FYI FORD - MustangSteve's Ford Mustang Forum
The Internet's Most Knowledgeable Classic Mustang Information
IF YOU HAVE A QUESTION ABOUT CLASSIC FORD MUSTANGS, YOU HAVE COME TO THE RIGHT PLACE!
MustangSteve has over 30 years of Mustang experience, having owned 30 of them and restored several others. With the help of other Mustangers, this site is dedicated to helping anyone wanting to restore or modify their Mustang.... THERE ARE NO DUMB QUESTIONS!!!!!
Visit MustangSteve's web site to view some of my work and find details for:
FYIFORD Contributors' PICTURES - Power Brake Retrofit Kits for 65-66 Stangs - Classic Mustang FAQ's by MustangSteve - How to wire in a Duraspark Ignition - Mustang Ride Height Pictures and Descriptions - Steel Bushings to fit Granada Spindles to Mustang Tie Rods - Visit my EBAY store MustangSteve Performance - How to Install Granada Disc Brakes MustangSteve's Disc Brake Swap Page - FYIFORD Acronyms for guide to all the acronyms used on this page - FYIFORD Important information and upcoming events

You are not logged in. Would you like to login or register?

10/06/2022 4:21 PM  #1


Chasing that 80+mph vibration

66 fastback, aluminum Dart 427, TKO 600, 9” 3.50:1 rear end. 2.5” exhaust. Walker quiet flow mufflers. 13” Cobra front discs, 13” 2019 Mustang GT rear discs. Aluminum 3” driveshaft. Aluminum 17” wheels.



Carefully measured all angles with digital gauge. Entered numbers into Spicer’s website. It says any number less than 3 degrees is good.  Heavy growl at 80 mph or more, accelerating, decelerating or steady cruise.

I have finally admitted that a cruise control set on 78 mph is the final solution.


Money you enjoy wasting is NOT wasted money... unless your wife finds out.
 

10/06/2022 5:42 PM  #2


Re: Chasing that 80+mph vibration

I have been chasing the same vibration for years and it drives me crazy. Like most, everything was fine with the stock drivetrain. Then as soon as I decide to start making things better, we’ll you know.

My vibration starts about 75 and is bearable until about 80, and then just gets progressively worse, and you can not drive out of it. At about 95-100 it feels like something is going to fly apart.

5.0(331), T5 (2.95 first gear), Explorer 8.8 with Trac loc and 3.73 gears. 2006 MS Mustang front disc, Explorer rear disc. 17” wheels. First had the Explorer aluminum driveshaft, second a new steel driveshaft.

The Explorer 8.8 was narrowed by shortening the long side to center the dif.

I will get my Trans, Driveshaft, and pinion readings and post them to see how they compare. I have adjusted the pinion with shims multiple times and at times it seems to change the speed at which the vibration starts but never gotten rid of it.

I have tried multiple trans cross members and mounts. I have tried raising the motor as well with shims.

I would need to add cruise and set it slower, at 70 everything is extremely smooth.

 

10/06/2022 6:32 PM  #3


Re: Chasing that 80+mph vibration

So much for me thinking about trying an Exploder rear end!


Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     Thread Starter
 

10/06/2022 8:05 PM  #4


Re: Chasing that 80+mph vibration

Presently;
5.0 EFI, AOD, HiPO manifolds, 2"  Quiet flow mufflers and pipes with no crossover, 17" Cragar wheels, 12.5 GT front discs, 11.25 ish Explorer rear discs on narrowed (by me) Explorer 3.55 Limited Slip rear axle.  No vibration from O to 100+ mph.  No constant drone though I though I might have heard some during a strong cross wind.  No gear howl though I seem to hear some kind of "ringing" which no one else hears....Hmmmm, must be in my old head.  This condition has existed through two different home brew transmission mounts, with the AOD and 4R70W and back to the AOD.  Driveshaft is regurgitated from the 89 TC donor.  Exhaust has been changed from 2,25" with shortened Flowmaster 50's to the present setup with no change other than quietness.
Can't remember the exact the transmission and rearend angles but I seem to recall they were more than a couple of degrees....like 5 or so.  Maybe too close to zero causes a problem with the U-joints, who knows.
Back in the 8" days it did have a howl that came in around 45 and stayed all the way up.  Also had a minor vibration that came in at 70 but nothing like what MS is putting up with.  The 8.8 solved both problems. 
Wish I could come up with something specific to offer.  I guess I just dumb-stumbled into a mix that works.

BB1
 

Last edited by Bullet Bob (10/06/2022 8:06 PM)


"you get what you pay for, good work isn't cheap, and there are NO free lunches...PERIOD!"
 

