Vibration from shifter @ high-rpm's in 3rd+ gears only !!
 

I've got a vibration/sound problem, only starts to happen really excessively in 3rd gear..

1st gear is fine upto 5500 rpm
2nd gear starts to make this metallic sound along with a bit of shifter vibration above 4500 rpm
3rd gear starts to make more of the sound and vibrations above 4000 rpm +
4th starts around 3500 rpm..
5th starts to make the same around 3250 rpm.

but, low rpm's, coasting, or revving down doesn't cause the sound/vibration. This is really really loud when I'm racing someone and shifting @ 4800 in 3rd, 4th, etc..

So, is it the driveshaft? Clutch? Clutch forks? Nothing has been done recently to the drivetrain (mod-wise) so I'm stuck for answers..

Thanks !!

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94 GT (triple black)
K&N, FMS 9mm, FMS 95 17" Cobra R's, 3.27, 12* timing, MSD Coil, 180* thermostat, MAC Shifter/Gauges/Pedals, Euro Clear Projectors & Corners
My CAR!
Email me: jetuomi@yahoo.com

http://www.mustangworks.com/msgboard...ML/020115.html

Okay, could my problem be fly-wheel related??

Mine was machined by a shop over 4 months ago, maybe they were off on their work, and now as the clutch is being worked in, its starting to show the above problems??

Thanks..

SOUNDS LIKE MAIN SHAFT IN TRANNY IS BENT. My 85 gt did that and i found the main shaft had a runout of .014

It's the U joints in your driveshaft. The shifter shakes horribly and when you hit a really high RPM in 4th you hear what sounds like a helicopter landing on your car. It makes a WHOOP WHOOP WHOOP kinda deep vibrational sound.

I had the same problem, I got the FMS aluminum driveshaft, it comes with beefy 1330 U joints. Its worth the 160 bucks. It will make your everyday drive SOOO much better.

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95GT B303 cam, 1.7 rockers, 65mm TB, milled heads, 355's K&N, BBK Longtubes, Flowmaster cat back, pulleys, msd coil, 9mm wires, Tremec 3550, Pro5.0 shifter,10.5 Motorsport clutch, FMS aluminum driveshaft, weld in subframe connectors

On second thought the metalic part sounds strange. I never had any metalic sound. But check the U joints anyway, good luck.

I got a FMS AL driveshaft CHEAP CHEAP CHEAP !!! (lucky me !) so I'm going to put that in tomorrow, just gotta find the socket head that fits !! : )

Sorry, I forgot to add that the metallic sound (I think) is coming from the MAC shifter, the screw stops, its the shifter handle vibrating against that... but, we'll soon find out what is causing that serious vibration !

I'll post what happens w/ the driveshaft swap...

as for the main shaft, what could I do to check that? is that an auto-shop job??

thanks guys !!

actually, I just had a thought !!

I got the u-joints replaced when I got my car certified, along with the flywheel resurfaced (and machined)

back then, now if my memory serves me correctly, the car rode smoothly..

but, what if the flywheel was machined "wrong", and over time, pressure was being placed on the u-joints, and now they are failing prematurely? if I get this new driveshaft put in tomorrow, and its fine, should I reconsider getting a new flywheel? (since this one has been machined over 2 pounds lighter, is there enough material to work with?) because soon enough, the new u-joints will fail???

does this make sense? is it possible to machine a flywheel "wrong" (I have worked a lathe many times, and I've turned down material "cock-eyed", could a professional do the same?)

okay, will post what happens after driveshaft change..

Also, if its time to change the flywheel, is one better than the other, is lighter REALLY better? is Aluminum worth it? or just go with the stock Ford one for $95 bucks??

THANKS ! : )

It won't be driveshaft if it's RPM related. Mine does that too sometimes and I just assumed it to be something in the B&M shifter. Been doing it for over a year and nothing has failed. An incorrectly machined flywheel would cause the clutch to burn out faster but I don't think it would be vibration related.

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'91 LX Hatch, 17 ROH ZR6's, lowered, 3.73's, offroad H pipe, SN Cobra cat-back, ASP pullies, 14° timing, C&L 76mm MAF, 170A 3G, B&M Ripper on a T5
1991 LX Hatch 5.0L

OK, I think I was dealing with two seperate problems, not related.

1) my one problem is lurching off of idle, I think that is flywheel related, cracks in it could cause un-even clutch grabbing.

2) the vibrations are (pretty sure) driveshaft related.. going to install it l8r this afternoon, and will check back..

SO, lets goto problem #1) haha, if the flywheel is starting to crack, how much life does it have left to live?

i think that it is driveshaft related, cause he says it occurs in gears at certain rpms, and those rpms are progressively lower throughout the gears, indicating it is actually connected with speed, not rpm. driveshaft should do it.

When im around 90-100 mph, i feel a whoop whoop" noise, kinda like a pulsing vibration, and i have the aluminum d/s, it is worth the money though, and it kinda fixed the low rpm vibration i had.

That is very very bad and unsafe. The first time it happened to me it scared the $hit out of me. I was doing about 110-115 and immediately stopped racing. If your DS disconnects or fails at that speed....

Get it checked out.


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95GT B303 cam, 1.7 rockers, 65mm TB, milled heads, 355's K&N, BBK Longtubes, Flowmaster cat back, pulleys, msd coil, 9mm wires, Tremec 3550, Pro5.0 shifter,10.5 Motorsport clutch, FMS aluminum driveshaft, weld in subframe connectors

OK, got the new driveshaft in (boy its light!) AND its much much smoother, no vibrations, I hit 5000 rpm's in 3rd, and 4th gears... no vibration !!!

And, I don't know if others noticed this, but the shaft seems to echo the exhaust when driving, its strange, but it sounds cool ! : )

I am so impressed...

So, thanks a lot guys !!!

http://www.mustangworks.com/msgboard/biggrin.gif http://www.mustangworks.com/msgboard/biggrin.gif http://www.mustangworks.com/msgboard/biggrin.gif http://www.mustangworks.com/msgboard/biggrin.gif http://www.mustangworks.com/msgboard/biggrin.gif http://www.mustangworks.com/msgboard/biggrin.gif http://www.mustangworks.com/msgboard/biggrin.gif They ARE light arent they! I was throwing mine up in the air and catching it going "DAMN this thing dont weigh $HIT!"

Im glad you fixed the problem. I bet your whole car is waay smoother throughout the whole rpm band.

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95GT B303 cam, 1.7 rockers, 65mm TB, milled heads, 355's K&N, BBK Longtubes, Flowmaster cat back, pulleys, msd coil, 9mm wires, Tremec 3550, Pro5.0 shifter,10.5 Motorsport clutch, FMS aluminum driveshaft, weld in subframe connectors

fastang, yes, its light, and its smooth, it lauches "different" too !!

but its way smoother thru-out the range !!

thanks...