Drivetrain Excessive Vibration at 4K+ RPM while in gears - Any ideas why? 1993 Mustang GT 5.0 with T5

JCBeaver

Member
Mar 23, 2018
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Good evening StangNet,

I have a 93 Mustang GT that I finished up about 2 months ago. I am experiencing excessive vibration at 4K+ RPM making me not want to push the car. The motor spins freely and smoothly in neutral. But when in gears, it likes to vibrate A LOT at 4K making me not want to push it at all. It does not feel right. I did the clutch job twice over and I blamed my clutch job due to noticing good amount of clutch dust on my freshly painted T5 and I keep smelling burning clutch smell even after over 300 miles driven on this clutch.

I took it to an expert mechanic Wayne near Dulles airport in VA to confirm my thoughts. He actually confirmed that it vibrates way too much at 4K RPM and he was kind of scratching his head. He told me that he is not a fan of Poly motor mounts so he suggested that I change out to OEM replacement rubber mounts. Other than that he does not think my clutch is an issue. He guessed that it could be my clutch shaft pilot bearing that is going bad causing excessive vibration at high RPM considering that was the only thing I did not replace. Once again, he said it is just a guess.

Trying to see if anyone else got any ideas on what could be causing vibration at higher RPMs? Note that the fox shifts through gears no problem and it actually runs well up towards 4K RPM. I am facing a dilemma on whether or not should I have someone re do my clutch once again and spend the money even though it is just a guess that my pilot bearing is bad.

Thanks in advance!
 
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Mustang5L5

This is a big reason why I pulled it out
Mod Dude
Feb 18, 2001
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Is it 4K RPM no matter what gear?

If so, i would rule out trans. It would need to be in the flywheel/clutch/input shaft area if the RPM you get vibration at under load is always the same.

What parts are you using?
 
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JCBeaver

Member
Mar 23, 2018
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San Diego, CA
Yeah it will always happen at 4K. Moves smoothly up until I hit near 4K it will shake hard.. Also if I push it hard like doing a burn out or trying to have some fun on the road it shakes badly when approaching 4K or trying to punch into 4K RPM so I dont feel good doing it.

I am still scratching my head on this one. My trans, DS, and rear end was perfectly smooth before I pulled the drivetrain and did not touch those stuff, but I know anything can happen.

Expert mechanic, Wayne, thinks that it might be the pilot bearing, but I don't think so because the symptoms are constant.. not random vibrations like a failed bearing would give me?

Working against the clock as I am shipping the car to CA on May 5th. More than likely I will have to put this to rest, at least it moves fine under 4K so I will just get it shipped to CA and try to figure this part out over there. I am currently dealing with a possible electrical gremlin- intermittent starting/extended crank starts when everything was perfectly in order 1-2 weeks ago. Story of my life haha

Thanks,
-Jarvis
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
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Most of the time a pilot bearing will cause clutch chatter.
side note: the wrong firing order will give you a violent shake but usually at anything above an idle but I would check just to be sure.
 

Mustang5L5

This is a big reason why I pulled it out
Mod Dude
Feb 18, 2001
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Massachusetts
Firing on all 8 cyl?

Reason I ask is because I had a slight vibration at 3K RPM on my car. I had just done the 5-spd swap and chalked it up to something on the flywheel/clutch out of balance. Drove this way for a year....

Then I happened to be pulling codes and doing a cylinder balance test and discovered one cylinder was dead. I had been driving on 7 for a year and didn't know it. Car idles fine, revved fine, would leave rubber...but I just had that 3K+ vibration.

Fixed the dead injector and problem solved. I honestly thought it was flywheel/clutch related.
 
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CarMichael Angelo

Nobody appreciates me..I'm gonna cut my ear off
SN Certified Technician
Nov 29, 1999
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Good evening StangNet,

I have a 93 Mustang GT that I finished up about 2 months ago. I am experiencing excessive vibration at 4K+ RPM making me not want to push the car. The motor spins freely and smoothly in neutral. But when in gears, it likes to vibrate A LOT at 4K making me not want to push it at all. It does not feel right. I did the clutch job twice over and I blamed my clutch job due to noticing good amount of clutch dust on my freshly painted T5 and I keep smelling burning clutch smell even after over 300 miles driven on this clutch.

I took it to an expert mechanic Wayne near Dulles airport in VA to confirm my thoughts. He actually confirmed that it vibrates way too much at 4K RPM and he was kind of scratching his head. He told me that he is not a fan of Poly motor mounts so he suggested that I change out to OEM replacement rubber mounts. Other than that he does not think my clutch is an issue. He guessed that it could be my clutch shaft pilot bearing that is going bad causing excessive vibration at high RPM considering that was the only thing I did not replace. Once again, he said it is just a guess.

Trying to see if anyone else got any ideas on what could be causing vibration at higher RPMs? Note that the fox shifts through gears no problem and it actually runs well up towards 4K RPM. I am facing a dilemma on whether or not should I have someone re do my clutch once again and spend the money even though it is just a guess that my pilot bearing is bad.

Thanks in advance!
Did you change the freakin flywheel? Did you make sure it was matched to a 50 oz imbalanced rotating assy?
 

2000xp8

SN Certified Technician
Aug 8, 2003
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Just to be clear, it will or won't do this in neutral or with the clutch pushed in while sitting?