10/07/2022 9:36 AM  #5


Re: Chasing that 80+mph vibration

MS,  I came across this article that provides some insite and may be worth checking.  https://www.dragzine.com/tech-stories/pinion-offset-guide-and-how-to-with-chassis-engineering/

 

Last edited by Glens 1965 50 (10/07/2022 9:36 AM)

 

10/07/2022 5:58 PM  #6


Re: Chasing that 80+mph vibration

Thanks, Glen

No doubt that can cause issues. I think they have a typo stating the 9” rear end is offset 15/16”.  It is actually 5/16” as shown in their picture.

The previous housing I had custom built for my car had the pinion centered. Same vibration!  But, I am going to carefully measure everything to see if some improvement could be made on my car.  I custom made my tranny crossmember and centered the tailshaft between the frame rails. Maybe that was wrong.
My rear axle currently in the car has the 5/16” pinion offset like stock. I need to measure everything and maybe I will need to reposition the crossmember sideways. As the article states, the car is not going to be happy unless it is RIGHT.   I know the vertical angles are correct. I just need to get the horizontal component dialed in.

This 5/16” offset of the pinion brings to mind that the Mustang rear ends are ALWAYS put into the car with the rearend offset to one side… by 5/16”!  You will discover this when installing larger rear tires and find that you have 5/16” more clearance on one side.  I wonder if that was Ford’s design to align the driveshaft.

Does anyone know if/how much classic Mustangs have the engine offset to the passenger side?   It seems that is the starting point to get this right.  I will find out when I start measuring.

Last edited by MS (10/07/2022 6:25 PM)


Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     Thread Starter
 

10/08/2022 10:02 AM  #7


Re: Chasing that 80+mph vibration

I can add that my TCI front crossmember that is still not installed in the car..  All mounting holes and width have the engine centered in the engine bay and does not 5/16" offset.  I plan to go BS with another local hot rod shop and see if they have any insight on the matter.  FWIW

 

10/08/2022 10:14 AM  #8


Re: Chasing that 80+mph vibration

My Jag rear is smoooooth!!!!! I've only had it to 157 MPH though.

 

10/08/2022 2:17 PM  #9


Re: Chasing that 80+mph vibration

Eliminate  ALL rubber biscuits in the trans AND engine mounts! (Maybe solid mount the seats too!)
Sure it will continue to vibrate butt.......so many possibilities you'll just stop worrying about it!! 
Sirius-lee........ When the 69 is on the road. ...see if it vibrates at the same speed. IF not....compare the dimensions between the two cars. IF it does...put it back to stock set-up and see what happens....then copy it on the 66.
6sally6


Get busy Liv'in or get busy Die'n....Host of the 2020 Bash at the Beach/The only Bash that got cancelled  )8
 

10/08/2022 2:49 PM  #10


Re: Chasing that 80+mph vibration

One time I mounted one of my wireless cameras under a car to chase a vibration. I started out with it mounted so I could see front to back sort of off to the side a little. I could see the length of the drive shaft and see a bit of the tranny tail housing. I sat in passenger seat and let son drive. It was scarry. The rear axle got real excited and the motion was not just up and down. There was enough force that the rear leaf springs were allowing the axle assembly to rotate back and forth around the axle centerline. Since then I have used the camera method a lot. A GoPro works good. I have also used my endoscope. One I did ended up being the engine mounts got in a rythum that put a force just wrong for the rear springs. New mounts fixed it.

 

10/08/2022 7:11 PM  #11


Re: Chasing that 80+mph vibration

I wonder if a person could get a hold of a vibration meter, run it on the hiway, then run it again on a dyno.   
 
Wouldn't that eliminate if its in the drive train or the body?


If multiple things can go wrong, the one that will go wrong will be the one that causes the most damage.
 

10/09/2022 3:11 PM  #12


Re: Chasing that 80+mph vibration

I did the accelerometer thing once on my race car to find a vibration source. Worked great, but took a fair amount of high dollar equipment I had access to from work. Camera did same job a whole lot easier.

 

10/09/2022 7:11 PM  #13


Re: Chasing that 80+mph vibration

I've been needing an excuse to invest in a Go-Pro.
 

 

10/10/2022 2:33 PM  #14


Re: Chasing that 80+mph vibration

Are there any shops in your area, where you can take the car and put it on a dyno for them to source the vibration?


