135 MPH driveshaft failure

haven't read all the posts but thought I'd point out that those of you calling the poster a dumb-ass should be a little less harsh. So maybe the filming part while driving 130ish wasn't so bright but all he was doing by removing the speedlimiter was experimenting. Who amongst us hasn't done that? Unfortunately he found the limitation of his car. It happens. That's how you find the weak links. I can guarantee now that everybody in 'Stangland knows about this weak driveshaft and will upgrade before doing Bonzai runs without the speed-limiter

well..on second thought the fact that he kept pushing it after it was making the death rattle was pretty dumb

I have no problem with the owner, I would push the limits also and may not have considered the driveshaft. However I do have a problem with blaming Ford for the owner's misuse of the equipment.

The car was built to a price point with fail safe in place, the owner removed the fail safe and drove way past that point. Somehow some people think that is Ford's fault. I have no idea how Ford is to blame.

There is no way Ford should honor the warranty on a forced failure.

MY biggest problem with the owner (initially) is that if I heard a noise like the one in the video, (and probably a considerable vibration with it) I'd be slowing down to see what was going on (at 70 mph...much less 130). My first guess would have been a tire. Do you really want a tire to blow at 130, either? Slow down and figure out what the issue is. Don't continue to speed up.

It is the owners fault, of course it's the owners fault. They of course shouldn't get warranty coverage of the repair. Heck, it wouldn't surprise me if they end up with a hefty ticket after their local law enforcement sees the vid. That doesn't stop the fact that it surprises me that the driveshaft failed that close to the speed limiter. Yes it may have been lots more force for only 23mph more, but the sport upgrade comes with something like a 3.31 rear with no claims of an upgraded driveshaft. 3.31 rear at 112 mph has to be about the same driveshaft speed as 2.75 at 135.

45% more load may be a reasonable estimate of the increased one/rev imbalance due to speed, but what likely caused the failure was a dynamic response of the shaft.

If the increased speed ran the shaft into a bending mode, the actual stress seen by it and its joints could have been an order of magnitude higher. The V8 car having a two piece driveshaft arrangement, with the shorter halves having much higher fundamental frequencies of vibration (and corresponding critical speed), would allow a much higher safe shaft speed.

10% overspeed would be a sensible design margin to a shaft mode with the electronic speed limiter in place. This one appears closer to 20%.

I would guess that Ford knows exactly where the bounce, pitch, and bending modes of this shaft are and were comfortable with the existing speed limiter. The design brief for the car would have included designing around the intended max allowable speed.

Lame. It's a Mustang, even if it's a V6 Auto does Ford not realize people will tinker and modify their cars? The car has 300BHP for chrissakes, it's not like it's a average grocery getter. I mean if it's a little girly car that doesn't need to be tinkered with why does Ford sell performance parts for it?

The irony of a performance enthusiast slamming the guy for taking the speed limiter off did not escape me either. Though driving with one hand while holding the camera was stupid enough that I wouldn't have felt too bad if the drive shaft went up his ass for his stupidity.

p.s. I have two Fords in the garage right now and have owned thee Mustangs...

What's lame is being a cheap-ass and buying a bottom-of-the-barrel model, forcing it to do something it wasn't designed to do (but the performance models ARE), then whining about it when it breaks.

This car uses its 300hp to quickly accelerate to speeds well beyond what the average driver is going to see. If you feel the need to tinker with it and make it go beyond what Ford limited it to, add a performance drive shaft assembly to the tinkering list.

If I had a 305 hp automatic mustang the only thing I would want to do with it is tow my jet ski

deveous9 wrote: If I had a 305 hp automatic mustang the only thing I would want to do with it is unload my groceries

FTFY

aussiesmg wrote:

deveous9 wrote: If I had a 305 hp automatic mustang the only thing I would want to do with it is buy feminine hygiene products

FTFY

FTFY

In reply to MattW:

Very few people seem to think of the car as a whole when they make upgrades (like removing a speed limiter).

More power from the engine needs:

Better transmission Bigger brakes More cooling Better driveshaft.

Oh, look, I've got all that, now I have no traction. Time for:

Better tires Better wheels.

Oh, look, all that traction is breaking things because there is no slip in the system anymore. Time for:

Stronger trans, Stronger driveshaft. Stronger axles

Oh, car is getting heavy, time for:

More power..

See, it just goes in circles. If you upgrade one thing, the next thing to fail will be the next weakest part and so-on.

I his case it was the driveshaft, which took his whole car out with it.

Now he gets to do all those upgrades at once by buying a GT which would probably be cheaper than making a V6 economustang hotter anyway.

