373's for 2012 V6
2nd Gear Member
Joined: Dec 2011
Posts: 151
From: California
I wrote a definitive piece on driveshaft failures, both OEM and aftermarket (v6mustangperformance.com search for a ds article written by westcoastsc). I was asked to consult with Shaftmasters on one of their returned driveshafts that broke during dyno testing. Failure was due to the dyno shop letting their foot off of the throttle too quickly. Caution your dyno tuner not to pull his foot too quickly from the throttle pedal once a run is completed. This can cause problems, but the probability of failure is so low, it is not something to be concerned about. I'm building a 700+ HP V6 with a Shaftmaster DS, and do not expect any problems. If you get the BMR front safety loop it is a direct bolt-on, and provides additional peace of mind.
The OEM stock DS are a two piece slider, where a formed tube with what looks like gear teeth, slides over another tube with the matching profile. The harmonic wave set up when a combination of factors is present is what is responsible for the steel DS failures. These factors are:
1. Lowered car with pinion angle not re-aligned for the required angle.
2. Removal of the speed limiter from the PCM.
3. Going over 120+ MPH. This can set up harmonic waves which can tear the driveshaft apart at the section of the ds where the sliding interface mates.
Unless you have all three of these factors present, the factory ds will not fail catastrophically. You will, however, strain the joints, eventually requiring replacement of the yokes. Most OEM driveshafts will experience the harmonics which makes the vibration level increase at MPH greater than 120. Again, however, the possibility of failure is very remote. If you are spinning your driveshaft at 7500 RPM or higher, then get an aluminum driveshaft. There are formulas to determine DS speed based on diameter and engine RPM.
I do not think most people will have problems no matter which driveshaft they run. Running the SC tips the scale towards an aluminum or carbon fiber DS.
I personally like the aluminum driveshaft, as it has lower rotating mass, but higher NVH is a problem.
Last edited by freyes; Jan 3, 2013 at 02:54 PM.
Joined: Dec 2012
Posts: 13
From: arkansas
I have the stock DS in my '11 and I, too, he been well over 120mph on quite a few occasions. Usually push it to 140-150. Never felt anything vibrate or weird..didnt know the DS sucked till I started reading it on this forum. Now saying that, I do think I'll fab up a DS loop soon!
Joined: Feb 2013
Posts: 5
From: Florida
I drove nearly 30,000 spirited miles with 3.73 gears and stock driveshaft. You guys need to stop creating hysteria. We also have members with gears who run their cars well into the triple digits as well as on the drag strip while still using the DS. Does a lighter, stronger DS help to improve performance and reliability? Yes. Is it absolutely needed? No. I would say that as long as you stay under 100mph for the most part, you will be fine without a doubt. Any time you test the limits of any car, you risk breaking things. People telling you what to do and don't even have the car.....that's all Ill say.
3rd Gear Member
Joined: Jul 2010
Posts: 720
From: VA
There is no need to change the differential cover. However, I will at some point do so only for cosmetic purposes. I'm more focused on the performance aspect first.
Man, I'm envious of you. I remember when I first got the gears how fast everything seemed. My car still seems fast, but I'm more used to it now.
Man, I'm envious of you. I remember when I first got the gears how fast everything seemed. My car still seems fast, but I'm more used to it now.
2nd Gear Member
Joined: Feb 2013
Posts: 223
From: Harrisburg, PA
you can get the V6 stock with 3.13 gears and it still has the 2 piece drive shaft. As far what i found the stock drive shaft is fine up until about 125mph. I know mine was fine at that speed, i didn't push it any further i didn't want to push my luck haha
