Can Someone Boil this Driveshaft Stuff Down For Me?

[Wires]

Sorry to bring this up again - I've read a lot of other posts about this, but I can't figure out the answer. I tacked this on to another thread, but it really doesn't belong there. (Can it be deleted?)

If I understood Dennis correctly, a stock driveshaft is good up to the max goverend speed of a stock car -about 120.

Remove the speed limiter, and you can get yourself into trouble. Dennis mentioned cars that had the transmission problems, untill they began using the aftermarket driveshaft that he sells.

So, if you regularly drive above 120, the aftermarket driveshaft becomes more and more necessary. The problem is, nothing is black and white. Constant high speed driving, like the LEOs, obviously requires one. Constant driving at 55 obviously does not.

Now, if one installs 4:10 gears, that 120 becomes 103. (for the same driveshaft speed) That shifts everything down a bit.

My question is are my numbers correct? If I keep it in the double digits with my 4.10 gears, will I be OK untill I can comfortably afford the super-duper driveshaft that Dennis sells?

or

Should I squeeze somewhere and get one as soon as I can because even 100 is "too close." If getting the shaft keeps me from getting the shaft, (sorry, I just couldn't resist the bad pun) I'll find a way to "uncomfortably" afford it.

Thanks for putting up with me.

[BillyGman]

All I can tell you for certain, is that I've had the 3.55's, the 4.10's, and now the 4.56's in my Marauder, and once I installed the 4.56's, the stock driveshaft really produced a very obvious growling vibration at 90 MPH that progressively became louder the faster that I drove(above 90 MPH). It immediately was very noticeable even to my passengers.


However, I did NOT get that with the 4.10 gears at all while I had the stock driveshaft.

[FordNut]

Sorry to bring this up again - I've read a lot of other posts about this, but I can't figure out the answer. I tacked this on to another thread, but it really doesn't belong there. (Can it be deleted?)

If I understood Dennis correctly, a stock driveshaft is good up to the max goverend speed of a stock car -about 120.

Remove the speed limiter, and you can get yourself into trouble. Dennis mentioned cars that had the transmission problems, untill they began using the aftermarket driveshaft that he sells.

So, if you regularly drive above 120, the aftermarket driveshaft becomes more and more necessary. The problem is, nothing is black and white. Constant high speed driving, like the LEOs, obviously requires one. Constant driving at 55 obviously does not.

Now, if one installs 4:10 gears, that 120 becomes 103. (for the same driveshaft speed) That shifts everything down a bit.

My question is are my numbers correct? If I keep it in the double digits with my 4.10 gears, will I be OK untill I can comfortably afford the super-duper driveshaft that Dennis sells?

or

Should I squeeze somewhere and get one as soon as I can because even 100 is "too close." If getting the shaft keeps me from getting the shaft, (sorry, I just couldn't resist the bad pun) I'll find a way to "uncomfortably" afford it.

Thanks for putting up with me.
All MMs and all driveshafts are not created equal. Some will be fine with the stock shaft, at high speeds, with low gears. Some will have problems. Mine had a problem that I couldn't feel but it was enough of a vibration to cause the tranny rear seal to leak. I swapped to the dynotech MMX shaft and fixed it. Other members have had the stock shaft balanced at high speed and been successful in correcting a vibration problem. Some other members have used a carbon fiber shaft instead of the dynotech. Some have even gotten the old version CVPI shaft which was a MMX part from Ford. It is no longer available.

[BillyGman]

All MMs and all driveshafts are not created equal. Some will be fine with the stock shaft, at high speeds, with low gears. Some will have problems. That sounds about right to me.

[DeadVic]

See my post in this section from last night. my MM is spewing tranny fluid and is out of service. i will be doing what they said...getting a better driveshaft.

[RF Overlord]

Wires:

Read this article (http://www.mercurymarauder.net/forums/showthread.php?t=5163) by Ford transmission designer Jerry Wroblewski...

