In my case, the vibration is definitely NOT from the Gear Vendors O/D. I installed the GV late last year, but I have had this vibration in the car since the mid 90's. So definitely not caused by the GV.
The first "Hawk-Rod" resurrection, Roadkill style
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I don't know if I should curse a blue streak, or lay down in a fetal position and wimper a bit... 
So I got the rear from my 70 installed in the 73, installed the driveshaft, filled it, yada yada. The we put the shafts back in as per FSM, .008" to .018" play.
We also put new backing plates on the car (from a donor car). The ones on the car were quite worn where the brake shoes rubbed on the pads. See below where my finger is pointing.
Then we put it back together with all new brakes and the brake drums from the 70, in case there was an issue with the drums being imbalanced.
Result. Same *^%$@! vibration.
I am really at a loss here.
I don't know. The wind is out of my sails at this point and I'm running out of time. If anyone has any other ideas, I'm all ears...
So I got the rear from my 70 installed in the 73, installed the driveshaft, filled it, yada yada. The we put the shafts back in as per FSM, .008" to .018" play.
We also put new backing plates on the car (from a donor car). The ones on the car were quite worn where the brake shoes rubbed on the pads. See below where my finger is pointing.
Then we put it back together with all new brakes and the brake drums from the 70, in case there was an issue with the drums being imbalanced.
Result. Same *^%$@! vibration.
I am really at a loss here.
- This car has had two different balanced, blueprinted engines. No change in the vibration.
- This car has had two separate transmissions. No change in the vibration.
- The driveshaft has been balanced twice. Then it was shortened for the Gear Vendors O/D and balanced yet again. No change in the vibration.
- I just swapped the rear to a totally different rear. No change in the vibration.
- I checked the axles carefully. The bearings operate smoothly and in nice shape. No change in the vibration.
- I have had two different set of drums on the rear brakes. No change in the vibration.
- I have had two completely different sets of wheels and tires on the car. No change in the vibration.
I don't know. The wind is out of my sails at this point and I'm running out of time. If anyone has any other ideas, I'm all ears...
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Hawk, can you eliminate the iso bushings entirely to eliminate any flex? A lot of guys got rid of them back in the day. If not can you slip a leaf out of the spring pack so they fit better?
64fury74charger
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I don't know if I should curse a blue streak, or lay down in a fetal position and wimper a bit...
So I got the rear from my 70 installed in the 73, installed the driveshaft, filled it, yada yada. The we put the shafts back in as per FSM, .008" to .018" play.
View attachment 1267764
We also put new backing plates on the car (from a donor car). The ones on the car were quite worn where the brake shoes rubbed on the pads. See below where my finger is pointing.
View attachment 1267763
Then we put it back together with all new brakes and the brake drums from the 70, in case there was an issue with the drums being imbalanced.
Result. Same *^%$@! vibration.
I am really at a loss here.
The final potential (?): When I quasi-restored the car in the early 90's, I replaced the tired leaf springs with a set of Hemi leaf springs. I still remember that the ISO bushings in the suspension did not fit great, since the leaf springs were thicker than the original ones. Could this be placing the rear differential in a bad location and causing the vibration? I already tried to shim the rear a bit, but perhaps the shims were "overridden" by the ISO bushing and so the rear really didn't end up being shimmed at all?
- This car has had two different balanced, blueprinted engines. No change in the vibration.
- This car has had two separate transmissions. No change in the vibration.
- The driveshaft has been balanced twice. Then it was shortened for the Gear Vendors O/D and balanced yet again. No change in the vibration.
- I just swapped the rear to a totally different rear. No change in the vibration.
- I checked the axles carefully. The bearings operate smoothly and in nice shape. No change in the vibration.
- I have had two different set of drums on the rear brakes. No change in the vibration.
- I have had two completely different sets of wheels and tires on the car. No change in the vibration.
I don't know. The wind is out of my sails at this point and I'm running out of time. If anyone has any other ideas, I'm all ears...
If I am processing what you have said so far this vibration has been pretty much the same intensity or level even after different motor and transmission and now 3rd member and different drums as well. Sounds like you have eliminated the drive train and the wheel and tires as well as the GV unit and drive shaft.
Is there anything in the history of the car that may have resulted in the frame shifting from some seemingly minor incident?? You have pretty much eliminated all the “normal “ suspects and the frame may not be in proper alignment.
I am assuming that you are feeling the vibration in the seat and floor versus the steering wheel and that usually rules out the front areas. Just throwing things out there.
I saw this kit from Firm Feel. If I can get them in time, I might try to eliminate the ISO bushings and see if that helps. I don't think I can eliminate the ISO bushings without changing some parts.
I appreciate the brain storming. Obviously, I have failed so far to fix this...
Correct. It flat out CAN'T be the drivetrain components at this point. Angle, sure, but components - no way.
No accidents ever. This started after I "quasi-restored" the car. The only change I think could have anything to do with this issue is the leaf spring change I mentioned in #282 above.
Correct. No vibration at all through the steering wheel or the front area of the car. The car handles well, with no pulls, issues, etc.
