Drive shafts

[burt ragio]

What are the better balanced drive shafts offered for the 2004 Marauder price & part #s example ?
CV/PI+Taxie 3w7z-4602-ea $248.00
GM with sport package 3w724602-da $248.00
Mercury Marauder 3w32-4602-aa $365.00

[jfclancy]

WELL from what I have read DR has this
6061 Dynotech Driveshaft
Code: MM-MMDS
Price: $561.00
Amazing that the Marauder shaft is more expensive than those others as
that is a limiting factor on the MM.

[burt ragio]

I've heard there is another drive shaft avalable for less money than the dyno tech drive shaft. Does anyone know any thing about it ?

[sailsmen]

A perfectly balanced banana is still a banana.

[Fourth Horseman]

A perfectly balanced banana is still a banana.

That's what they say, but I've never been able to figure out how to mount up the u-joints to the banana. And yes, I have tried putting the banana in both ways, still no joy. Strangely, the shop manual is silent on proper orientation of the banana.

[sailsmen]

Peel it first then the laws of physics will no longer apply.;)

[KillJoy]

Mmmmmmm....... nanners......

:D

KillJoy

[Dennis Reinhart]

What are the better balanced drive shafts offered for the 2004 Marauder price & part #s example ?
CV/PI+Taxie 3w7z-4602-ea $248.00
GM with sport package 3w724602-da $248.00
Mercury Marauder 3w32-4602-aa $365.00


Drive line Critical speed
What it is –
Every rotating object has a “critical” speed or resonant speed, which is a function of its design, mass and stiffness. This is when the driveshaft is whipping in the middle, rather than spinning on a true centerline. For a driveshaft, this is also called “first bending mode”, indicating the shaft actually bows out into a boomerang shape (on a micro-scale). This first mode bending speed is usually referred to in a driveshaft frequency.

What it does –
The energy stored and released through the deflection of the driveshaft through the resonance creates lateral and vertical accelerations of >10g at the problem frequency, which results in broken transmission extension housings, cases and causes moderate to severe vibration at highway speeds (> 70 mph), particularly with axle ratios numerically higher than 3.27:1. This energy release, when compounded by excessive driveshaft imbalance (some is good, too much or too little is not), companion flange run out/imbalance and excessive driveline angles provides the driver with excessive vibration and boom and tortures the driver and driveline components in general.

Because of this, most vehicles have a speed limiter to prevent from entering this mode and causing damage to the driveline.

Some detail –
As mentioned above, the driveshaft rotates at a certain speed based on rear axle ratio; tire size and road speed, but is independent of engine speed (unless you have a vehicle such as a Porsche 944 or C5 Corvette which utilize torque tubes and transaxles, in which case the driveshaft turns at engine speed).

The factors governing driveshaft critical speed include its material properties (i.e., Bulk Modulus of Elasticity which is roughly analogous to material stiffness), diameter, and length and to a lesser degree, wall thickness.

The only factor you can really modify to affect critical speed is material choice. Length is package-dictated, and diameter is usually constrained by driveline tunnel space as well. The answer then becomes a bit simpler – replace your steel shaft with an aluminum or MMC (metal matrix composite) shaft. Both offer reduced weight, which is key in this frequency range. MMC offers the additional bonus of additional damping and stiffness over a typical aluminum alloy.

As mentioned above, at the frequencies in question, a change in rotational mass has a greater impact on resonant frequency than a change in stiffness does, partly since it is easier to reduce mass than increase stiffness (adding stiffness almost invariably means adding mass -- a vicious circle), but particularly since resonant frequency is equal to the sqrt (k/m), where m is mass and k is stiffness. Here m is a stronger function being the in the denominator of a square root. So you can see that as “m” gets smaller, the resonant frequency “f” gets much bigger.

The use of an aluminum shaft provides a dual purpose – increasing critical speed out of the operating range AND directly reduces the rotational forces since those rotational forces are governed by:

F = mr w**2
Where w is rotation speed, m is the mass and r is the radius at which it is spinning.

This means that a 50% reduction in rotational mass results in 50% less rotational force. So, when a driveshaft rotates out of true, due to run out of the shaft itself or due to trans output shaft or axle companion flange run out, the reduced mass * the radius of gyration (i.e., run out) product is smaller than for the same conditions with a steel shaft.

