i have had a new sports car for a little over a week.  it has a
standard transmission.  i let a friend drive it last night who i
mistakenly believed knew how to use a stickshift.  in fact, i was
somehow so confident in my friend's ability to drive the car, when my
friend started revving the engine while driving, i assumed it was just
showboating.
moments later, a horrible burning smell filled the air.  i told my
friend to pull over.  my friend shrugged off the incident as a "heavy
clutch" perhaps to save face.  this burning smell was present for
another hour.  later that night and today, i've noticed a new
behavior.  in both cases, after driving the car for more than a half
hour continuously, the car tends to vibrate when between 2nd and 4th
gears.  how likely is it that these two events are related or am i
just being paranoid because of the new car?  should i take the car
directly to a repair shop before i drive it any more?

Hi, whitney,

Some questions:

Was the vibration you've described there before your friend drove the
vehicle?

Is your vehicle under a warranty? You say it's a new car, but do you
mean brand new or new to you -- usually even a used car (from a lot -
not a private deal) has a 30 day warranty.

What make, model and year is this vehicle?

When do you get this vibration -- we understand the gears in question
-- but, does it also occur when you are just sitting still and rev the
engine or only when you let the clutch out and accelerate?

My husband, a mechanic of many years, has this opinion: There is a
good chance your clutch has been over-heated to the point that the
clutch disc and/or pressure plate has been damaged, resulting in the
vibrations you've been experiencing.

Riding the clutch and revving the motor would result in the burning
smell you've reported.

We suggest you take it back to the place from which you purchased the
vehicle. There is no guarantee that the (if you have one) warranty
will cover this situation. Your conscience will dictate whether or not
you report your 'friend's' participation in the situation.

Best advice:  Don't let your hot-dog friends drive your vehicles.

I've asked some questions which you should feel free to answer for
purposes of clarification. You don't know me from Adam, so I'll
understand that you might want to check further into this, but I'm
here to tell you that if my husband says your clutch is wrecked, it's
well and truly wrecked. Take the car back from whence it came.

I wish you well,
revbrenda1dst

"...car tends to vibrate when between 2nd and 4th gears."

You may not have noticed it but it is possible that you were not
driving on a smooth road.

i considered that possibility in both cases as i would prefer that to
be the explanation.  i guess i should be more descriptive than
"vibrate".  it wasn't the kind of vibration i would associate with a
bad road.  in both cases, there was the same distinct ominous
low-pitched noise that just didn't seem correlated to the road
condition.

another piece of info is that today it was evident that the
vibration/noise would go away when i put it into 5th gear.  this
appeared to be consistently reproducible.  the previous night, the new
undesirable behavior happened in a neighborhood so i never saw what
would happen if it went into 5th.

You may find that the vibration occurs when the engine is going at a
certain speed.  A "sports car" should have a tachometer - calibrated
in rpm.  See if the vibration occurs in the same rpm band irrespective
of gear.  You may pass through this band very quickly while
accelerating in low gears, but may spend more time in it in higher
gears, and may even sit in it all the time while cruising.  If you
have such a resonance, it is unlikely to be the clutch.  It may be a
vibrating belt or some other fitting or engine component.  If the car
is under earranty, especially if it is new, this is something that
should be fixed.  It could be in the exhaust system - stainless steel
exhausts are renowned for such buzzing.

Could also be a wheel alignment problem if it is particular road speed
that brings it on.  In this case, it will be felt through the steering
wheel more than heard.

Hope this helps a bit.

thanks for the feedback but this doesn't sound similar to the symptom
i was having as the noise/vibration was continuous through several
gears until i put it in 5th and then it went away.

I once had a similar problem with my 1968 Volkswagen Beetle. In my
case, replacing the steering damper solved the problem.

Bring it in.

jbf777-ga

The smell would have been something akin to burnt sugar ,if you know
what that is like. It was probably caused by your mate "riding"the
clutch while still revving the engine to prevent stalling. The lower
gears are harder to enage properly with a  burnt clutch as the grip 
is no longer there  to a sufficient degree having been sheared off by
your mate; ah buddy? pal? I mean.The grip is often made from asbestos,
in Australia at least. The grip required is not as great in top gear
if car is running on the flat or not being laboured so therefore your
experience of no problem in 5th gear. Vibration does quite sound like
what I would have called the problem faced in second gear witha burnt
clutch however.

 Good Luck.

  P.S Replacing clutch is a simple matter of intermediate cost

There is a simple test for a slipping clutch.  Engage the hand-brake
(aka parking brake).  Put the car in first gear, and try to drive off,
slowly releasing the clutch as usual.  If, no matter how gentle you
are, the engine stalls, the clutch is fine.  You can also try it in
reverse, but this is usually a very strong gear, and you may be able
to move a bit.  Bear in mind that this test makes two parts of the car
work against each other, so should not be done too frequently.

BTW, do you belong to - or have access to some car club or road-side
assistance service?  It could be worth a visit from them.
I'm a bit concerned that there may be a gear-box flaw - perhaps in one
of the cogs that is common to 3rd and 4th, but no other gear.  I'm
certainly not an expert in these things though.

Sounds like a possible cracked pressure plate.  Engine speed and
drive-line speed will affect the vibration.  Excessive "riding the
clutch" will cause the pressure plate to generate excessive heat
causing small fractures to occur when it cools.  I race and see this
problem on occasion.  Get your car to a good mechanic and have this
checked out.  Pressure plate failures are very bad things.