave with the interior of my old beater that I have kind of neglected , no I have ignored the problem thinking it would take care of itself, no such luck the problem remains.

I had to replace a tire on my daughters car yesterday and I drove the coupe to the tire shop and on my way home stopped at a friends garage and ask him could we put the car up on the rack and check the drive shaft, he was about to do a oil change on a customers car but since they were not there he said sure.

We got the car up and I reached up and tried to turn the driveshaft and there was a slight clunk, the universal joint at the rear is bad.

We didn't have time to pull the driveshaft but that is planned for this weekend. HRP

 

Lostone is giving you great advice here to help isolate the issue. You need to determine if it is drive train related, or suspension related. So, like he said, run it up to the speed that it is vibrating, then throw it in neutral (be care not to hit reverse). If it still vibrates, it's most likely suspension/tire related. If it stops the vibration when throwing it into neutral, then it's most likely drive train related (motor mounts, tranny mount, drive shaft balance).