I’d get a dial indicator and check axial and radial runout.  Pull the wheels off and check at the axle flanges/ brake disc or drum.  Could be out of whack from an old accident.  Even a stray hammer blow to the edge of an axle flange can keep a drum/rotor from laying flat on the axle flange.  Debris, crappy tolerances, damage.  Doesn’t take much at the axle flange to translate into something noticeable at the wheel / tire.

Last edited by Bentworker (12/05/2022 10:36 PM)

Bentworker wrote:

I’d get a dial indicator and check axial and radial runout.  Pull the wheels off and check at the axle flanges/ brake disc or drum.  Could be out of whack from an old accident.  Even a stray hammer blow to the edge of an axle flange can keep a drum/rotor from laying flat on the axle flange.  Debris, crappy tolerances, damage.  Doesn’t take much at the axle flange to translate into something noticeable at the wheel / tire.

You haven’t picked up on the earlier remnants of this thread. My car has had different axles, wheels, brakes, rear end housings and any other component you can dare to mention, all changed multiple times. Now, maybe the vibration was caused for fifteen years because something was THIS WAY and the last fifteen years caused by it being off THE OTHER WAY.  Things have been changed so much the baseline is long gone.

Bentworker wrote:

At least checking runout is cheap and easy.  Would take tens of minutes. 

Sometimes troubleshooting turns into reproving that the sky is blue.

I guess I am just tired of chasing the problem.  I need to get scientific about it. I understand there is a phone app for $5 that can measure vibration frequencies. Then just figure out what is turning that rpm frequency at 80 mph.

Part of the problem is I have to drive thirty minutes to get to a road where I can drive at high speed.  It just ties up too much time.

Nos681 wrote:

Did this happen without subframe connectors?

Both normal length and MS extended length?

IT HAS ALWAYS DONE IT. BEFORE CONNECTORS AND AFTER.

Can you feel any of this vibration in park at various RPM’s?

I HAVE NOT SUCCEEDED AT GETTING THE CAR TO 80 MPH IN PARK.

MS wrote:

Nos681 wrote:

Can you feel any of this vibration in park at various RPM’s?

I HAVE NOT SUCCEEDED AT GETTING THE CAR TO 80 MPH IN PARK.

😂😂😂

Can you feel the vibration from back seat at 80 mph? 😁

Last edited by Nos681 (12/10/2022 6:58 AM)

MS wrote:

Bentworker wrote:

At least checking runout is cheap and easy. Would take tens of minutes.

Sometimes troubleshooting turns into reproving that the sky is blue.

I guess I am just tired of chasing the problem. I need to get scientific about it. I understand there is a phone app for $5 that can measure vibration frequencies. Then just figure out what is turning that rpm frequency at 80 mph.

Part of the problem is I have to drive thirty minutes to get to a road where I can drive at high speed. It just ties up too much time.

I’ll add my vibration occurred before and after:
.  I changed to the MII front suspension (which included different spindles and all disc brake components)
.  I installed a new driveshaft that was checked for straightness and balanced.
.  I had the rear narrowed and new axles installed (with the same rear disc brake components)
.  I installed subframe connectors.
The only thing that seemed to reduce some vibration was installing a 2.5” exhaust to replace a 2”.
 
Although I’m also tired of chasing these vibrations, I’m going to get the rear end (9") rebuilt with new gears over the Winter and will post results.

 

Just additional follow up on my Car's set up, I had the car on a lift this past weekend and the motor 
/trans are at 2.7, and the drive shaft was .7, and the pinion was 2.1, but down in the wrong direction. Now I added shims to rotate the pinion up and is now 2 degrees up. But the drive was so flat, that rotating the pinion up now has the drive shaft rising up towards the rear diff/pinion.

I believe MS is correct in the fact that the common issue is ride height. Like Steve, I love the stance and the way my car sets, but I may be willing to give that up for the lack of a vibration. The problem seems to be a combination of the T-5 setting lower and the rear differential being located hight into the body at the lower ride.

Information that would be nice to compare is those that truly do not have any vibration and run a T-5, what is the measurement between the rear wheel center cap and the fender lip. It won't Suprise me if everyone without a vibration set a couple inches higher than those of us who do have the vibration.



I bet this one doesn't vibrate

BobE wrote:

BILLY WALTON from GEORGIA wrote:

I have slammed a few up in park over the years after chasing cars well over 100 … it makes a loud clicking sound as you stop.

LOL
 

Hey, Wasn"t there a Barney Fife episode about that??
 

kardad wrote:

Just additional follow up on my Car's set up, I had the car on a lift this past weekend and the motor 
/trans are at 2.7, and the drive shaft was .7, and the pinion was 2.1, but down in the wrong direction. Now I added shims to rotate the pinion up and is now 2 degrees up. But the drive was so flat, that rotating the pinion up now has the drive shaft rising up towards the rear diff/pinion.

I believe MS is correct in the fact that the common issue is ride height. Like Steve, I love the stance and the way my car sets, but I may be willing to give that up for the lack of a vibration. The problem seems to be a combination of the T-5 setting lower and the rear differential being located hight into the body







at the lower ride.

Information that would be nice to compare is those that truly do not have any vibration and run a T-5, what is the measurement between the rear wheel center cap and the fender lip. It won't Suprise me if everyone without a vibration set a couple inches higher than those of us who do have the vibration.



I bet this one doesn't vibrate

I'm not running a T5 but rather an AOD.  However mine also has the pinion yoke higher than the trans yoke.   This worried me a bit until I came to the conclusion that up or down, complimentary angles on the U-joints are complimentary angles.  I honestly don't think the drive shaft knows the difference.
Will try to get some  angle reads tomorrow but the Heap is anything but HiGH.

A friend of mine bought a new T5  series for his vett. The installation instructions says how to measure center line at the input shaft and to measure and shim the bell housing to the engine and the transmission. I never to know that nore did I do it

I’m trying, It was new info to me.

I’m to lazy to go back and re-read this thread and I can’t remember if you have tried a “Fluid damper” chasing the vibration.
The silicone filled damper seems to self adjust throughout the different rpm ranges.
.