driveshaft make my car not safe to drive highway speeds? - Page 2 - MustangForums.com

Go Back  MustangForums.com > Ford Mustang Tech > 2005-2014 Mustangs > V6 S197 General Discussion > 3.7L V6 Technical Discussions
Reload this Page >

driveshaft make my car not safe to drive highway speeds?

Notices
3.7L V6 Technical Discussions Any questions about the new engine, transmission, exhaust, tuners/CAI, or gearing can be asked here!

driveshaft make my car not safe to drive highway speeds?

Old 05-06-2012, 05:13 PM
  #11  
Chromeshadow
3rd Gear Member
 
Join Date: Apr 2011
Location: Wisconsin
Posts: 918
Default

Captain, thanks for posting the links! Great info!
Chromeshadow is offline  
Old 05-07-2012, 02:51 PM
  #12  
JayyVee
2nd Gear Member
 
JayyVee's Avatar
 
Join Date: Oct 2011
Location: Woodstock, GA
Posts: 485
Default

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.
JayyVee is offline  
Old 05-09-2012, 11:25 AM
  #13  
Mownt
 
Join Date: Apr 2012
Location: Missouri
Posts: 12
Default

Originally Posted by Old Mustanger View Post
Not to point out the obvious, but if someone has a higher ratio gear installed this speed limit will need to be lowered significantly.
The "speed limit" is really the RPM limit of the drive shaft, in other words it is the rotational speed when the natural frequency of the tubing is reached = splooey!

What rear gear is standard on a 6er?
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.
Mownt is offline  
Old 05-09-2012, 03:18 PM
  #14  
CaptainRon
2nd Gear Member
 
Join Date: Mar 2012
Location: Texas
Posts: 228
Default

Originally Posted by Mownt View Post
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.

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?
CaptainRon is offline  
Old 05-09-2012, 03:52 PM
  #15  
Mownt
 
Join Date: Apr 2012
Location: Missouri
Posts: 12
Default

Originally Posted by CaptainRon View Post
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?
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.
Mownt is offline  
Old 05-13-2012, 02:23 AM
  #16  
mustangtwo
 
Join Date: May 2012
Location: Germany
Posts: 1
Default

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?
mustangtwo is offline  
Old 05-13-2012, 08:18 AM
  #17  
eastexsteve
 
Join Date: Nov 2011
Location: TX
Posts: 27
Default

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.
eastexsteve is offline  
Old 05-13-2012, 04:18 PM
  #18  
Funster_2011V6
2nd Gear Member
 
Funster_2011V6's Avatar
 
Join Date: May 2010
Location: Indiana
Posts: 293
Default

Originally Posted by eastexsteve View Post
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.
Dual mass flywheel causes the vibes. Ford says they designed it that way.

https://mustangforums.com/mustang-ts...Model-Mustang/
Funster_2011V6 is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
msavoia23
4.6L (1996-2004 Modular) Mustang
12
07-07-2018 12:08 PM
mweiland
2005-2014 Mustangs
0
08-16-2015 10:59 AM
92 5.0stang
5.0L (1979-1995) Mustang
4
08-13-2015 06:46 AM
Milan Dragway
Members Rides and Car Show Section
0
08-12-2015 03:43 PM
djbigskrilla
2005-2014 Mustangs
13
08-11-2015 12:59 PM


Thread Tools
Search this Thread
Quick Reply: driveshaft make my car not safe to drive highway speeds?


Advertising
Featured Sponsors
Vendor Directory

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.