how bad is the vibration

It seems like it would vary between individual cars. My stock 3.08 car vibrates a little bit in the 110+ range, my friend's car vibrates noticibly worse.
 
MediumD said:
It seems like it would vary between individual cars. My stock 3.08 car vibrates a little bit in the 110+ range, my friend's car vibrates noticibly worse.
Click to expand...


yea, consider how much vibration you get goin that speed with stock gears, now...multiply that.
 
The vibes with stock 2 piece driveshaft and 4.10s for example, are unbearable.

The logic that if you don't have any vibration now up to whatever MPH, then you won't have it with gear change is a myth.
 
m_maker said:
The logic that if you don't have any vibration now up to whatever MPH, then you won't have it with gear change is a myth.
Click to expand...

Explain exactly why that is. If you don't get vibration at 110 with 3.08s there is no reason I can think of that you would get vibration below 80 with 4.10s.
 
Jerry mentions a lot of possible causes for a vibration. The driveshaft seems to be the main culprit, or at least I'll assume it is since people are making metal matrix shafts, and I'm not reading anything about fixes for the other potential causes.

The driveshaft vibration is produced when a part of the shaft is trying to spin outwards due to inertia, and the force peaks at a certain RPM. It does not seem like it would matter at what vehicle speed this happens, just what driveshaft rotation speed. If the shaft is not vibrating at 110mph, switching to 4.10s and 80mph would not affect the shaft speed and thus shouldn't affect shaft vibration.
 
Gears most definitely spin the ds faster, WAY faster then stock, when you install gears on an already vibrating car it enhances it dramatically.
 
MediumD said:
The driveshaft vibration is produced when a part of the shaft is trying to spin outwards due to inertia, and the force peaks at a certain RPM. It does not seem like it would matter at what vehicle speed this happens, just what driveshaft rotation speed. If the shaft is not vibrating at 110mph, switching to 4.10s and 80mph would not affect the shaft speed and thus shouldn't affect shaft vibration.
Click to expand...


the force may peak, but that does not mean that the vibration dies down after that peak, it is still present, but the vibration comes arround faster, the faster you go, so realy...it does get worse and worse.
 
Obviously gears are going to make the driveshaft spin faster. Simple math can determine how much faster.

MrWilson said:
the force may peak, but that does not mean that the vibration dies down after that peak, it is still present, but the vibration comes arround faster, the faster you go, so realy...it does get worse and worse.
Click to expand...

The total force continues rising, yes. However the felt vibration force peaks because, as explained by Jerry:

A car has what's called a first order driveline bending point. To explain it simply, if you are holding both ends of a shaft fixed and rigid, and spin the shaft, there is centrifigual force, from the weight of the shaft, that, as you spin the shaft faster and faster, the middle of the shaft wants to whip or spin in a much larger circle than the ends of the shaft. Make sense?

Now, from an engineering standpoint, the first order resonance point is when the displacement of the middle is it's greatest. This is NOT at the fastest speed you can spin the shaft. Ever have a tire out of balance and it's really bad at 60 mph but better at 80 mph? Well, what happens to a shaft is at a certain speed (based on stiffness of the shaft, length and weight) you have one speed with the highest displacement in only one point. If you spin the shaft faster, the displacement of the shaft now happens in two points, but the amplitude of each "node" is less. If you spin it even faster, then you get 3 nodes, and etc.
Click to expand...
 
Yeah well you should have taken a ride in the MANY cars we have geared before we figured ouut the MMXDS deal. We have run them into the triple digit's and it was SO BAD you thought you were going to die. I don't care what anybody writes. I know what I know first hand.
 
I can't agree more with geno.



Even IF you have other things causing your vibes, An MMX shaft will solve one of the biggest causes of it. I have an unholy vibration comming from the shaft in my 98 right now. I don't know why as it is stock geard, but ever it acts just like the shaft is out of balance. I have an extra MMX shaft sitting in my closet, which I hope will fix the problem.


Mike
 
For the record I don't think anyone is disagreeing than an MMX shaft will help quite a bit with vibration if not cure it. Still, if it doesn't vibrate at 110 with 3.08s, it won't at 80 with 4.10s.
 
ok buddy, two personal cases:

95 Mark VIII stock gears stock driveshaft - ZERO vibes up to 132mph.

same car with OEM FORD 4.10 gears/t-lok stock driveshaft - unbearable vibes at 80-85mph, quieting down around 90, even worse at 100+.

97 Mark VIII stock gears stock driveshaft - ZERO vibes up to 135mph.

same car with OEM FORD 3.73 gears/t-lok stock driveshaft - even worse than the 95 at the same speeds

I tried saving the money and keeping the stock driveshaft even after learning of the first car. But to no avail. Both cars recevied MMX driveshafts, one from Denny's, one from Dynotech. Vibration is gone, up to 155mph.
 
I had the stock 2 piece driveshaft in my 95 LSC with 4.30 gears... there was vibration at 80mph but nothing to lose sleep over in my opinion. But I wouldn't do the same mod on the 98 LSC because the 95 LSC was more dragged out.
 
m_maker said:
ok buddy, two personal cases:

95 Mark VIII stock gears stock driveshaft - ZERO vibes up to 132mph.

same car with OEM FORD 4.10 gears/t-lok stock driveshaft - unbearable vibes at 80-85mph, quieting down around 90, even worse at 100+.

97 Mark VIII stock gears stock driveshaft - ZERO vibes up to 135mph.

same car with OEM FORD 3.73 gears/t-lok stock driveshaft - even worse than the 95 at the same speeds

I tried saving the money and keeping the stock driveshaft even after learning of the first car. But to no avail. Both cars recevied MMX driveshafts, one from Denny's, one from Dynotech. Vibration is gone, up to 155mph.
Click to expand...

Ok, now figure out why that would be and that would mean something.
 
You must log in or register to reply here.

Members online

Total: 144 (members: 1, guests: 143)
Back
Top