Shawn

Trans_Maro wrote: In reply to MattW: Very few people seem to think of the car as a whole when they make upgrades (like removing a speed limiter). More power from the engine needs: Better transmission Bigger brakes More cooling Better driveshaft. Oh, look, I've got all that, now I have no traction. Time for: Better tires Better wheels. Oh, look, all that traction is breaking things because there is no slip in the system anymore. Time for: Stronger trans, Stronger driveshaft. Stronger axles Oh, car is getting heavy, time for: More power.. See, it just goes in circles. If you upgrade one thing, the next thing to fail will be the next weakest part and so-on. I his case it was the driveshaft, which took his whole car out with it. Now he gets to do all those upgrades at once by buying a GT which would probably be cheaper than making a V6 economustang hotter anyway. Shawn

Yeah, that's pretty much my point.

112 MPH is well below anyone's expectations of the top speed of any modern sporty car or passenger sedan; a 90 hp CRX will get there. It's inadequate to the point where nobody would have suspected an engineering design point would have been set there - it reminds me of the 108 MPH limiters to protect tires on old GM cars.

I have no want to go that fast. The only way I would hit that speed would be on a race track. Even then, I would buy something totally different than a base model Mustang to race with.

Personally, I think they're great cars and that driveshaft failure wouldn't deter me from buying one.

chaparral wrote: 112 MPH is well below anyone's expectations of the top speed of any modern sporty car or passenger sedan; a 90 hp CRX will get there. It's inadequate to the point where nobody would have suspected an engineering design point would have been set there - it reminds me of the 108 MPH limiters to protect tires on old GM cars.

Anyone's expectations? That's a pretty broad statement. I'm willing to bet that most who buy a V6 automatic Mustang have no idea what the top speed of their car is, or ever will. Frankly, they are the type that SHOULD be limited to 112.

In reply to carzan:

If I bought a car that has done a high 13 1/4 at 100 mph, I wouldn't expect the speed limiter to be a mere 12 mph higher. I bet it does zero to the limiter in like 20 seconds or less.

AngryCorvair wrote:

aussiesmg wrote:

deveous9 wrote: If I had a 305 hp automatic mustang the only thing I would want to do with it is buy feminine hygiene products

FTFY

FTFY

Really? 305 hp and we make fun? This from the people who lust after yugos?

Im going to go drive my 88 hp escort.

Joey

it's not the HP.. it's the soul sucking autotrans it is backed up to

chaparral wrote: 112 MPH is well above the top speed almost any buyer of any modern sporty car or passenger sedan will take their car

FTFY.

Seriously, how many people buy a V6 Mustang, especially an automatic, and hit triple digits with it? I'd wager it's less than 0.5%. Of those <0.5% of owners who do it, I'd bet that 99.99% of the time they're driving, they're still under 85mph.

112 is at least 30-over the fastest speed limit in the country. Kinda hard to justify needing more mph out of the grocery getter, even if it is a 300hp grocery getter. Double-especially when the touted sporty attribute is acceleration, not top speed.

+1

joey48442 wrote: Really? 305 hp and we make fun? This from the people who lust after yugos? Im going to go drive my 88 hp escort.

mad_machine wrote: it's not the HP.. it's the soul sucking autotrans it is backed up to

Yeah..not my preference but a lot of folks like them. If you're not tracking a car then an auto makes much more sense.

That being said..I have tracked an auto, 700R4 behind a 6.0 LS2, and it was actually kind of cool. The car had enough torque that not having the perfect gear coming out of Oak Tree at VIR was still fun. Also, test drive a BMW 3 series with their auto. If that won't change your mind it will at least make you think. I was impressed that it did little things like hanging on to a gear in performance mode even if you were off the throttle. That helped with engine braking into a turn and stabilizing the car, as if it was a manual, while you completed the corner.

Auto transmissions are coming along. Not all of them are the dumb slushboxes of years past.

You can't have it both ways. It's either a performance vehicle or it's not. So with that in mind...

The car has a speed limiter, so have many cars over the years. I take a speed limiter as a gentlemans agreement, a way to keep the government content about OEM's making cars that are way faster than any sort of speed limit you could find on this side of the pond. Not as a way to curb design limitations on a vehicle. If the car isn't designed to go faster than 112MPH than don't give it a 300BHP engine. I mean it's a grocery getter after all?

What's next? Brake rotors that explode off when you hit 140mph? It's a slippery slope we're going down.

In reply to MattW:

What about rev limiters? It's a performance vehicle, so you should just be able to remove a 7800rpm rev limiter and expect the engine be fine at 9400 rpm?

There's just going to be concessions made for a $25k 300hp RWD 6-speed car that gets 30mpg, assuming that this really is more than a one-time incident.

MattW wrote: You can't have it both ways. It's either a performance vehicle or it's not. So with that in mind...

That's what we're trying to explain.

This is NOT intended to be the performance mustang.

Ford MAKES a high-perfomance mustang and a economustang.

This is not a GT balls-out high-performance car. This is a grocery getter, estrogen machine.

The new Honda Odyssey and Kia Sedona get 244hp, they should be able to go 135mph if anyone is stupid enough to try.

By your logic, they're a "high performance vehicle".

I wonder what, clearly faulty and under-engineered part on them would fail if pushed to those speeds. After all they're capable of doing it, so why shouldn't they be able to do it.