125 MPH Vibration

**tbone** · 11-23-2010, 08:10 PM

I was on the backroads in downstate I$@&*%*s this morning and had a chance to open her up on a long straightaway to 125, with plenty more left, when a small vibration started, so I shut her down.
Is this the driveshaft issue I've heard about? Is this the typical speed it starts at? Is the only fix a special (expensive) aluminum/hybrid driveshaft?

(Yes, I did it in a remote area with no side streets, traffic, hills, etc.)

**MM03MOK** · 11-23-2010, 08:18 PM

The fix is not to go that fast.

That's cheaper than replacing or balancing your drive shaft.

**FormulaMarauder** · 11-23-2010, 08:21 PM

Anything can create a little vibration at those speeds such as tire pressure, loose suspension, and driveshaft wobble. If you're not traveling at that speed often, which I hope you are not, then I wouldn't worry.
Also check your flux capacitor, muffler bearings, and headlight fluid to make sure they are all in working order.

**tbone** · 11-23-2010, 08:22 PM

Ok, I was in Utah on the salt flats this morning.............

**tbone** · 11-23-2010, 08:26 PM

It's not that I want to travel at that speed often, not the point.

A lot of cars are designed to travel at high rates of speed, for instance on the autobahn. They make the cars perform at these speeds. Maybe I want to go to Montana and go as fast as I want. Maybe I want to ship my car to Europe. I'm just curious about the technical aspects of what is going on here.

**Joe Walsh** · 11-23-2010, 08:27 PM

If it didn't start until you hit @ 125.....driveshaft.

Too much of that and your rear transmission seal will give up the ghost.

**ChiTownMaraud3r** · 11-23-2010, 08:27 PM

Never felt it on my '04 at even faster than that..not a pleasant feeling I bet.

**FordNut** · 11-23-2010, 08:30 PM

True, but that is the driveshaft symptom. The solution is not just an aluminum driveshaft, as the Marauder came from the factory with one. The solution is a metal matrix driveshaft, or a 4" aluminum one. Metal matrix has a different metallic structure from regular aluminum. The problem is they're hard to find. Dynotech used to sell one but they no longer have it, they sell a 4" regular aluminum one. The diameter, material, length all figure in to determine the critical speed of the driveshaft.

Interesting factoid, the critical speed applies to any rotating cylinder, it was a big problem with gas centrifuge development. Lots of the early models ran at sub-critical speeds (like putting the speed limiter in the stock MM program), it took years for the scientists to figure out how to get them to rotate at supercritical speeds. It's sort of like harmonic frequency in RF electronics. First critical speed is like a bow, second critical speed is like a S, 3rd critical speed has 3 bows, etc...

**DOOM** · 11-23-2010, 08:31 PM

I have had my marauder at 150+ MPH several times and have never felt any types of vibration at all.

Also my 01 CVPI I have had at 140MPH on more than one occasion with no issues.

Now I have a 05 CVPI without any vibration issues at all.

**tbone** · 11-23-2010, 08:31 PM

I'll peak at the seal tomorrow and see. I shut it down right away, so probably not an issue.
No, not a good feeling.

**tbone** · 11-23-2010, 08:34 PM

Originally Posted by FordNut

True, but that is the driveshaft symptom. The solution is not just an aluminum driveshaft, as the Marauder came from the factory with one. The solution is a metal matrix driveshaft, or a 4" aluminum one. Metal matrix has a different metallic structure from regular aluminum. The problem is they're hard to find. Dynotech used to sell one but they no longer have it, they sell a 4" regular aluminum one. The diameter, material, length all figure in to determine the critical speed of the driveshaft.

Interesting factoid, the critical speed applies to any rotating cylinder, it was a big problem with gas centrifuge development. Lots of the early models ran at sub-critical speeds (like putting the speed limiter in the stock MM program), it took years for the scientists to figure out how to get them to rotate at supercritical speeds. It's sort of like harmonic frequency in RF electronics. First critical speed is like a bow, second critical speed is like a S, 3rd critical speed has 3 bows, etc...

What do they do with driveshafts designed for the autobahn?

**FordNut** · 11-23-2010, 08:34 PM

My car never vibrated that I could feel, but it did cause trans seal leakage. This was after 4.10 gears were installed. Upgraded driveshaft fixed it.

**Joe Walsh** · 11-23-2010, 08:35 PM

Originally Posted by DOOM

I have had my marauder at 150+ MPH several times and have never felt any types of vibration at all.

Also my 01 CVPI I have had at 140MPH on more than one occasion with no issues.

Now I have a 05 CVPI without any vibration issues at all.

Jake, your CVPI's came with the high speed/metal matrix driveshaft.
You can't feel the vibration in your Marauder because once you punch it the rear wheels never touch the pavement again!....

**FordNut** · 11-23-2010, 08:36 PM

High speed driveshafts can be made of carbon fiber, metal matrix aluminum, or have a carrier bearing in the middle of the shaft.

**tbone** · 11-23-2010, 08:37 PM

Originally Posted by DOOM

I have had my marauder at 150+ MPH several times and have never felt any types of vibration at all.

Also my 01 CVPI I have had at 140MPH on more than one occasion with no issues.

Now I have a 05 CVPI without any vibration issues at all.

Did you have your driveshafts balanced or are you just lucky?

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