Tail shaft failure

[Dennis Reinhart]

For those that think the stock Marauder drive shaft is safe after the cars speed limiter is removed, this might change your mind, this happened on the dyno at 130 MPH, fortunately the transmission was not damaged other than the tail shaft, and this tail shaft had the forced lube kit installed.

http://web.iwebcenters.com/reinhartautomotive/images/session/00-00-1250361155-tailshaft.jpg

http://web.iwebcenters.com/reinhartautomotive/images/session/00-00-1250361180-tailshaft1.jpg

[-Matt-]

ouch, so what are ya going to do now? lol

[Marauderjack]

You couldn't feel it on the dyno Dennis???:confused:

[Dennis Reinhart]

You couldn't feel it on the dyno Dennis???:confused:


No Jack, I am data logging the car, watching air fuel, and a dyno run lasts less than a minute, so he got a new tail shaft and a drive shaft. I did a Chevy Avalanche years ago, we installed a SC and tuned the truck and at 120 it twisted the drive shaft in two pieces, it slung a U joint cap across the room and embedded it in the wall, that drive shaft was paper thin with foam in the middle of it, and it took out the out put shaft on that transmission, this is the first I have seen on a Marauder. But I do know the FHP had three failures prior to going the the MMDS.

[Marauderjack]

Dang!!:eek:

You need to wear a suit of armor to dyno modern junk then!!:cool:

Y'all be careful down thar!!:cool4:

[ImpalaSlayer]

damn thats pretty crazy

[Benwin]

Holy ****... Was there any damage to the car (aside from the obvious mechanical damage)?

Note to self... When I get my marauder and get it S/C, make sure I get the racing transmission conversion, and a strong drive shaft...

O.o

[Glenn]

Maraudersanta (David) had the exact same situation on his '04 DTR NA MM at Team Ford a few years ago. The only mods were a FRPP shorty exhaust system and UDPs. First pull on the dyno and the trans tail shaft housing cracked. I was there and it was a distinct crack sound. Fortunately, it did not blow as bad as Dennis' did. The drive shaft was OK. Hard to understand how these things blow when you have no noticable high speed vibrations? A weak housing or factory defect?

Glenn

[Joe Walsh]

Maraudersanta (David) had the exact same situation on his '04 DTR NA MM at Team Ford a few years ago. The only mods were a FRPP shorty exhaust system and UDPs. First pull on the dyno and the trans tail shaft housing cracked. I was there and it was a distinct crack sound. Fortunately, it did not blow as bad as Dennis' did. The drive shaft was OK.
Hard to understand how these things blow when you have no noticable high speed vibrations? A weak housing or factory defect?
Glenn

And just imagine the stress involved when you can feel a driveline vibration...:eek:

[LANDY]

http://i288.photobucket.com/albums/ll166/lizz629/100_1818.jpg

http://i288.photobucket.com/albums/ll166/lizz629/100_1819.jpg

first of all. thanks Dennis Reinhart, for all your help and with my driveshaft at the begining of this week. and i apologize for being a p.i.t.a. about the tracking #s. well driveshaft got here yesrerday i installed it, drove it, great. finally feels like a marauder again at highway speeds. also did the j-mod, i really like the way it shifts, feels like a whole new car.
this is what happened to mine at 120mph

[lincolnpimp]

This also happened to me!!!! One tail shaft mod and a drive shaft from DR and all is well!!!!!

[ImpalaSlayer]

man i never herd of this now theres 3 of you?

[LANDY]

man i never herd of this now theres 3 of you?
it just happened to me about a week and 1/2 ago. but before that when the car was under extended warranty tailshaft seal broke 3 times and i took it to ford. (never again) dont understand why people fix the broken but not the problem thats causing it.

[LIGHTNIN1]

Thanks Dennis for warning us about this. Its one of those things you may not think about till it happens. I will check into it.

[MM2004]

Dennis,

Pics of the driveshaft?

Mike.

