Noise & Vibration out of T5 in low speed/high torque situations

Chythar · Nov 29, 2010

Not sure if I can describe this right. My Cobra clone has had this issue for a while, not sure if it's always been there since I did the Cobra conversion. I can reliably repeat the issue when in 2nd (or higher) gear and low RPM's, usually around 1K or so. I hit that point going up the parking garage at work every time I turn a corner. No issues exiting the parking structure, but the rpm's are definitely higher then. The vibration and loud noise can be felt throughout the car and lasts for a bit until the rpm's climb enough. The noise sounds like something is loose and rattling around. I haven't noticed any slipping of the clutch, nor any noticeable effect to car performance other than the noise and vibration. The rattle sounds like it's coming from right under the center console, near the shifter.

I do not feel any vibration at any other time. No problems shifting gears, no problems with any vibrations or noise in any gear other than this issue. I checked for anything loose under the car this weekend, but I couldn't find anything. The vibration does not occur if I am in neutral. Haven't tried to push in the clutch when the vibration happens, I'll try that tomorrow.

For a bit of comparison, I've noticed a similar vibration in my 95 GT. In any gear around 1K rpm, I can feel a bit of a vibration and a change in exhaust tone, kinda like the engine is bogging down a bit. No rattling noise, however. To me, the GT is exhibiting the same type of basic behavior as the Cobra clone, but the Cobra's vibrations are much bigger and the rattle is quite loud.

I got all the Cobra parts from a wrecked 95 Cobra with a bent frame, so it's entirely possible that something is broken. But I can't find out what.

I have a FMS aluminum driveshaft on the Cobra clone - could this be a loose u-joint? If so, wouldn't I be getting vibrations at higher rpm's? Any ideas would be appreciated.

Chythar · Nov 30, 2010

Lot of lookers and no comments. This can't be that original of an issue, folks. Tested a bit this morning, the vibration dies out pretty quick when I push in the clutch. I can feel some vibration through the shifter handle, but about as much as I feel through the seat. The handle doesn't shake at all. Oh, I can hear the vibration when going from neutral to 1st if the rpm's are low when the clutch fully engages. If rpm's are 1200 or higher once the clutch fully engages, no vibration.

Any chance this could be a clutch problem? This is the clutch that was on the Cobra when I converted things over, with a little over 50K on the driveline. Likely it's the original OEM clutch.

seijirou · Dec 1, 2010

That's a tough one without hearing it or feeling it yourself honestly. I don't think you're going to get much more than some guesses on the board.

I will say that it doesn't sound like anything driveshaft, clutch, or flywheel related.

It may be that you're getting some pinging if you're borderline lugging the engine. If you're not running higher octane now, try a tankful next time and see if it goes away.

The only other things that come to mind would be the motor and/or transmission mounts. If they're worn, in the circumstance you're describing, you may be flexing them and causing some buzzing somewhere. Also take a look at the smog pump tube that goes to your H or X pipe and see if it's snuggling up to your transmission or something.

Chythar · Dec 1, 2010

Can't go any higher on octane, Cobra engine requires premium fuel already. Can't hurt to toss in some octane booster just in case. Motor and tranny mounts were new a year ago, Energy Suspension poly mounts. I do feel more vibrations for the car all around with the poly mounts, but nothing like this.

Already checked the smog pipe, it isn't loose and isn't touching anything. I'll be under the car this weekend, so I'll take a closer look just to be sure.

Thanks for the input. Any guesses are very appreciated, 'cause I have NO idea what's going on.

fordtech28 · Dec 2, 2010

if you have the poly mount for the transmissions theres your problem since our crossmember doesnt have rubber bushings the stiffer mount makes the vibrartions go through the chassis

revhead347 · Dec 2, 2010

fordtech28 said:
if you have the poly mount for the transmissions theres your problem since our crossmember doesnt have rubber bushings the stiffer mount makes the vibrartions go through the chassis

Good to know. I've had noise issues with 5 speeds before, and always with a poly mount.

Kurt

Chythar · Dec 2, 2010

fordtech28 said:
if you have the poly mount for the transmissions theres your problem since our crossmember doesnt have rubber bushings the stiffer mount makes the vibrartions go through the chassis

I know the poly mounts transfer more vibrations, but this kind? I admit I'm a bit hesitant to just blame it on the poly mount. However, I can test it - I have a tranny poly mount for my GT that I haven't had time to install. If the noise appears on the GT after the poly mount goes on, I have my answer.

