I found a old Service Bulletin :Vehicle Vibration During Acceleration
caused by rear drive wheels camber angle
Torque Shake can be corrected by adjusting the rear wheel camber to 0 deg. from the normal specification of -1/2deg. +/-1/4 deg. I have vibration problems during heavy acceleration has anyone had any experince with this

 

What year was the Service Bulletin for and was it for a big block or what? Can you post a copy of it.

 

73 to 77 issued in 1977 I don't think I can link it but if you are intrested shoot me a PM Do you have vibs in your drive train? Mine does in high torque sitiations

 

I'm getting something like this, but I believe I've confirmed it's U-joint binding. I have a new VB&P rear spring to try to address it.

 

Let us know if that is your problem dstaley I'm still chasing mine

 

I found my vibration problem, and it wasn't in the rear suspension at all.

I rebuilt every bit of the rear suspension except for the wheel spindles, and all is working well in the back but the vibration was still there.

The root cause of the vibration turned out to be the water pump. I had bought a "short" aluminum water pump from Speedway Motors (made by Stewart). The pump had a 5/8" pilot, however the Corvette pump has a 3/4" pilot (for the fan clutch). I thought the studs would center the fan clutch- WRONG. The studs are not sufficient to keep it centered.

Once I found the problem I made a bushing on my lathe, but I had two other related problems- the timing cover interfered with the pump (quality problem with the pump, the little "legs" were shorter than they should have been) and the pulley hub was in the wrong place- spacers had to be used to move the pulley out for proper alignment. Once all the necessary spacers were made, it seemed like too much of a kluge job, so I abandoned the "wrong" pump and renewed my search for the right pump.

I knew about the Edelbrock one for far more $$$ than it is worth, then I found something new. GM is now making an aluminum pump- part number 19168604 which is available at Summit Racing and Jegs, and they can match the price at PartsZoneOnline.com for $109.25.

I bought it, painted it to match the engine, and it installed perfectly. No interference with the timing cover (there's a small but visible gap), the pulleys line up perfectly and the fan clutch is perfectly centered- no visual runout whatsoever. Temperatures are much more steady than with the old pump (the bypass line is not blocked as it was by a plug with the Stewart pump), the vibration is GONE, and all is well- a complete success story.

Conclusion- If you're using matching pulleys & brackets from an old Chevelle or Camaro, knock yourself out, I didn't go down that road. If you're working with Corvette pulleys & brackets, either buy the GM pump or the Edelbrock pump, and don't waste your time with the Chevelle "short" pump from the 60's. They are just incompatible with the Corvette pulley & bracket set.

 

you could be getting torque movement at the sombrero mounts.....vbp makes a kit of two aluminum discs that are a simple 10 minute install and helps out greatly..good luck

 

I have those that was plan A

 

dstaley, how much vibration you where getting ? can you describe it? felt it at the wheel or the entire car? Would it go away when push the clutch in or the rpms went down ?

I have some vibration at higher rpm`s (above 3k). I m hoping to install an electric fan this weekend, may be is the same problem you are having.

Thanks !

 

It was very noticeable over 3000 RPM, very distinct when I was "giving it the beans". I thought it was something rubbing, binding, or bumping when the engine was working hard, but it must have just been more pronounced when engine RPMs were high. I didn't notice it when not in gear but I'm pretty careful with the car and don't just sit there and rev it out of gear either.

The car is an automatic, so depressing the clutch wasn't an option. I didn't pick up on it when it wasn't running hard, but it had to have been there.

It's completely gone now, so although making a couple of those disc things is on my "to do" list, it's not a priority now since the vibration has been corrected. It's completely absent now.

I don't know how to quantify how strong it is other than put some accelerometers on it, but it was very noticeable when wt full throttle before it shifted (especially over 4500 RPM). There was no shaking at the wheel, it was in the seat and it was also audible.

If you have enough street (like a city block) for a quick test, take your fan clutch off and bolt the pulley on without the clutch and take the car around the block just to see if the vibration disappears. Get it back home quick so that it doesn't overheat, but it should be a useful test to see if you have the same root cause as I found in mine.

 

You are describing my problem, it works fine will 3kish rpms after that starts vibrating and doesnt get any better. In my car is more like a shaking than a vibration, not violent but it feels like if something was out of balance.

I ll give it a try, and be carefull of the temp. Also might just switch to an electric fan.

what is the disks thing ?


Thanks !

 

Disks:

 

what exactly do these disks do as compared to the big rubber bsuhings i have in there now?

 

It will stiffen the ride up for sure

 

They reinforce the rubber biscuits in case of failure. Honestly, with only a 7/16" stud to anchor them, unless the rubber is decomposed or the bent over fingers somehow come undone, there's not a ton of strength there, but they may help keep the fingers from bending over.

 

Hi, I took the mechanical fan out this weekend and it was not it, the car still vibrates after 3+k rpms. A friend who seems to understands cars more than i do, said it could be the flywheel and clutch.

 

I've seen this condition on automatics,but didn't care they weren't mine