Chromeshadow

Captain, thanks for posting the links! Great info!

JayyVee

Going to happily C/P this Capt'n and place in my sig, and join the 'inform the gang' sig party if you don't mind.

Good point 97tpls, I did not know (or missed the blog entry) where AM's own DS went up in flames at such a low roll, I'd have to think that's related to all the work 'under' the hood unfortunately. But, that is what it is too, so food for thought indeed.

Start testing the limits, and pushing them - be prepared to pay to play, that's the motto across all makes/models.

Mownt

I may be totally off here but, isn't the opposite true?

If you change the rear end gear ratios then the amount of turns it takes to move the wheels one rotation is increased but, the amount of rotations on the drive shaft is not (unless you change the gearing in the transmission).

So lets say the max speed in 1st gear is 30 MPH (with 2.73 gears @7000RPM), lets also hypothetically say that 1 rotation of the crank = 1 rotation of the drive shaft, rotation of the drive shaft would be 7000 RPM.

If you increase the gear ratio of the rear end to 3.73 it would take 1 extra turn of the drive shaft to move the wheel 1 full rotation. Since the transmission gears didn't change the drive shaft would still be spinning at the same 1 rotation of the crank to 1 rotation of the drive shaft (7000 RPM)

The drive shaft would be spinning at the same rate but, the wheels would actually be going slower. Max speed in 1st would reduce down to a hypothetical 25 MPH. This would force you to switch into 2nd since you would be at red line.

No actual math was used in this post.

CaptainRon

No, its the other way around. If you have a 2:73.1 then your driveshaft will rotate 2.73 times around to move the drive tires once. hence the 2:73.1. 1 meaning 1 rotation of the drives and 2.73 rotations for the driveshaft.
So if you put in 3.73's then the shaft will rotate 3.73 times to move the drive tires once. got it?

Mownt

That is what I was saying.

Lets pretend Engine Red Line is 1000 RPM:

1000/2.73 = 366.30 (tire rotation)

1000/3.73 = 268.09 (tire rotation)

The tires will be rotating slower at the same RPM and you'll reach Engine Red line earlier.

mustangtwo

I see folks referencing "at twice the speed limit" when discussing drive shaft issues at high speed. I picked up a new 2012 base model v6 with 6 speed and 2.73 gearing last month and am fortunate to be a military guy stationed in the Stuttgart, Germany area.

Some of the best quality public highways known as the Autobahn exist here and you WILL get passed often even at governor limited speeds of 118mph.
90-100mph highway speeds are routine and occasionally higher when passing etc...

Are there any real world issues with the stock drive shaft when driving highways at the higher speeds that are routine here in Europe?

eastexsteve

I know that SCT speed-limits their 2012 v6 tunes to 125mph. I found this out personally, and then called them to verify it. It's because of the drive shaft issue. However, I've only had the car that fast one time, and I don't consistently drive over 90mph at any time. But, I have experienced a very slight high frequency vibration in the shifter while decelerating at much lower speeds (50mph to 30mph). One time when it did it, I pushed in the clutch, and it went away. This tells me that it's engine-oriented. Has anyone else with a stick felt this? I have no other mods other than an SCT 93 octane performance tune.

Funster_2011V6

Dual mass flywheel causes the vibes. Ford says they designed it that way.

https://mustangforums.com/mustang-ts...Model-Mustang/