Would be nice if it was that easy of a fix.

fordtech28 · Dec 3, 2010

Chythar said:
I know the poly mounts transfer more vibrations, but this kind? I admit I'm a bit hesitant to just blame it on the poly mount. However, I can test it - I have a tranny poly mount for my GT that I haven't had time to install. If the noise appears on the GT after the poly mount goes on, I have my answer.

Would be nice if it was that easy of a fix.

the poly mount might be part of the issue if it reduces the vibration you might have a problem with either the clutch or the transmission my cousin has a 90 fox body and we had a very similiar issue for him it ended being the flywheel even though it was brand new

m0l0 · Dec 3, 2010

if it is the original clutch , could be the pilot bearing along with the clutch, otherwise as they comment the poly mounts

Zero_chance · Dec 12, 2010

Just out of curiosity, was the car in question previously an auto that you swapped a five speed into? I had a similar type issue in my 95 after doing the five speed swap, turned out the tranny was hitting around where I had trimmed the opening for the shifter. Only did it under certain RPMs as well, usually when I was chugging along and turning as the vibrations combined with the flexing made it hit.

Chythar · Dec 13, 2010

Zero_chance said:
Just out of curiosity, was the car in question previously an auto that you swapped a five speed into? I had a similar type issue in my 95 after doing the five speed swap, turned out the tranny was hitting around where I had trimmed the opening for the shifter. Only did it under certain RPMs as well, usually when I was chugging along and turning as the vibrations combined with the flexing made it hit.

Why yes, this car was previously an auto. That's a very good idea, perhaps I didn't cut a big enough opening for the shifter. I'll check that out.

Zero_chance · Dec 13, 2010

Figured I'd throw that out there. That's where my issues came from and they sounded similar. I had contact on the front part of the shifter base going toward the engine. Required a little more trimming and some prying but I made enough clearance and the noise is gone. Just something to double check.

Chythar · Jan 9, 2011

Finally got a chance to poke around under the car. Nothing is touching around the shifter, but one part was pretty darn close. After prying at the metal and making some room, I decided to try something and see if I could learn anything new: I pulled off the shifter bezel and the rubber insulator to expose the tranny, then took the car for a test drive. Sadly, the sound is still there and has not changed.

I can recreate the sound if I'm in 2nd and below 1K rpm. When the rattle is there, the tranny barely moves at all at that slow speed, and it doesn't touch the metal around the shifter. Could not feel any vibrations anywhere in the sheet metal around the shifter, but I could feel small vibrations when I touched the tranny itself. Sounds like the problem is in the driveline or some other part of the driveline is touching the tranny.

The search for the mystery rattle continues....

Zero_chance · Jan 16, 2011

Any update on the noise issue?

Chythar · Jan 18, 2011

No updates, I'm not really sure exactly where else to look. I guess I simply need to keep looking for something loose on the chassis.

divit250r · Jan 19, 2011

Are you sure it's not just from lugging the engine? Every stick shift I've driven would create some pretty harsh shudder / groan / rattle sounds if you lugged it. I know my car does, and that's with 3.73s too.

Mintsick · Jan 19, 2011

divit250r said:
Are you sure it's not just from lugging the engine? Every stick shift I've driven would create some pretty harsh shudder / groan / rattle sounds if you lugged it. I know my car does, and that's with 3.73s too.

This, almost every vehicle I have owned in the last 13 years has been a manual and if I lugged the motor in 2nd/3rd gear where the rpms were 1k or under I'd get a shudder/rattle sound like you are describing. I can easily do it in my fox with the 2.73's.

Chythar · Jan 19, 2011

Agreed on the shudder, I get it on my 95GT as well. The Cobra has that shudder, and I did expect that at low speeds. But there's an additional rattle that sounds like two pieces of metal bouncing against each other that I'm trying to track down. I really should just get some video with the rattle in it for folks to hear.

divit250r · Jan 21, 2011

Chythar said:
Agreed on the shudder, I get it on my 95GT as well. The Cobra has that shudder, and I did expect that at low speeds. But there's an additional rattle that sounds like two pieces of metal bouncing against each other that I'm trying to track down. I really should just get some video with the rattle in it for folks to hear.

What about the heat shields on the cats? Assuming it doesn't have an O/R pipe on it.

Scott

Chythar · Jan 22, 2011

The Cobra clone has the original h-pipe on it, so yes it has cats. I tapped each one by hand and nothing seemed loose, but I imagine a cracked weld wouldn't show up too easily. The donor Cobra was in a wreck that bent the frame, so it's entirely possible one of the heat shields are loose. Any way to check for a loose weld? Or do I need to rent a welder and make sure they're all welded all up tight?

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