Gearbox Mount - No Good If It's Not Torn

[Birth]

Hi there, I am getting a major clunk under my car - it feels like it's coming from the driver's side firewall or around the gearbox tunnel. I have changed the engine mounts and the power steering rack bushes. Pedders tell me that it is a ball joint on the drivers side; though I am thinking that it is probably a gearbox mount. I have had a mechanic look at the gearbox mount who reckons mine is ok; can the gearbox mount be rooted if it isn't split etc? Thanks, Ben.

[Birds]

Not really, usually you see some sort of physical damage before it begins to affect things. However, age can certainly make mounts decrepid which isn't as obvious as cracking/splitting. This said, I don't think a damaged gearbox mount would cause this sound...they usually only result in excessive vibration.

When is this happening, when accelerating? Just cruising along in gear? Turning? All the time? In certain gears? Coasting in neutral? etc.

[Birth]

Thanks Birds; I am not getting any vibration at all and the gears etc. are changing well (in fact my car feels better than it has in years except for this clunk!)

When I turn the car on I get a clunk sound from down near my left foot

When I drive the car and it begins to move forward I get a heavier clunk

When moving, if I accelerate heavily I get a clunk

When moving quickly, if I brake heavily I get a clunk. The clunk doesn't seem related to braking, rather, a shift in the weight in the car

When stationary, if I push down on the guards there is no sound

When stationary, if I push the car backward and forward I get no sound

There is no sound when I rev the engine in neutral

Under the car everything seems tight - no bushes etc. seem torn or missing (though several are old / worn)

Under the car nothing seems to be fouling, i.e. there are no rub marks

The engine mounts are standard Nissan items. I installed the, they are in flush and all of the bolts are done up tightly

[Birds]

I do apologise...have just checked with one of the mechanics at work, and based on your symptoms listed there he would put his money on a gearbox or engine mount. Apparently they can appear to be normal and then move around when the car is in motion. I agree with him

Edited June 30, 2009 by Birds

[salival]

Thanks Birds; I am not getting any vibration at all and the gears etc. are changing well (in fact my car feels better than it has in years except for this clunk!)

When I turn the car on I get a clunk sound from down near my left foot

When I drive the car and it begins to move forward I get a heavier clunk

When moving, if I accelerate heavily I get a clunk

When moving quickly, if I brake heavily I get a clunk. The clunk doesn't seem related to braking, rather, a shift in the weight in the car

When stationary, if I push down on the guards there is no sound

When stationary, if I push the car backward and forward I get no sound

There is no sound when I rev the engine in neutral

Under the car everything seems tight - no bushes etc. seem torn or missing (though several are old / worn)

Under the car nothing seems to be fouling, i.e. there are no rub marks

The engine mounts are standard Nissan items. I installed the, they are in flush and all of the bolts are done up tightly

Starter motor loose maybe?

[Birth]

Thanks salival; I really thought you had it - but I got under there tonight and the starter motor looks fine. I did notice that the front sub-frame mounts were a little loose - I tightened them right up by it didn't help.

I did notice tonight that the bushes on the top of the gearbox mount bracket are missing - I am sure that it is a contributer - though I will need to see if it fixes the problem or if it was just another thing to get on top of - thanks for the thought though!

[GTRsean]

A loose gbox x member can make a clunk noise. I had to repair my mount holes (threads were stripped making a couple of the bolts loose and clunked as well) with helicoils as the gbox has been in and out many times in the cars life!!

[Birth]

Did you have to get new bushes - did you get Nissan or another brand - where?

[Birth]

I got Nissan bushes. The part number is 11248-85E01. These cost $20.48 plus GST each. Do you know if the tapered end faces down towards the ground or upward? Thanks.

[Birth]

I put the new bushes into the gearbox cross member and the probelm is fixed! I did notice that two (of the four) holes where not letting the bolts tighten right up so I assume that I have the same problem that you had GTRsean. I see that you used helicoils to repair the holes. I've never used these before and have found that there aren't any threads which really deal with the process - are you able to explain how it works?