This becomes important not only at critical speed, but at more normal operational speeds where the effects of run out and mass imbalance are more evident than those of resonance:

For a typical Fox or SN95 Mustang, driveline critical speed is around 95-100 Hz. Using stock tires we have the following:

225-60R15, 225-55R16, 245-45R17 all rotate at 812-820 revs/mile at 60 mph.

This give is 13.5 Hz wheel frequency at 60 mph, and assuming a 3.27 axle, we then have:

812/60*3.27 or 44.25 Hz , driveline frequency.

So, 100/44.25*60 yields a driveline critical VEHICLE speed of 135 mph. A good rule of thumb states that the objectionable driveline forces will start becoming significant at 70% of resonant frequency, so for the case of the 3.27 axle, the boom and vibration may be felt beginning at 95 mph.

Typically, 3.27 axles don’t provide the driver with much to complain about; it is 3.73 and above which create the concerns. Using a 3.73, we find that

13.53*3.73 gives 50.5 Hz wheel frequency at 60 mph (substantially higher than the 3.27)

And the critical VEHICLE speed then becomes

100/50.5*60 or 119 mph.

Taking 70% of 119 mph equals 83 mph, certainly a speed at which some Mustang drivers experience occasionally.

For a 4.10 axle, the “70% speed” is 76 mph!

Compounding this problem are factors like transmission output shaft run out, imbalances and run outs from components such as the reverse sun gear, driveshaft, companion flange and pinion pitch line run out (a torque induced run out created when the pinion tries to crawl up the face of the ring gear involutes).

Combine these factors and the already marginal NVH resulting from proximity to 1st bending (critical speed) and the NVH becomes absolutely agricultural.

The aluminum shaft minimizes the contribution from companion flange run out and the driveshaft’s own run out, directly due the lower mass. The pinion is free to pitch +/- 20 degrees and adding in any run outs of the companion flange or driveshaft at the pinion end results in the driveshaft mass having a large eccentric path to wobble about. It is this path times the mass of the driveshaft, which gives the characteristic boom and vibration at highway speeds.

Thus, as Newton predicted, as mass decreases so will the forces. That is why an aluminum shaft is your friend when coupled to 3.73s.

One side note: that great big mass on your pinion nose, fondly named by driveline engineers after the appendage on a male moose, is tuned to 45 Hz, the frequency at which the 2nd order forces created by u-joints as they rotate, force the pinion to bounce or pitch up and down and shake you by the seat of your pants and create an uncomfortable boom in the car. Once again run outs and imbalances will modulate this 2nd order driveline phenomenon to make it worse, so the moral is, LEAVE THE MOOSEB-, uh, DAMPER ON the pinion nose!

Another item: you CAN expect more axle noise when using an aluminum shaft however, which does not necessarily mean the pinion depth or side shims are incorrect, or that the gear cutting process is flawed. It just means that the aluminum shaft is more willing to “bend” circumferentially, torsionally and in a double hump (2nd bending) much more easily than a steel shaft.

Recall my prior statements at the very beginning about aluminum stiffness vs. steel? Picture a piece of sheet metal ducting. Bend it and it makes a WA-WA sound. That is pretty much what a driveshaft does, but at a much higher frequency – higher than even the dreaded “critical speed” of 100 Hz.

Axle noise will occur from about 350 Hz all the way through 500 Hz, sometimes even higher than that. The energy comes from the teeth meshing at the pinion/ring gear interface. This energy is transmitted to the driveshaft (and suspension components) and makes them deflect in the same sense as a piece of sheet metal goes WA-WA. Aluminum is less stiff than steel and takes less energy to deflect it, so it is far more inclined to make your axle go WOOOOO as you drive down the road at 45-70 mph.

Assuming again a 3.73 axle ratio, which has 11 teeth on the pinion and 41 on the ring gear, the axle noise frequency is calculated as (at 45-70 mph):

815/60*3.73*11 or 557 Hz at 60 mph.

This means the WOOO you hear at 45 mph is about 418 Hz and the WEEEEEE you hear at 70 mph is way up there at 650 Hz. You can’t SEE the driveshaft is bending and breathing and twisting, but it is telling you that precisely that is occurring.