[tjl006]

This is my tailshaft, it is modefied with the force lube mod and I have a four inch aluminum driveshaft. Both are from bc automotive. Darrin says the bushing was defective in the tailshaft housing. When I took the housing off I noticed the small part on the right was broken off I thought I may of dropped it and not reliazed it. This thread is making me rethink that assumption.

[ImpalaSlayer]

so when this occurs. does the DS go rouge?

[LANDY]

ibelieve the high speed that were given to the DS made it wobble and thats what occurs. plus you should be able to feel vibration before it happens. mine started 115mph and i took it to 122mph, then i saw smoke on my rear view mirror and stopped.

[Dennis Reinhart]

Maraudersanta (David) had the exact same situation on his '04 DTR NA MM at Team Ford a few years ago. The only mods were a FRPP shorty exhaust system and UDPs. First pull on the dyno and the trans tail shaft housing cracked. I was there and it was a distinct crack sound. Fortunately, it did not blow as bad as Dennis' did. The drive shaft was OK. Hard to understand how these things blow when you have no noticable high speed vibrations? A weak housing or factory defect?

Glenn

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 (http://www.mercurymarauder.net/forums/showthread.php?t=5163&highlight=metal+matrix+drive+s haft#). 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 (http://www.mercurymarauder.net/forums/showthread.php?t=5163&highlight=metal+matrix+drive+s haft#) 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.

[LANDY]

thats an awsome article of how things work. thanks again.
:cool4: LANDY

[Stranger in the Black Sedan]

This is why I picked up a P71 MMC TSB replacement shaft for $65 a couple weeks ago. Cost $1300 new from Ford when you could still get them. Direct fit for the MM and it is a metal matrix shaft

[twin03]

Damn, if that happened to me, I would have **** on myself....

[babbage]

This is why I picked up a P71 MMC TSB replacement shaft for $65 a couple weeks ago. Cost $1300 new from Ford when you could still get them. Direct fit for the MM and it is a metal matrix shaft


Yeah, now you just have to install it. :D

And Glenn always says the factory shaft is fine. :rolleyes:

maximum Critical Speed (16 inch wheels)
--------------------------------------
CVPI Amuminum Driveshaft 4.10 = 116mph
CVPI Amuminum Driveshaft 3.55 = 132mph
CVPI Amuminum Driveshaft 3.27 = 145mph
CVPI Amuminum Driveshaft 3.08 = 154mph
CVPI Metal/Matrix Driveshaft 4.10 = 133mph
CVPI Metal/Matrix Driveshaft 3.55 = 154mph
CVPI Metal/Matrix Driveshaft 3.27 = 167mph
CVPI Metal/Matrix Driveshaft 3.08 = 177mph

MMC's elasticity is nearly 1.5 times that of 6061 aluminum, this allows the MMC shaft to absorb more drive-line vibrations. The issue with shafts is that they create ultra high frequency vibrations at high rpms, and they will eventually self-destruct. It also absorbs shaft "twist" much better.

The 53" police MMC shaft's critical speed is 9093 rpm, and the aluminum shaft is 7930 rpms.

[LANDY]

point is get a dynotech spend the money thrust me is worth it. not comercializing just personal experience

[bawazir]

so Now i have to buy DS? Can you guys give me the part# or any aftermarket DS i could buy?
I am doing my 4.10 this week, so am thinking the Drive Shaft with it

[SC Cheesehead]

so Now i have to buy DS? Can you guys give me the part# or any aftermarket DS i could buy?
I am doing my 4.10 this week, so am thinking the Drive Shaft with it

You can do the initial 4:10 install without the driveshaft. Would be a good idea to install a new driveshaft at a later date, especially if you plan on running at higher speeds.

More important, do you have an X-Cal with a new shift schedule for the 4:10s that you can upload after the install? If not, be prepared for a less than impressive driving experience.

[bawazir]

You can do the initial 4:10 install without the driveshaft. Would be a good idea to install a new driveshaft at a later date, especially if you plan on running at higher speeds.

More important, do you have an X-Cal with a new shift schedule for the 4:10s that you can upload after the install? If not, be prepared for a less than impressive driving experience.


soo do i need a new shaft? dose that mean i have to buy a stock new shaft, or like performance shaft?

