I need some help – Mental but I only care about solving my cars woes now. Most sane people would have thrown in the towel but I have a disorder in not letting a problem go unsolved and it is really bugging me.
2008 V6 Mustang, T5 trans, Astro gear cluster & shaft with 0.8 fifth gear, 8.8 rear end, Torsen T2, 4.1 gear with a Moser 1350 yoke. This vehicle was setup to run in NASA TT events & not completed because of driver & driveline problems.
I swapped the trans, drive shaft, flywheel, pressure plate and rear end at the same time. At a driveshaft rotational speed of 5035 RPM - 95 MPH, we had heavy driveline vibrations.
I pulled the driveshaft out and had it rebalanced. It was out of balance. The vibrations remained - Now kicking in at 5300 RPM – 100 MPH.
I replaced the upper rear control arm with an adjustable one (Heim Joint chassis, stock rubber in differential) and new lower control arms (Stock length with poly bushings) to improve pinion angle.
Now the pinion angle is within 1.5 Degrees – No more adjustment in the upper control arm- not much change.
I was given an aftermarket engine cradle to drop the engine 0.5” and I shimmed the transmission up .1875” - Now the pinion angle within 1.0 degree. I spun the drive shaft myself on a friends machine using dial indicators to check for run out. No run out at 3500 RPM. Vibration now kicks in at 5560 RPM – 105 MPH.
Purchased a helm-jointed rear adjustable lower control arms. I was able to adjust the pinion angle to 0.0 degrees but the lower control arms were short and the bump stops didn’t line up. Pinion angle now 0.0 degrees at ride height (Rear pinion parallel with trans). The vibrations are now at 5830 RPM – 110 MPH.
Purchased a modified part to lengthen the upper control arm and I re-adjusted the lowers to stock length – Stile 0.0 Degrees pinion angle at ride height – Pinion is parallel / in line with trans at ride height.
I called a very good friend of mine to ask for his opinion. He wanted the car because he was having similar problems with a customer’s / project 2006 V6 Mustang. He swapped parts between the 2 cars – no luck. He checked the rear end pinion, ring gears and axles for run out and back Lash on my car with dial indictors– They looked great.
Both cars had drive shafts from the same manufacturer. He pulled both drive shafts and went to his go to Drive shaft shop.
My friend gets a call from a writer / friend looking for filler space for his series in car Magazine. I worked with the writer years ago when he wrote for magazines doing various articles for cars I worked on. He’s a good guy so I told my friend they could use the car for the needed filler space. The new drive shaft shop makes a 4” drive shaft – very nice unit. My friend puts the driveshaft in his car and tests it up to 140 MPH - 6500 RPM shaft speed (27” tire 3.73 gears) - No noticeable vibrations (Soft rear suspension bushings). They call it a day and the article went to print.
My problem 26.2” tire 4.1 gears. I stile see heavy vibrations with the 4” driveshaft at 115 MPH 6049 RPM shaft speed (Solid bushing rear connections - Heim joints ) which are not masking the problems but possibly enhancing them.
I pulled the trans, flywheel and pressure plate and replaced them with loaners just to make sure they were not contributing to the problem - No change in harmonic vibrations.
I purchased a driveshaft 3.5” OD using a CV Joint instead of the common commercial slip joint - Very nice driveshaft but no change. I installed hub centric rings for my lug centric wheels – no change.
I tested at Auto Club / Fontana Speedway a few weeks ago and ran the car up to 125 MPH to see if the harmonic vibrations would cancel out – 6575 rotational shaft speed. The vibrations got aggressively worse.
The car has been sitting since Auto Club – I am at a loss as to how to correct the problem. This has to be basic – What am I missing?
I’m open to all suggestions – Any & all advice would be appreciated.
2008 V6 Mustang, T5 trans, Astro gear cluster & shaft with 0.8 fifth gear, 8.8 rear end, Torsen T2, 4.1 gear with a Moser 1350 yoke. This vehicle was setup to run in NASA TT events & not completed because of driver & driveline problems.
I swapped the trans, drive shaft, flywheel, pressure plate and rear end at the same time. At a driveshaft rotational speed of 5035 RPM - 95 MPH, we had heavy driveline vibrations.
I pulled the driveshaft out and had it rebalanced. It was out of balance. The vibrations remained - Now kicking in at 5300 RPM – 100 MPH.
I replaced the upper rear control arm with an adjustable one (Heim Joint chassis, stock rubber in differential) and new lower control arms (Stock length with poly bushings) to improve pinion angle.
Now the pinion angle is within 1.5 Degrees – No more adjustment in the upper control arm- not much change.
I was given an aftermarket engine cradle to drop the engine 0.5” and I shimmed the transmission up .1875” - Now the pinion angle within 1.0 degree. I spun the drive shaft myself on a friends machine using dial indicators to check for run out. No run out at 3500 RPM. Vibration now kicks in at 5560 RPM – 105 MPH.
Purchased a helm-jointed rear adjustable lower control arms. I was able to adjust the pinion angle to 0.0 degrees but the lower control arms were short and the bump stops didn’t line up. Pinion angle now 0.0 degrees at ride height (Rear pinion parallel with trans). The vibrations are now at 5830 RPM – 110 MPH.
Purchased a modified part to lengthen the upper control arm and I re-adjusted the lowers to stock length – Stile 0.0 Degrees pinion angle at ride height – Pinion is parallel / in line with trans at ride height.
I called a very good friend of mine to ask for his opinion. He wanted the car because he was having similar problems with a customer’s / project 2006 V6 Mustang. He swapped parts between the 2 cars – no luck. He checked the rear end pinion, ring gears and axles for run out and back Lash on my car with dial indictors– They looked great.
Both cars had drive shafts from the same manufacturer. He pulled both drive shafts and went to his go to Drive shaft shop.
My friend gets a call from a writer / friend looking for filler space for his series in car Magazine. I worked with the writer years ago when he wrote for magazines doing various articles for cars I worked on. He’s a good guy so I told my friend they could use the car for the needed filler space. The new drive shaft shop makes a 4” drive shaft – very nice unit. My friend puts the driveshaft in his car and tests it up to 140 MPH - 6500 RPM shaft speed (27” tire 3.73 gears) - No noticeable vibrations (Soft rear suspension bushings). They call it a day and the article went to print.
My problem 26.2” tire 4.1 gears. I stile see heavy vibrations with the 4” driveshaft at 115 MPH 6049 RPM shaft speed (Solid bushing rear connections - Heim joints ) which are not masking the problems but possibly enhancing them.
I pulled the trans, flywheel and pressure plate and replaced them with loaners just to make sure they were not contributing to the problem - No change in harmonic vibrations.
I purchased a driveshaft 3.5” OD using a CV Joint instead of the common commercial slip joint - Very nice driveshaft but no change. I installed hub centric rings for my lug centric wheels – no change.
I tested at Auto Club / Fontana Speedway a few weeks ago and ran the car up to 125 MPH to see if the harmonic vibrations would cancel out – 6575 rotational shaft speed. The vibrations got aggressively worse.
The car has been sitting since Auto Club – I am at a loss as to how to correct the problem. This has to be basic – What am I missing?
I’m open to all suggestions – Any & all advice would be appreciated.