So, now armed with this information, you now understand the basics of your vehicle’s driveline.

Information provided by JW

[TAKEDOWN]

WOW! Holy SHHH...DENNIS you lost me by the 2nd paragraph. Thanks for info, by the way it almost took me an hour to put on the pro Gard. That is why I am NOT a mechanic.

[Svashtar]

Bottom line is that the MMX driveshaft is cheap insurance. I got mine from Dennis in 2004, because he took the time then to educate everyone on this issue, and I knew that I would (occasionally) need to get up to 120-130 or so in order to pass someone. :rolleyes:

OR, much more likely, want to drive at 80-90 for long distances on the interstate.

After putting money into the rear end and the tranny, I'm happier than ever I decided to get this as well. I do believe the stock DS we have is a balanced one that's a cut above the regular one offered in the panther platform, but with 4:10's and other mods I felt the metal matrix composite shaft was the way to go.

Norm

[Stranger in the Black Sedan]

You can still find MMX shafts (identifiable by the color striping) in junkyard ex CVPI cars. If I can positively ID one, they can be had for around $75-100 each

[Dennis Reinhart]

You can still find MMX shafts (identifiable by the color striping) in junkyard ex CVPI cars. If I can positively ID one, they can be had for around $75-100 each


Even these drive shafts were rated to 128 MPH, the only safe option is a Dynotech DS

[KillJoy]

Even these drive shafts were rated to 128 MPH, the only safe option is a Dynotech DS


Uhhh...... if it is rated at 128mph continuous..... why would anyone need to buy a Dynotech?

I average about 85-90 at MOST. Occasionally triples are seen, but not sustained.

I do not see ANYONE on this forum driving 128mph for more than a minute or two AT MOST!

:dunno:

KillJoy

[Dennis Reinhart]

Uhhh...... if it is rated at 128mph continuous..... why would anyone need to buy a Dynotech?

I average about 85-90 at MOST. Occasionally triples are seen, but not sustained.

I do not see ANYONE on this forum driving 128mph for more than a minute or two AT MOST!

:dunno:

KillJoy


Well you should know by now. Even Steve Babcock verified what has been posted, and what you fail to account for is if any member has installedc 4:10 you will reach critical driveline vibration well before 100 MPH, installing the drive shaft is members choice, I respect you opinion, and I have mine.

[KillJoy]

Well you should know by now. Even Steve Babcock verified what has been posted, and what you fail to account for is if any member has installedc 4:10 you will reach critical driveline vibration well before 100 MPH, installing the drive shaft is members choice, I respect you opinion, and I have mine.


I had not taken 4.10's into account.....

:help:

KillJoy

[magindat]

it almost took me an hour to put on the pro Gard.
:eek:

That is why I am NOT a mechanic.

Good thing!;)

The summary of the JW monologue is: the flex is inherent to the material, not the balance.

Just call Dennis, ask him for the 'right' drive shaft. Tell him your CC number. Be happy and more importantly, safe.

[magindat]

I do not see ANYONE on this forum driving 128mph for more than a minute or two AT MOST!

:dunno:

KillJoy

Haven't seen me then, have ya?

130+ sustained with 4.10's about 3-4 times a year....

[Stranger in the Black Sedan]

The stock D/s is good to around 130. The MMX shaft HAS to be better than that because it's lighter and stiffer at the same time. Whether the factory "rated" it for higher, I don't know. But the MMX junkyard CVPI shaft is going to afford an improvement over stock. It is, after all, an MMX driveshaft.

[Dennis Reinhart]

The stock D/s is good to around 130. The MMX shaft HAS to be better than that because it's lighter and stiffer at the same time. Whether the factory "rated" it for higher, I don't know. But the MMX junkyard CVPI shaft is going to afford an improvement over stock. It is, after all, an MMX driveshaft.


Ok, lets do the math, stock shaft 128 MPH. MMX 130 MPH - 128 MPH = 2 MPH gain. And still will not be safe if you have 410's and exceed 100MPH, but I understand cost is cost, all I am trying to explain is reason behind the Dynotech drive shaft. And I believe I have done that.

