Driveshaft question

[svtmerc]

Is there a difference between the Marauder driveshaft and the Police one? They are both aluminum and come from 4r transmissions with long tailshaft so I was guessing they were the same ...

Also what markings identify a MMC driveshaft?

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[Mr. Man]

Police driveshafts are marked "Police" IIRC. There are color bands that differentiate the shafts from one another. Can't recall the color order for the one everyone wants. Do a quick Google search and I'd bet you'd find a quick answer to your query.

[gdmjoe]

How to identify the metal matrix aluminum drive shaft:

· Part number XW7Z-4602-AA
· Painted stripes pink and green and also blue (not always)
· The following printed or inscribed on the drive shaft “MMC Police ALCOA C291-T6”
· Shiny, smoother surface than the standard aluminum drive shaft
· Police interceptor with a build date of second half 1999 and all of 2000, rear axle ratio of DK or R2
.

[svtmerc]

Police driveshafts are marked "Police" IIRC. There are color bands that differentiate the shafts from one another. Can't recall the color order for the one everyone wants. Do a quick Google search and I'd bet you'd find a quick answer to your query.I've seen the standard police ones... My question about them is there a difference in them physically from the Marauder one. I noticed a slight wobble in my driveshaft with it in gear and the car in the air. I didn't know if I should try finding a shop to straighten and balance mine or should I just replace mine with a police one, and if I did that would the speed/rpm rating be different.


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[svtmerc]

How to identify the metal matrix aluminum drive shaft:

· Part number XW7Z-4602-AA
· Painted stripes pink and green and also blue (not always)
· The following printed or inscribed on the drive shaft “MMC Police ALCOA C291-T6”
· Shiny, smoother surface than the standard aluminum drive shaft
· Police interceptor with a build date of second half 1999 and all of 2000, rear axle ratio of DK or R2
.Great, thanks for the info on these.... I did spot some 2001 p71s and looked at the driveshafts and did not see any indications of them being the MMC.... Now I know why.... I was looking at the wrong year car.

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[BAD MERC]

Mickeys Driveline in Fort Myers has been around FOREVER. They've done work for me twice and I cannot recommend them highly enough. If you exhaust all options, take it there.

https://www.yellowpages.com/fort-myers-fl/mip/mickeys-driveline-powertrain-6885366

[PVEPANTHER]

I have read a few posts on line where people say that the driveshaft starts to be a problem at high speed….is that true or normal internet paranoia? If true is there a fix? Thanks

[crouse]

With my 4.10 gears, I took out my pinion bearing onetime when I was north of 120 mph. I'm guessing because it need to be balanced better. Or it it possible where the flange on the drive shaft meets the flange on the rear end housing isn't perfectly aligned?

[SilverPhoenix]

I have read a few posts on line where people say that the driveshaft starts to be a problem at high speed….is that true or normal internet paranoia? If true is there a fix? Thanks

Oh man, that was a hot topic/debate many years ago. IIRC, the 'problem' starts when you hit speeds of 115mph+...for hundreds of miles. But again, that was a long time ago, so I may not be remembering correctly...heck, you might be able to find that thread/discussion if you search for it.

[svtmerc]

I can't speak for the Marauder, since ive not had mine that fast, but my old 2002 Marquis was up to 144 mph with 3 people and tools in it. I had 3:73s in it and that car has a longer steel driveshaft. We did not experience anything but the feeling of riding amongst the clouds. That was about over the course of 3-5 miles over 100 mph... So not a very long time, but i have to assume the mm driveshaft is a better part than the marquis one

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[gdmjoe]

----------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.

[offroadkarter]

critical driveline speed isn't a myth, a few members on this forum have blown the tailshafts off the transmission from sustaining 140+ for miles and miles. The problem is the overall length of the one piece shaft, it really should have been a two piece from the factory.

The factory Marauder driveshaft is the "police" normal aluminum shaft. The Alcoa Metal Matrix Composite shafts were only used in some 99/00 model P71s.

[blazen71]

What is the "Metal Matrix Composite"? I always wondered

[svtmerc]

What is the "Metal Matrix Composite"? I always wonderedI never looked into that... I think it is just a stronger aluminum alloy

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[88LTDCV351]

What was that vendor everyone used to recommend on here? Dynomax or something like that? Aluminum or carbon fider driveshaft or something. Supposed to be an upgrade from the original driveshaft. But still I guess folks said the MMC was the better upgrade. So how much better was the MMC versus the Dyno something or other?

[svtmerc]

Here is what you are looking for:

https://www.dynotechengineering.com/drive-shaft/custom-replacement-drive-shaftshttps://uploads.tapatalk-cdn.com/20220607/142a28bf7e6433b101e0687f6f1299 b0.jpg

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https://uploads.tapatalk-cdn.com/20220607/0322d2d26b018a08a3cdd81c2cb80e 97.jpg

[gdmjoe]

blazen71 - What is the "Metal Matrix Composite"? I always wondered


Composition
MMCs are made by dispersing a reinforcing material into a metal matrix. The reinforcement surface can be coated to prevent a chemical reaction with the matrix. For example, carbon fibers are commonly used in aluminium matrix to synthesize composites showing low density and high strength. However, carbon reacts with aluminium to generate a brittle and water-soluble compound Al4C3 on the surface of the fiber. To prevent this reaction, the carbon fibers are coated with nickel or titanium boride.


Matrix
The matrix is the monolithic material into which the reinforcement is embedded, and is completely continuous. This means that there is a path through the matrix to any point in the material, unlike two materials sandwiched together. In structural applications, the matrix is usually a lighter metal such as aluminium, magnesium, or titanium, and provides a compliant support for the reinforcement. In high temperature applications, cobalt and cobalt-nickel alloy matrices are common.


Reinforcement
The reinforcement material is embedded into the matrix. The reinforcement does not always serve a purely structural task (reinforcing the compound), but is also used to change physical properties such as wear resistance, friction coefficient, or thermal conductivity. The reinforcement can be either continuous, or discontinuous. Discontinuous MMCs can be isotropic, and can be worked with standard metalworking techniques, such as extrusion, forging or rolling. In addition, they may be machined using conventional techniques, but commonly would need the use of polycrystaline diamond tooling (PCD).

Continuous reinforcement uses monofilament wires or fibers such as carbon fiber or silicon carbide. Because the fibers are embedded into the matrix in a certain direction, the result is an anisotropic structure in which the alignment of the material affects its strength. One of the first MMCs used boron filament as reinforcement. Discontinuous reinforcement uses "whiskers", short fibers, or particles. The most common reinforcing materials in this category are alumina and silicon carbide.[1]

Ford offers a Metal Matrix Composite (MMC) driveshaft upgrade. The MMC driveshaft is made of an aluminum boron carbide matrix, allowing the critical speed of the driveshaft to be raised by reducing inertia. The MMC driveshaft has become a common modification for racers, allowing the top speed to be increased far beyond the safe operating speeds of a standard aluminum driveshaft.

[gdmjoe]

More information...

FoMoCo Crown Victoria P71 data on the driveshafts:
*maximum Critical Speed (P225/60VRx16)


Aluminum Driveshaft


4.10 = 116mph
3.55 = 132mph
3.27 = 145mph
3.08 = 154mph


Metal/Matrix Driveshaft


4.10 = 133mph
3.55 = 154mph
3.27 = 167mph
3.08 = 177mph




*.attachment for associated TSB (Technical Service Bulletin)
.