[BillyGman]

Don't you think that it still has something to do with the way a driveshaft is balanced also? I ask that, because even though this metal matrix aftermarket driveshaft that I've purchased directly from the Dynotech company does NOT cause vibration at 90 MPH with my 4.56 gears like the factory stock driveshaft did, it does cause it beginning at 120 MPH. I can live with that since I don't need to be driving faster than 120 MPH, but my point is that since the vibration is still there, and has simply been moved up another 30 MPH with this new driveshaft, then it must have something to do with the balance of the shaft also. Don't you think?

[Wires]

Ah ha. It's becoming clearer and clearer now.

Let's see if I've comprehended correctly:
(pardon some rounded numbers)

120 is the optimim top speed (car) for the stock driveshaft and stock (3.55) gears under ideal conditions. That's why the speed limiter is set there. This is due to the first harmonic resonance (string vibration, nodes at each end) and not balance issues.

Some cars have problems at lower speeds than this, some of which may be corrected by balancing. Others may be bad axle shafts and or pinion bearings, caused by the axle shafts. I think this happened to my car. I had all sorts of vibrations going on.

Going to 4.10 gears reduces the "ultimate speed limit" to about 100, but again, some cars will have problems at lower speeds.

There may or may not be a noticeable vibration to tell me that there is a problem.

BillyGman's 90 MPH vibration with 4.56s would be a 100 mph vibration with 4.10s and 120 with the stock 3.55s. Interesting. In his later post, he said that the aftermarket shaft still had the vibration at 120 with his 4.56s. So, that's 133 with 4.10s, and 154 with the stock gearing. As advetised, the aftermarket driveshaft has raised the resonant frequency.

OR, he may have a different problem causing this vibration - it could be a coincidence that the numbers work out so well with the known limitations of the stock driveshaft (as explained by Dennis) Or perhaps both explain his observations.

Now, my particular car seems to be fine at 90 MPH with 4.10s, that's 105 with stock gears. I can't tell if the vibration is front tires (which are terrible) or something else. I do know that when I had the axles and bearings changed (thanks, Ms. previous owner for not getting that done under warranty) I had MUCH less vibration.

SO, my particular bottom line, which may be different from others, is that I should order the driveshaft from Dennis as soon as I can afford it, but I shouldn't go to Title Max to do it. If I stay below 100, she should be just fine as is.

Unfortunately, no one knows where they are untill they have the dreaded puddle of tranny fluid - then you know that something has been wrong.

Thanks everyone for your help, and more feedback is encouraged.

[SergntMac]

Don't you think that it still has something to do with the way a driveshaft is balanced also? I ask that, because even though this metal matrix aftermarket driveshaft that I've purchased directly from the Dynotech company does NOT cause vibration at 90 MPH with my 4.56 gears like the factory stock driveshaft did, it does cause it beginning at 120 MPH. I can live with that since I don't need to be driving faster than 120 MPH, but my point is that since the vibration is still there, and has simply been moved up another 30 MPH with this new driveshaft, then it must have something to do with the balance of the shaft also. Don't you think?
No, I do not think it has anything to do with balance. Moreover, those among us who have had their OEM driveshaft "balanced" have done nothing to cure the problem at hand here. They may feel better about finding an inexpensive correction, but "balancing" is ineffective in addressing the real problem, driveshaft "whip."

The OEM driveshaft is balanced just fine, and it is suitable for safe and problem free use in a bone stock Marauder with 3:55 gears, because OEM programmed limiters prevent the car from reaching speeds where the OEM driveshaft "whips."

Imagine you are holding a long pole in hand, so long that the tips of the pole dip towards the ground when held horizontal to the ground. Now you rotate this pole at high speed, and while the center of the pole in your hands is stable, each end "whips" in ever increasing circles. This "whip' at each end is what tears up the tailshaft bearings and pinion bearing. This is due to the composition of the driveshaft, and it's Panther frame length. The material it's made from has a limit to how fast it can rotate before it deforms.