[Stranger in the Black Sedan]

I would have to do the math w/ the MMX shaft. I have a driveline critical speed calculator on the PC somewhere. I have a hard time believing MMX only afforded 2 mph over aluminum. Ford would not have made the shaft if that were the case, it just wouldn't be cost effective. You'll get more than 2 mph critical speed variance due to imperfect balancing. I'm not arguing, just trying to acknowledge that the stock MMX shaft on the CV's is probably not as worthelss as people think.

[red]

I would have to do the math w/ the MMX shaft. I have a driveline critical speed calculator on the PC somewhere. I have a hard time believing MMX only afforded 2 mph over aluminum. Ford would not have made the shaft if that were the case, it just wouldn't be cost effective. You'll get more than 2 mph critical speed variance due to imperfect balancing. I'm not arguing, just trying to acknowledge that the stock MMX shaft on the CV's is probably not as worthelss as people think.

Talk to Darrin about the construction of the Police MMX driveshaft (he's worked with these).

Personally, I'm not wild about the quality on the Dynotech after seeing several (new and under the car). I'm planning to have a custom 4" 6061 T6 aluminum shaft made by Dennys Driveshafts (they can balance up to 10,000 RPM--my request is 6500). Dennys is extremely well known in the racing community.

If anyone is in the Kenmore, NY area and interested in visiting their shop to get drive shaft measurements taken, let me know. If so, I'll order a drive shaft from them and report back to the site with pictures and such. There's about a three to four week lead time for their products.

Also, concerning cost... $500-$600 is expected for a 4" 6061 drive shaft. I called many places in my search.

[Stranger in the Black Sedan]

Red, a 4" aluminum shaft is going to be heavier than the stock 3.5" shaft, and not have that much higher of a critical speed. I don't think you are going to gain anything at all over stock, other than strength (but you are not going to break the stock shaft anyway)

[red]

Red, a 4" aluminum shaft is going to be heavier than the stock 3.5" shaft, and not have that much higher of a critical speed. I don't think you are going to gain anything at all over stock, other than strength (but you are not going to break the stock shaft anyway)

You're right about the weight; a 4" is 1 to 2 pounds heavier than stock (didn't you make a steel--not chromo--shaft?... that's on the order of 5 to 10 pounds heavier). However, this 4" 6061 is not a significant increase in weight, and while the little bit of weight could contribute to the whipping, the diameter and wall construction will increase the critical speed. If you don't believe me, call any reputable drive shaft shop, describe to them the problem we have on our cars, and ask them how to solve it (their answers will be material, decrease weight, and increase diameter). Even Dynotech claims their 4" 6061 to have a higher critical speed than their former 3.5" MMX.

[Stranger in the Black Sedan]

You're right, our stock DS has around a 6000 rpm critical speed, which translates to around 140 mph w/ 3.55 gears. So your 4" 6061 would afford you another 30 mph, assuming 3.55 gears.

Yeah I still have a 3.5" mild custom shaft for this car, sitting in the garage, balanced and w/ new yoke and u joints. That had actually a few hundred rpms higher critical speed than the stock aluminum shaft, because although the steel is a lot heavier, it is also a whole lot stiffer than the aluminum. Higher critical speed was not why I built it though. Why, do you want it? I am not going to ever use it again. I was trying to isolate driveline noise at the time I had that brilliant idea. Surprise, steel transmits noise better than aluminum. So that was the complete opposite of what I wanted to do. But that steel shaft I have is the friekin strongest thing ever, save for moly. 3.5" even in mild steel, is JACKED.

[Dennis Reinhart]

Talk to Darrin about the construction of the Police MMX driveshaft (he's worked with these).

Personally, I'm not wild about the quality on the Dynotech after seeing several (new and under the car). I'm planning to have a custom 4" 6061 T6 aluminum shaft made by Denny's Drive shafts (they can balance up to 10,000 RPM--my request is 6500). Denny's is extremely well known in the racing community.


