Differential damper

[308 Cal. Bullitt]

O/P,

Running a problem veh on jack stands

(making sure you're rear wheels are at ride ht, especially on solid axle vehs),
*so, not at full extension of rear shocks*

is where we will often to start, in your situation.

Going a step beyond, & running the car on a chassis dyno for a few hrs, can help eliminate items as well, via a loaded drive train, vs free wheeling.

Automotive stethoscope use, while spinning it up, can help at times. Not always.

Safety is paramount. I rarely let my own employees crawl around these cars while it's up & spinning the tires. Just be careful.

A few hrs on stands, or spending $100-$150 an hr on an inertia wheel/chassis dyno is mucho cheaper than throwing parts at a car, as you already know.

Like I said, just be careful. No loose clothing.
Put car in neutral while not running & rotate components to check total indicated runout on driveline or at other locations.

Building custom race, offroad, & performance 4130 rearends for decades can require this type of diagnostic process on occasion.
We developed a reputation in a metro area of 7 million pple, as the go to shop for this type of analysis. Just gotta be thorough.

You'll find it. Just be methodical.

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[GTP]

.... It is fully optioned Kona blue with red recaros. Every option sold that year.

Please tell me it has silver wheels!

 

[Manchild]

Has Ford Performance heavy duty axels professionally installed, and they are tight. Shop that installed driveshaft loved it. ( check out Gulf Coast. They furnish driveshafts for Steve Morris). Guy I bought car from never dragged raced in his life.

 

[NGOT8R]

Has Ford Performance heavy duty axels professionally installed, and they are tight. Shop that installed driveshaft loved it. ( check out Gulf Coast. They furnish driveshafts for Steve Morris). Guy I bought car from never dragged raced in his life.

Sounds like you’ve got a solid ride, aside from the vibration issue. The previous owner definitely set out to address some of the weak links on the car, which was a bonus for you.

Stay with it and you’ll get to the bottom of it soon.

 

[Manchild]

O/P,

Running a problem veh on jack stands

(making sure you're rear wheels are at ride ht, especially on solid axle vehs),
*so, not at full extension of rear shocks*

is where we will often to start, in your situation.

Going a step beyond, & running the car on a chassis dyno for a few hrs, can help eliminate items as well, via a loaded drive train, vs free wheeling.

Automotive stethoscope use, while spinning it up, can help at times. Not always.

Safety is paramount. I rarely let my own employees crawl around these cars while it's up & spinning the tires. Just be careful.

A few hrs on stands, or spending $100-$150 an hr on an inertia wheel/chassis dyno is mucho cheaper than throwing parts at a car, as you already know.

Like I said, just be careful. No loose clothing.
Put car in neutral while not running & rotate components to check total indicated runout on driveline or at other locations.

Building custom race, offroad, & performance 4130 rearends for decades can require this type of diagnostic process on occasion.
We developed a reputation in a metro area of 7 million pple, as the go to shop for this type of analysis. Just gotta be thorough.

You'll find it. Just be methodical.

 

[Manchild]

Thanks, it is really a nice car. I’ sure my son and I will get to the bottom of the problem eventually.

 

[GregO]

QA1 supplies the CF DS for Fords GT500. Interestingly QA1 & Ford stayed with the rear CV joint for a reason.
Re-clocking and retesting is almost mandatory with that rear Spicer U-joint on an IRS car.

 

[Manchild]

Gulf Coast carbon fiber driveshaft needs no additional adapters. Comes with aluminum adapter flanges from Sonnax. Bolts directly into existing ORM flanges. Please note that vibration is exactly the same with stock, chromoly and current driveshaft.
By the way, car now has gloss black GT350 wheels with 305 rear Nitto drag radials and Nitto 285 fronts.

 

[GregO]

Please note that vibration is exactly the same with stock, chromoly and current driveshaft.

It’s a known fact the factory has installed the OEM DS incorrectly at the pinion yoke. Going from the CV to U-joint introduces new problems.

 

[Manchild]

Ok, so what to do about it now? Spent big money of the latest driveshaft.

 

[GregO]

Ok, so what to do about it now? Spent big money of the latest driveshaft.

Here’s a screen shot of a M6G member’s observation and corrective action with the OEM DS that vibrated.
I agree common logic suggests a balanced DS shouldn’t need to be re-clocked but that isn’t the case.
6 bolt yoke flange, the position you’re in now vibrates so 5 more locations to test.
Your car your choice, that IRS Diff moves all over the place, this isn’t a 4-Link or leaf spring situation hence it has a CV joint but there’s no going back on that with your CF DS.

 

[Manchild]

Ok, thanks.

 

[308 Cal. Bullitt]

Thanks, it is really a nice car. I’ sure my son and I will get to the bottom of the problem eventually.

 

[DrZed]

Is there a transmission mount insert in there? Some are black and not red, and can fool you looking stock. It will give you that vibration you're talking about.

 

[Manchild]

I don’t think so. When I installed shims in trans crossmember I think it looked stock, but I’ll take another look.

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