Vibrations, Vibrations, Vibrations....

[red95gts]

Sometimes a good thing, but in this case, definitely a bad thing...:)

Lemme make sure I have all my bases covered here...

The vibe starts at roughly 4700 rpm and as rpms increase, so does the intensity of the vibe. By 5500ish, the shifter is making a rattling noise and it's vibrating like crazy.

I have replaced the balancer with a stock rebuild from O'Reilly's. I have replaced the clutch with a factory-spec Zoom unit. While the tranny was out, I checked the endplay and inspected the input shaft. Also replaced the pilot bearing while I was in there.

And it still vibrates.

Just this weekend, I put some GT-40 valve springs on the car since I figured maybe I was floating the valves with the stockers and that was causing the vibe....long shot for sure and as I figured..it didn't do a damn thing but eliminate the springs as a culprit..:)

So, I'm looking at a couple things now...

Flywheel: Could it be slightly off-balance? Maybe I just don't feel the vibe unil 4700rpm, but it's actually there at any rpm?

Balancer: Same thing as above...maybe it's off ever so slightly. The vibe has been there since I bought the car and persisted even after I swapped balancers....so I'm doubting this one.

Motor/Tranny mounts: Anyone have one of these go bad and cause a vibe? Can you describe the vibe? (i.e. how severe, what rpms, etc, etc)

Misfire at high rpms: I've replaced the coil for other reasons, and the cap and rotor look worse for wear, although the vibe was there when the cap was new....so I dunno

Am I missing something here?? LOL

[Neighbors]

Darrell,

I did have a tranny mount go bad on my Mustang in college. With a C4 and 3.00 gears, the vibe came on strong about 70MPH. I rebalanced the tires a couple of times thinking that might be it, then discovered the tranny mount had failed in shear...

The vibes stayed with me w/speed, and I can't remember what they did after hitting 70 and beyond; did they get worse?

When you free rev the engine, does it vibrate? How was/is your pilot bearing? Gear set-up fine (any play in pinion)?

/me is thinking out loud...

Nay!

[red95gts]

Hey Chris! Thanks for the response.

The vibe is defintely rpm-related as oppssed to speed as it occurs in any gear at the same rpm.

When I goose the engine pretty hard in neutral I can feel the vibe around 3000rpm or so...

The pilot bearing is brand-new as of the day after Xmas...

I did notice some play in the pinion when I pulled the axles out a while ago. Although, with it being a rpm-related vibration...I dunno if that's the problem or not. That will definitely get taken care of when the 4.10s go in the car.


Thanks again Chris

[Shaggy]

My guess is the flywheel with all the outher parts you have replaced...Or because of manufacturing tolerances the whole rotating assembly is out just a nth (yes scientific term nth :) )

[TTop GT]

i know exactly the rattling sound that you get through the shifter... mines does it too in 3rd and 4th from about 4200 to 5200 rpm (its kind of a hollow knock or tapping sound but really fast)sounds like something inside the shifter handle is rattling around... too bad its solid i know its not faulty motor or trans mounts cause mine are solid aluminum:D ive got no idea what it is i just kinda took it as a sign to start saving for a new trans. i figured it was nicely telling me it was going to come apart:(

[TTop GT]

the vibration really stumps me...

i have solid mounts, fresh king cobra clutch, mew FRPP billet steel flywheel, and FRPP alum d-shaft, on a T-5z that i got from summit, and it was all installed at the same time

i really have no idea what it could be, when you find out please tell me:) -damn...even got it to rhyme

[red95gts]

Thanks for the ideas guys! My fear all along has been a factory mis-balance. Fortunately, I have a spare block, crank , rods, and pistons should I need to just build a new short block.

The tranny needs a rebuild and I'm undecided as whether or not to throw a new flywheel in the car. If I do, and it fixes it....I'm set (this motor leaked down 6-8%)

If it doesn't fix it....the flywheel I'll need to balance the new short block is installed on the car...haha

Oh well..I guess I'll sleep on it

:)

Thanks again guys!

[Blue91]

Originally posted by TTop GT
i know its not faulty motor or trans mounts cause mine are solid aluminum:D


Are you saying BOTH your trans mount and your motor mounts are solids? If so, you need to change that. There is a greater chance of breakage using solids in both locations. I'd put a stock rubber trans mount on and leave the solid motor mounts.

[TTop GT]

yea... its all solid

i was told the exact opposite... that it must all be solid, or all rubber:hmm: :( never both cause it could bind or cause problems