Denny's is not a vendor here, no vendors here sell Denny's. As fas as I know there is no one that spins a shaft to 10K, but I could be wrong. There are hundreds of happy Dynotech drive shaft owners here, as as far as I know, NO one has had a issue with Dynotech they make drive shafts for the Marauder T bird CV Chevy SSR they sell a Superior drive shaft, Denny's bought one of Dynotech older balancing machines years ago, Ford buys a lot of there drive shafts from Dynotech. They use 6061 T6 aluminum they use superior Dana Spicer U joints they can spin balance them between 6,000/8,000 RPM. Every Florida FHP Marauder has them not one has ever failed, and they run these cars over 150 MPH. Denny's started there shafts after Dynotech, but you can buy from them if you like, but Dynotech is a proven product they are now doing retro kits for the newer Mustangs and Shelby's. If any one wants to get all the facts just call Dynotech ask for Jim Vilapondo 1-248-362-2777

[Stranger in the Black Sedan]

The "better" local shops can spin up to 3k rpms. A lot of local shops only spin to like 1500 rpms. so 6000+ is very good

[red]

Denny's is not a vendor here, no vendors here sell Denny's. As fas as I know there is no one that spins a shaft to 10K, but I could be wrong. There are hundreds of happy Dynotech drive shaft owners here, as as far as I know, NO one has had a issue with Dynotech they make drive shafts for the Marauder T bird CV Chevy SSR they sell a Superior drive shaft, Denny's bought one of Dynotech older balancing machines years ago, Ford buys a lot of there drive shafts from Dynotech. They use 6061 T6 aluminum they use superior Dana Spicer U joints they can spin balance them between 6,000/8,000 RPM. Every Florida FHP Marauder has them not one has ever failed, and they run these cars over 150 MPH. Denny's started there shafts after Dynotech, but you can buy from them if you like, but Dynotech is a proven product they are now doing retro kits for the newer Mustangs and Shelby's. If any one wants to get all the facts just call Dynotech ask for Jim Vilapondo 1-248-362-2777

Denny's Driveshaft is not a vendor here, nor is Dynotech. I understand that you carry their product and as a result many people have bought this driveshaft and of course have been quite happy with it (it is a decent product, and I did not imply that it would fail). However, it's not the only driveshaft on the market, and I am personally interested in trying something different. I have looked around and was most impressed by the craftsmanship and quality of Denny's. And, Denny's claim is a balance of up to 10k RPM (see http://www.dennysdriveshaft.com/). Anyway, I am throwing this out there for others to see. If anyone else is interested, there may be potential for a group buy.

[Stranger in the Black Sedan]

No takers on my steel driveshaft-of-doom huh? LOL It was a good idea at the time. If I am ever making over 1000 ft lb I can swap it back on I guess.

[Svashtar]

All I know is I have done several high-speed long distance runs with the car at 125-130, and the car just hums. Sounds like a turbine just cranking away and there's still pedal left, which is scary.

There is no vibration under me at all with the MMX. The only concern I have is that the front end lightens up and feels like it's floating. If we had a real spoiler in back like on many of the mustangs with some slight upward tilt to it that would probably be eliminated as well.

Norm

[Icarus]

I'm running a Denny's 4" shaft on my Linc and love it.
I taked to both Denny's and DynoTech when I was looking and they were both good in giving me the info I wanted. Prices were similar, and Denny's balanced up to a higher speed. I went with Denny's due to the balancing and a lil better info I got from them, and they are closer to me. In the searching around I did, I heard of a few more issues with the DynoTech (but that really doesn't mean alot anyways, as the Linc's are real tight with the 4" shaft from anyone.)
I don't think you can go wrong with either imho ;)

[UncleLar]

So what is the "critical speed" with a dynotech driveshaft with 4.10 gears?

[Stranger in the Black Sedan]

If you google you can look this up by length and material (and wall thickness)

[UncleLar]

Darn,I was hoping to get away without having to do any cyphering,the 6 years I spent in 5th grade didn't leave me well prepared for all that,lol

[Stranger in the Black Sedan]

Our D/s is around 55" if I remember correctly. That being the case:

A 3.5" (stock diameter) 6061 shaft would have a critical speed of around 7400 rpms. A 4" 6061 would be barely higher, around 30 rpms higher. Not worth mentioning from a crit speed standpoint, but the 4" shaft will obviously be stronger.

Factor in the gear ratios to find what the road speed will be at this critical speed.

Isn't the stock aluminum drivehsaft already 6000 series aluminum? If that is the case than a 6061 stock size shaft would offer no benefit

[larryo340]

:laugh: That's a good one

Darn,I was hoping to get away without having to do any cyphering,the 6 years I spent in 5th grade didn't leave me well prepared for all that,lol