I only have about 40,000 miles on the car..

thanks

[SC Cheesehead]

soo do i need a new shaft? dose that mean i have to buy a stock new shaft, or like performance shaft?

I only have about 40,000 miles on the car..

thanks

I've had 4:10s installed in my car since March 2007, still running the OEM driveshaft. Lots of opinions on the driveshaft issue. I rarely drive the car over 75 mph, so I've not had any problems to date; not to say that I won't, just haven't had any so far.

If I can find a decent used CVPI driveshaft for a reasonable price I'll prolly pick it up, until then, I'll stay with the stock unit.

Regarding your tune, you didn't say if you have a new tune to go along with the gears. I repeat, if you go with 4:10s but don't adjust your shift schedule for them, the car will run like crap.

[fastblackmerc]

I've had 4:10s installed in my car since March 2007, still running the OEM driveshaft. Lots of opinions on the driveshaft issue. I rarely drive the car over 75 mph, so I've not had any problems to date; not to say that I won't, just haven't had any so far.

If I can find a decent used CVPI driveshaft for a reasonable price I'll prolly pick it up, until then, I'll stay with the stock unit.

Regarding your tune, you didn't say if you have a new tune to go along with the gears. I repeat, if you go with 4:10s but don't adjust your shift schedule for them, the car will run like crap.

Rex, he's been told that many times.... just falling on deaf ears. I have an extra stock MM driveshaft that I'm getting balanced. It's not a MMX driveshaft but I don't go north of 90 too often.

[Ms. Denmark]

What would a custom carbon fiber shaft go for? From what I gather there is little concern for critical speed with the CF shafts. Is my understanding correct?

[offroadkarter]

What would a custom carbon fiber shaft go for? From what I gather there is little concern for critical speed with the CF shafts. Is my understanding correct?


Call this place or email them about a carbon fiber shaft

http://www.dynotechengineering.com/home.htm

Someone off CVN has one in his 2002 grand marquis and he hasn't had any issues with it...

[SC Cheesehead]

I did a quick search and it looks like anywhere from $700 to $900 for a CF driveshaft in Marauder length.

[Dennis Reinhart]

Call this place or email them about a carbon fiber shaft

http://www.dynotechengineering.com/home.htm

Someone off CVN has one in his 2002 grand marquis and he hasn't had any issues with it...


The 4" T5 6061 is what I use now there about 550.00

[Spectragod]

This thread reminds me that I need to call Dennis and order a new DS...

[SC Cheesehead]

The 4" T5 6061 is what I use now there about 550.00

I'm no expert, but from what I've gathered so far, the 6061 metal matrix composite will do the trick for a whole bunch cheaper than carbon fiber unless you're looking at real severe service application.

[FordNut]

I'm no expert, but from what I've gathered so far, the 6061 metal matrix composite will do the trick for a whole bunch cheaper than carbon fiber unless you're looking at real severe service application.

It's a 4" 6061, but not MMC

[RR|Suki]

I got a CVPI one for $75 we'll see if I ever break anything

[offroadkarter]

I did a quick search and it looks like anywhere from $700 to $900 for a CF driveshaft in Marauder length.



They do say its not recommended for daily driving, because of large stones or anything possibly hitting the shaft and cracking it, but the guy i know that has it daily drives his MGM and hasn't had any issues like that...


But, Ms. D doesn't daily drive the MM anymore anyways :D




And i think his is a different brand, PST, here's some photos....


http://www.supermotors.net/registry/2315/22800

http://www.supermotors.net/getfile/174172/original/pict29.jpg
http://www.supermotors.net/getfile/174195/original/pict66.jpg

[SC Cheesehead]

+1 to Ryan's comments. IMO, CF is prolly overkill for most of our applications.

[offroadkarter]

+1 to Ryan's comments. IMO, CF is prolly overkill for most of our applications.


Its always better to build it to strong than not strong enough :D



Although 700-900 is alot to pay....

[FordNut]

Its always better to build it to strong than not strong enough :D



Although 700-900 is alot to pay....