Sorry, not quite sure what you mean about doing an on-car wheel balancing? I did swap out all the wheels for a different set of wheels from my 70 Road Runner (that run fine on that car).
No poly engine mounts. I don't remember about the trans mount. It could be polyurethane.
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hyde-park
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Quote: "Sorry, not quite sure what you mean about doing an on-car wheel balancing? I did swap out all the wheels for a different set of wheels from my 70 Road Runner (that run fine on that car)."
Here is a short vid on YouTube doing the rears on an earlier Vette:
Here is a short vid on YouTube doing the rears on an earlier Vette:
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We used to have a Bear balancer like that at my Dad's station in the late 60's. We had a Buick or Olds in one day which ran the speedo off the drivers front wheel. I think it spun at over 90 mph. Great because it balances the entire hub/ drum / wheel assembly. I don't think it would help you as you have already swapped out known parts.
I went out and pulled apart one side of my ISO suspension. Here is the assembly together as it would sandwich the leaf spring. The top plate is used for the rear sway bar, the bottom for the shock.
Here is an image with the sway bar plate moved out of the way.
Then the next image showing the two pieces that sandwich the leaf spring.
The bottom plate with the shock mount indexes in to the bottom bolt of the leaf spring as shown.
In turn, the top plate indexes in to the big cap at the top of the leaf spring as shown here.
It doesn't seem like it could really move around too much, but I wonder about the rubber pads and wear from age.
I also fail to see how the Firm Feel kit I showed a picture of in post #286 above could work. I see how it replaces the bottom shock plate, but I don't understand how it can fill big hole in the axle (see last picture on the axle flange). I do now want to try and get rid of the ISO bushings if I can to see if this fixes the issue.
Here is an image with the sway bar plate moved out of the way.
Then the next image showing the two pieces that sandwich the leaf spring.
The bottom plate with the shock mount indexes in to the bottom bolt of the leaf spring as shown.
In turn, the top plate indexes in to the big cap at the top of the leaf spring as shown here.
It doesn't seem like it could really move around too much, but I wonder about the rubber pads and wear from age.
I also fail to see how the Firm Feel kit I showed a picture of in post #286 above could work. I see how it replaces the bottom shock plate, but I don't understand how it can fill big hole in the axle (see last picture on the axle flange). I do now want to try and get rid of the ISO bushings if I can to see if this fixes the issue.
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They have simply used a thick washer of the correct diameter to fill the hole in the axle pad under the head of a new through bolt in the spring pack. The new bracket looks a lot like the stock earlier bracket. I'm not sure how that would work with your sway bar bracket.
As look at it more, I now see that - I was just out there looking at the pieces. I think I can make my own "ISO delete kit" pretty easily on the lathe at my father-in-law's shop tomorrow. It will retain the top plate, sway bar mount as well as the bottom plate. I just need to make appropriate shims (and possibly replace the bolts holding the leaf springs together).
Time to lose these rubber shims!!!
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Make a couple of extra washer/spacers so that if you add angled shims the washer will still engage into the hole. Looks like you will also need some spacers to take up space on the sides of the springs.
Good planning for the future! That's in the plan. I won't know until later today if I will use multiple washers or a single machined piece (per side). Either way, I will ensure it can engage the indexing hole even with angled shims.
Hmmm. I hadn't thought of that, but you make a good point. I can't slide the U bolts inwards due to the holes in the sway bar and shock plates. I obviously need to think about this some - thanks for pointing that out!
I think I would try adding some material to the rubber you have if you can't get replacement parts.
It looks to me like it's been compressed but not really deteriorated.
But of course I'm just looking at a couple pictures...
Maybe just cut some tire sidewall and make some inserts and sandwich it in there.
Seems like an easy thing to try before you change all the existing arrangement.
You can also get chunks of all types of plastic material from McMaster Carr but then you would need to machine it to duplicate/replace the rubber parts.
Just my thoughts.
It looks to me like it's been compressed but not really deteriorated.
But of course I'm just looking at a couple pictures...
Maybe just cut some tire sidewall and make some inserts and sandwich it in there.
Seems like an easy thing to try before you change all the existing arrangement.
You can also get chunks of all types of plastic material from McMaster Carr but then you would need to machine it to duplicate/replace the rubber parts.
Just my thoughts.
Or maybe these:
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I'm not familiar with the rear suspension on your car. Sorry I can't help you better.
Good luck Buddy! I'm watching and listening!
Good luck Buddy! I'm watching and listening!
The problem I have is that I don't have stock leaf springs. Years ago (1990's) I installed hemi leaf springs, so the OEM pads don't fit properly. I'm afraid it's time to ditch the pads.
My father in law doesn't think this will solve my vibration. As mentioned by another member, I could have a bent rear axle. Either way, I'm going to try the ISO delete first and then if that doesn't work check the axle to be sure it is straight. That's the only thing left at this point...
64fury74charger
Well-Known Member
Just my 2cents here in reference to the isolators I don’t see how those could create the vibration because they are really sandwiched in around the springs plus the weight of the car.
I am thinking something back there that is in motion is creating this vibration and those rubber isolators don’t turn or spin.
Still working on this with you.
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