1964-1/2 D Code Coupe - 289 V8, 4 Speed Toploader, 3.00 ratio rear, Autolite 4100 Carb, 15" tires, Pertronix ignition
 

10/10/2022 7:32 PM  #15


Re: Chasing that 80+mph vibration

6sally6 wrote:

Eliminate  ALL rubber biscuits in the trans AND engine mounts! (Maybe solid mount the seats too!)
Sure it will continue to vibrate butt.......so many possibilities you'll just stop worrying about it!! 
Sirius-lee........ When the 69 is on the road. ...see if it vibrates at the same speed. IF not....compare the dimensions between the two cars. IF it does...put it back to stock set-up and see what happens....then copy it on the 66.
6sally6

The difference is ride height. The 66 sits low, and I refuse to change it!


Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     Thread Starter
 

10/11/2022 3:07 PM  #16


Re: Chasing that 80+mph vibration

Chassis dyno sounds like a REALLY good step in the right direction !
6s6


Get busy Liv'in or get busy Die'n....Host of the 2020 Bash at the Beach/The only Bash that got cancelled  )8
 

10/12/2022 10:55 AM  #17


Re: Chasing that 80+mph vibration

None that I know of around here. Maybe San Antonio or Austin


Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     Thread Starter
 

10/12/2022 6:48 PM  #18


Re: Chasing that 80+mph vibration

MS wrote:

None that I know of around here. Maybe San Antonio or Austin

 
As many motors you build Steve, seems like you should buy one.


Bob. 69 Mach 1, 393W, SMOD Toploader, Armstrong  steering, factory AC.
 

10/12/2022 10:58 PM  #19


Re: Chasing that 80+mph vibration

Steve, I can't remember if you've tried switching wheels, would be worth the time if you haven't.


Bob. 69 Mach 1, 393W, SMOD Toploader, Armstrong  steering, factory AC.
 

10/14/2022 9:22 PM  #20


Re: Chasing that 80+mph vibration

Bearing Bob wrote:

Steve, I can't remember if you've tried switching wheels, would be worth the time if you haven't.

Every mechanical part on the car has been changed to something else at least three times


Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     Thread Starter
 

10/15/2022 8:14 AM  #21


Re: Chasing that 80+mph vibration

I just seen something about what the color dots are there for on new tires. I have to pay more attention to them since I dismount & mount and balance my own. Just never knew that

 

10/15/2022 9:22 AM  #22


Re: Chasing that 80+mph vibration

red351 wrote:

I just seen something about what the color dots are there for on new tires. I have to pay more attention to them since I dismount & mount and balance my own. Just never knew that

Well, if that's true, the tire stores aren't following the "dot" theory....

 

10/16/2022 10:29 AM  #23


Re: Chasing that 80+mph vibration

red351 wrote:

I just seen something about what the color dots are there for on new tires. I have to pay more attention to them since I dismount & mount and balance my own. Just never knew that

I understood that the ‘dots’ on tires found on new cars indicated the ‘heavy’ spot on the tire.  The dots are than placed 180 degrees opposite of the tire valve.  From my limited inspections, I have found that where there are dots, they are opposite the tire valve.  I haven’t seen these dots on replacement tires. 

 


65 Fastback, 351W, 5-speed, 4 wheel discs, 9" rear,  R&C Front End.
 

10/16/2022 4:24 PM  #24


Re: Chasing that 80+mph vibration

I recently changed tires on my Pilot.  the circles were all right at the valve.  And my tire dealer has been there for a couple of generations.  Lots of experience.  The tires have virtually no weights on them.  Can't remember offhand what brand.


Original owner - 351w,T-5, 4whl disks, power R&P
 

10/16/2022 7:05 PM  #25


Re: Chasing that 80+mph vibration

MS, if I am reading your readings right, your trans. is down 2.9 and your rearend is 2.7 down.  If that's the case, that will never work correctly imho.  First of all I'm no mechanic and all I know about driveline angles is what I read and what a friend of mine, who worked for Ford, told me. This friend would set the angle between tandem axles on heavy duty trucks. Yes, even that short little driveshaft had to be angled correctly. I know I have read your posts about this problem that won't go away for quite some time now.  Maybe you have tried this, I can't remember.  I would raise the trans. as much as I could and then tilt the rearend up...if the trans is tilted down say 1 or 1 1/2 then you want the rear tilted up 1 or 1 1/2.  The lines extended out from each should be parallel, they should never intersect which is what I'm reading on your angles. If I'm wrong about this please forgive my rambling on, and please someone correct me if so.  MS it would be nice if you posted a side view drawing of your angles.
 


66 Vert.  4.6 DOHC, 4R70 Auto, Heidt's M2 frontend
 

Board footera


REMEMBER!!! When posting a question about your Mustang or other Ford on this forum, BE SURE to tell us what it is, what year, engine, etc so we have enough information to go on.