Once an owner changes rear end gear ratios, and adds a chip or custom tuning, the OEM limiters are void, and the drivershaft is allowed to rotate at speeds much higher than it can safely accommodate. I think it's safe to assume that because an owner has changed gears and added aftermarket tuning, it very likely he will drive the car beyond the limits of the OEM driveshaft. The DynoTech MMC driveshaft is constructed of material that has a higher "whip" tolerance, thus it cures the problem from our shared experience.

The MMC driveshaft has it's own "whip" point too, but it's much higher than the OEM shaft, and considered beyond our customary reach as owners/driver/racers, and fans of 4:10/4:30 gears. Therefore, you are correct to believe that your 4:56 gears have moved your MMC whip point closer to your reality. Your driveshaft is probably beginning to whip just about the time you reach your own operational limits, I would agree that your estimate of about 120 MPH is correct.

[MENINBLK]

Imagine you are holding a long pole in hand, so long that the tips of the pole dip towards the ground when held horizontal to the ground. Now you rotate this pole at high speed, and while the center of the pole in your hands is stable, each end "whips" in ever increasing circles.

Hey !!

I've seen the Blue Man Group do this !!! :)

[TooManyFords]

Imagine you are holding a long pole in hand, so long that the tips of the pole dip towards the ground when held horizontal to the ground. Now you rotate this pole at high speed, and while the center of the pole in your hands is stable, each end "whips" in ever increasing circles. This "whip' at each end is what tears up the tailshaft bearings and pinion bearing. This is due to the composition of the driveshaft, and it's Panther frame length. The material it's made from has a limit to how fast it can rotate before it deforms.I'm not sure, but the last time I checked our driveshafts are not held in the middle but at the ends. This analogy is incorrect for the problem being described. With that said, I think everyone understands what you are -trying- to say.

Now, my opinion is that it has -everything- to do with balance of the shaft. If the shaft were "perfectly" balanced, there would be no gyroscopic effect trying to throw the ends into an imperfect rotation around the center of the u-joint to cause it to "wobble" in the transmission tailshaft.

This is basic Physics.

john

[MM2004]

You are correct that the ends do not whip at high speeds. The center whips as centrifugal force acts upon the T.I.R. of the linear center of the driveshaft tubing.

The MMX driveshaft does indeed have a higher critical speed factor as it contains aluminum oxide instead of being coated as our OEM driveshafts.

Balance does have everything to do with vibration of a driveline. However, there are other factors inherent to a vehicle that amplifies 1st, 2nd and 3rd order vibration that may not be driveshaft related specifically, but a number of contributing factors. It is common to blame driveshaft as the root cause because it is the least expensive drivetrain component and is designed to fail under certain and extreme conditions.

The driveshaft can be balanced but in a "bent" state. It may not vibrate, but will cause pre-mature joint failure as it is not spinning on a true center-line.

Just my :twocents:.

Mike.


I'm not sure, but the last time I checked our driveshafts are not held in the middle but at the ends. This analogy is incorrect for the problem being described. With that said, I think everyone understands what you are -trying- to say.

Now, my opinion is that it has -everything- to do with balance of the shaft. If the shaft were "perfectly" balanced, there would be no gyroscopic effect trying to throw the ends into an imperfect rotation around the center of the u-joint to cause it to "wobble" in the transmission tailshaft.

This is basic Physics.

john

[dwasson]

So does this mean that a two-piece driveshaft, one with a center bearing, will be inherantly less prone to this first order harmonic? And if that is the case, what is the underlying reason? Is it because the shorter segments of the driveshaft raise that harmonic frequency to such a high level that it isn't an issue? Or, is because the shortening the driveshaft segments means that the forces of the ends whipping are lessened?

