MS wrote:

Sounds like mine at 74 mph. Been chasing it since 1993.
Been through different engines, transmissions, driveshafts, rear ends, wheels and brakes.

I think a 1,000 watt mega-stereo is the only answer.

Or, if you figure it out, please let me know!

When I worked for Ford Mtr., in the mid eighties, we worked with a resonance roar that engineers hung a large tuneing weight on the tailshaft of the transmissions to cancel out the moan.  I don't know if it was all engines or specific ones, but there isn't a mounting boss on the Top Loaders to try that plus I don't know where to get one to try.  I guess I may just have to spin the motor up to 3400 rpm and hope I don't run into radar.
 

I put one of those 8lb (I think) weights on my then FMX thinking it would help my similar noise/vibration deal without success. My 69 is lower than most, but I never had a clearance issue going over speed bumps or driveways with the weight installed.

Last edited by rpm (10/19/2018 10:30 PM)

The problem with those tuning weights is that once you go away from the stock configuration you can't expect them to do anything.  They were tuned to very specific frequencies.  Once you swap gears, lower the car, even just change the wheel/tire setup you've gotten outside the bounds under which they were designed.  The 5.0s all had a chunk of metal hanging off the rear end for that purpose.  Over the years we took them off, put them on, all trying to "fix" harmonics or vibrations and it never worked because the cars were all modified.

MS is right IMO, but it can be done with as little as 500 watts

My understanding is that those weights, and the "dogbone" that all 8.8 equipped Fox and SN95 Mustangs had, were there to combat some kind of a harmonic caused by the resonate frequencies of the u-joints and the gears with which those cars came equipped (usually 2.73s).  I've read engineering documents from Ford that claimed the dogbone actually prevented premature u-joint failure due to this situation.  Consensus is that swapping to numerically higher gears effectively negates the need for the dogbone, because the resonate frequency of those gears and the u-joints no longer coincide at highway speeds. 

The real issue I see with them on the Fox and SN95 car is decades of street use, road salt, etc.  Every one I've seen the hardware is about ready to snap and the bushings are shot, meaning its not doing anything anymore anyway.  Based on that and the preceding I am opting to delete the dogbone on my '89 GT project.  I've stepped up to 3.73 gears when rebuilding the rear in that car as well. 

rpm wrote:

6sally6 wrote:

MAN that's a good look'in Mustang!!^^^^^^^^^^
jus say'in
6s6

I don't care what any of the guys say Mike, you do have good taste
 

Yep....next to a 63 split-window.......69Mustang is my favorite body style!  (sorry!)
6s6
 

Last edited by 6sally6 (10/24/2018 10:15 PM)