About what I paid for my Mark Williams custom 4" MMC shaft.

[ntd]

From what I've heard one well placed pebble and you looking a spectacular failure with CF driveshafts as they don't bend or dent they splinter when they fail. I would have my stock one balanced or give Dennis a call for my street car. On a race care go for the CF if you got the money

[offroadkarter]

From what I've heard one well placed pebble and you looking a spectacular failure with CF driveshafts as they don't bend or dent they splinter when they fail. I would have my stock one balanced or give Dennis a call for my street car. On a race care go for the CF if you got the money


I've heard of things happening to stuff to from other people that know people who read things on the internet...



Quickcrownvic runs a PST shaft in his lightning powered crownvic that he daily drives in florida, his has held up just fine

BK_marquis has one on his 2002 grand marquis which he autocrosses and daily drives in new jersey, his has held up fine

[ntd]

I've heard of things happening to stuff too from other people that know people who read things on the internet...


If your going to be a smart a$$ you should at least be smart first:shake:, I corrected your grammar for you.

Any manufacture will state not for street use. I would trust the people that make them and especially not you grand poobah of all things technical.

[MrBluGruv]

Everything I've heard about CF is that it is EXTERMELY resilient to damage and breakage, but if it does so much as crack, it's allllllll over....

[offroadkarter]

If your going to be a smart a$$ you should at least be smart first:shake:, I corrected your grammar for you.

Any manufacture will state not for street use. I would trust the people that make them and especially not you grand poobah of all things technical.



Sorry grammar nazi


Lots of manufacturers list "not for street use" and people do it anyways.... Xenon bulbs, offroad X pipes, they are all "for offroad use only" that to cover their ass when people get busted for having them....


Why not ask your Marauder god reinhart what he thinks, i'm sure he'd love to sell you any driveshaft.... You might get the whole thing in one box to!

[dohc324ci]

Man I may have to keep her under 120 this scares me. I'll have to put this sooner in my project list.

[Dereck]

Hi Dennis Reinhart

Would making a driveshaft with a center bearing assembly be any help in saving the tailshaft housing?

Obviously the bearing and extra joint would add mass to the driveshaft but I was wondering if the "two" shorter driveshafts and rubber center bearing mount would help absorb vibrations.

Regards

Dereck

[ntd]

Sorry grammar nazi


Lots of manufacturers list, "not for street use" and people do it anyways.... Xenon bulbs and offroad X pipes, they are all (")not needed for offroad use only(")not needed (that)not needed to cover their ass when people get busted for having them....


Why not ask your Marauder god Reinhart what he thinks, I'm sure he'd love to sell you any driveshaft.... You might get the whole thing in one box to!

I'm actually not very good at grammar just have common sense and good spell check. Xenon bulbs and offroad X pipes they have nothing to do with the failure of a CF(carbon fiber) or any driveshaft which would be a little more eventful than a burnt out bulb or exhaust leak:rolleyes:. Are you sure you know what CF is or what a driveshaft does, your comments seems a little out of context. As for Dennis being a God whatever gets you off:dunno:, I see him as a person that has a company that sells automotive parts(which is why I'm sure he would love to sell me parts and maybe all in one box). Not that I don't like him or his parts I currently haven't bought any parts from him yet. Oh and I fixed your grammar for you:beer:.

[Stranger in the Black Sedan]

two shorter driveshafts, like trucks use, would give each smaller, lighter driveshaft a much higher critical speed. However have fun making that work on our chassis. And then you have added a ton of mass to the driveline overall w/ the extra slip yoke and the multiplicity of u joints. I had joked that the Marauder driveshaft is so long that it should have been 2 piece from the factory. Actually some 4th gens did use a 2 piece driveshaft from the factory.

[Dennis Reinhart]

You can buy from who ever you want to, I would never use a two piece drive shaft why do you think all the Mustang guys got away from them? and who do you think made the 4" T5 6061 single piece to replace them, Dyntotech. Not many here need nor can afford a 700.00 Carbon fiber shaft.