[MM2004]

The center bearing that attaches to the under carriage consists of rubber that is designed to dampen or resonate at a certain frequency.

The key element is the shorter tube length that is directly related to critical speed factors. Along with the dampening effects of the CB/assy.

I have been in OEM vehicles (before they left the customer's plant) with NVH issues that did not vibrate the vehicle by feel, but the noise sounded as if a jet were directly in front of us running at WOT.


So does this mean that a two-piece driveshaft, one with a center bearing, will be inherantly less prone to this first order harmonic? And if that is the case, what is the underlying reason? Is it because the shorter segments of the driveshaft raise that harmonic frequency to such a high level that it isn't an issue? Or, is because the shortening the driveshaft segments means that the forces of the ends whipping are lessened?

[SergntMac]

You are correct that the ends do not whip at high speeds. The center whips as centrifugal force acts upon the T.I.R. of the linear center of the driveshaft tubing.

The MMX driveshaft does indeed have a higher critical speed factor as it contains aluminum oxide instead of being coated as our OEM driveshafts.

Balance does have everything to do with vibration of a driveline. However, there are other factors inherent to a vehicle that amplifies 1st, 2nd and 3rd order vibration that may not be driveshaft related specifically, but a number of contributing factors. It is common to blame driveshaft as the root cause because it is the least expensive drivetrain component and is designed to fail under certain and extreme conditions.

The driveshaft can be balanced but in a "bent" state. It may not vibrate, but will cause pre-mature joint failure as it is not spinning on a true center-line.

Mike.Thanks Mike! So...We can all keep our money in the bank and get our OEM driveshafts balanced for probably under 100 bucks, rather than purchase a DynoTech MMC driveshaft at 525.? Cool! Oh, BTW, is there any difference between the "MMX" driveshaft you mention, and the "MMC" driveshaft from DynoTech otherwise mentioned here?

Jeeze y'all, I'm real sorry I posted that crap about "whip", what a big waste of time for y'all in reading it. I'll delete it later, and I promise not to do this again. I'm real glad to see professional opinions on the topic come to the surface, wish y'all were here a few years ago.

I posted my "whip" analogy/metaphore on behalf of our members here who may not grasp all of the finer points of the technical discussion from Jerry W, posted by RFOverLord. I only meant to inspire some understanding for the common owner, not explain in exacting detail what often follows a gear swap and custom tuning. I wanted to help make it better understood that the problem is not as simple as resolving a front end vibration by balancing tires, and I appreciate my redirection. I'm happy it was caught before anyone acted on my advice. Best leave this stuff to the experts, eh?

It was also said ^ there, that every driveshaft is different, some owners will experience problems, others will not. I agree.

Presently, I own the Kenny Brown #1x, which came with a DynoTech MMC driveshaft installed at delivery. I didn't make this upgrade decision, but, I did own a 300A prior to this particular MM.

Way back then, I took the advice of senior owners here and bought a DynoTech MMC driveshaft after I upgraded to 4:10s, and SCT tuning. I didn't really ask a lot of questions, just did what was recommended by the lead honchos posting here at the time. Later on, I engaged one of them in a discussion about the "need" to buy this upgrade, and this exchange caused me to restore my OEM Marauder driveshaft, and investigate his promise of certain vibration.

I found nothing. I ran my MM on the highway over 120 MPH and stood underneath it while it ran 120+ MPH on a dyno. Nada, zip, zero, bupkis vibration, or, other NVH related problems through 6200 RPM. It's history now, money spent and forgotten about. But...Did I need to buy this driveshaft back then? No.

This experience sent me on my mission to explore and test all recommendations made to owners here. I continue in this mission today, and ever since way back then, my advice to fellow owners here has been to test before you buy. It's this simple.

Thanks again, guys!

[Directedby]

I have stock driveshaft with 4:10 gears.

No vibration - fastest I have gone with 4:10's is 100MPH.

[MM2004]

[QUOTE=SergntMac]Thanks Mike! So...We can all keep our money in the bank and get our OEM driveshafts balanced for probably under 100 bucks, rather than purchase a DynoTech MMC driveshaft at 525.? Cool! Oh, BTW, is there any difference between the "MMX" driveshaft you mention, and the "MMC" driveshaft from DynoTech otherwise mentioned here?

Honestly, I am unsure. Metal Matrix Composite (MMC) is what I found from critical speed documentation in my e-mail archives from work in my Quality Control days. This composite is a damn good driveshaft. But, unless you plan on traveling at 100+ mph for extended periods of time, I don't feel this investment is worth it.

A balance check would be the way I would travel if I were experiencing vibration issues, once the tires were verified as balanced. Low U-joint articulation will eventually affect balance as well, and continue to worsen as the U-joints wear. Replacing these can also improve vibration issues (if executed correctly).

Here's what I found this evening:

<TABLE borderColor=#064c01 cellSpacing=1 cellPadding=2 width=561 border=1><TBODY><TR><TD width="36%" bgColor=#ffffff height=16>
Crown Victoria
















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ALUM
















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ALUM G
















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MMC
















</TD><TD width="12%" bgColor=#ffffff height=16>
ALUM
















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ALUM
















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Enter Outside Diameter
















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3.5
















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3.5
















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3.5
















</TD><TD width="12%" bgColor=#ffffff height=16>
4.0
















</TD><TD width="12%" bgColor=#ffffff height=16>
3.75
















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Enter Tube Thickness
















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0.083
















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0.083
















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0.083
















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0.083
















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0.083
















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Enter Centerline Distance
















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55.6
















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55.6
















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55.6
















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55.6
















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55.6
















</TD></TR></TBODY></TABLE>
<TABLE borderColor=#074c01 cellSpacing=1 cellPadding=2 width=561 border=1><TBODY><TR><TD width="36%" bgColor=#ffffff height=16>
Critical Speed
















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6727
















</TD><TD width="12%" bgColor=#ffffff height=16>
6787
















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7639
















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7711
















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7219
















</TD></TR></TBODY></TABLE>
<TABLE borderColor=#024c01 cellSpacing=1 cellPadding=2 width=561 border=1><TBODY><TR><TD width="36%" bgColor=#ffffff height=16>
Safety Factor (129 mph)
















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12%
















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13%
















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27%
















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28%
















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20%
















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<TABLE borderColor=#0c4c01 cellSpacing=1 cellPadding=2 width=561 border=1><TBODY><TR><TD width="36%" bgColor=#ffffff height=16>
Safety Factor (135 mph)
















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7%
















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8%
















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21%
















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23%
















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15%
















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<TABLE borderColor=#104c01 cellSpacing=1 cellPadding=2 width=360 border=1><TBODY><TR><TD width="56%" bgColor=#ffffff height=16>
Axle Ratio
















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</TD><TD width="19%" bgColor=#ffffff height=16>
3.55
















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3.55
















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I posted a while back about making a 4.0" driveshaft for my MM. I don't need it at the moment and need to verify if there is floor pan clearance during vehicle "jousting" before recommending this route.

I hope this clears up suspicions on our driveshaft integrity/capabilities.

BTW, Most driveshafts for OEM are balanced between 3,000 - 4,000 rpm.

For many years, I balanced driveshafts using the exact same machines as DynoTech. Gotta' love that, eh? :)

Mike.

[MI2QWK4U]

When I did the open track at MIS event last year, I had the Marauder up over 100 mph the entire time I was on the oval, for the most part around 135-140 mph, a few times I went higher than that, all the way up to the highest of appx 155 mph. No vibration, no tailshaft leaks. What I was told by Lidio was to have the shaft balanced and call it a day, but since I never had a problem, I never bothered. Lidio had his balanced, but it was right on and needed no adjustments. Its all about how well it is balanced, some of us just got lucky i guess.