Expert: Rob Painter - 12/9/2011

Question
QUESTION: Perhaps 2 different situations:  about 1 time a week when i start the 92 deville i hear clunk. On one occasion it clunked 3 times. feels like in front and low. One time it would not go in gear from park to drive, i returned it to park and then in drive it engaged. Once it moved slightly forward in park. all this in the last month. i have a habit of turning the key off and then putting it in park. could the clutch plates be sticking.

ANSWER: Hello,

The clutch plates are`a separate entity from the parking pawl that engages when put into park. Now, it is almost impossible for me to diagnose a noise in the vehicle in which I cannot hear the noise. With that said and your explanation that you turn the ignition off before putting it in park makes me think that possibly you are putting pressure on the parking pawl and that would give you the same issues you are asking your question about.

The car should have no motion when put into park and you can literally over time break the mechanical pawl off. I have seen this a couple of times in my career.
Let's say you park on a steep hill. The car rolls ever so slightly before it is put into park. Pressure is now on the parking pawl. Now you start the engine and shift the transmission, you will hear a clunk because of he excess pressure on the pawl.

Pay attention when parking and put in park before turning the key off first and do this for a couple weeks and see if the noise is gone and get back to me.
There is more than just the linkage to the transmission. There is also a park cable that you could be stretching when putting the vehicle in park after the key is turned off and you are putting the shift lever in Park. This will not cause a clunk, but will cost you lots of money to replace when stretched out prematurely.

As for the one time that the trans was shifted to drive and car would move, no one can have an answer for this for one time, but could go back to the park cable I was referring to.

Have you checked the color of the trans fluid? You didn't state the year, make and model, so I don't know if you have a closed system in which you have no transmission dipstick. Checking is not for a clunk, but to see if the color is red or burned black which would have clutch pieces.

Generally a clunk sound is caused by something mechanical. Engine/transmission mounts, axle, parking pawl.

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---------- FOLLOW-UP ----------

QUESTION: thanks, it's a  92 caddy deville. 177, 800 miles .  i had mechanic check the trans fluid, no smell, good color. no hills here, florida car, quite level, so maybe no strain on the  pawl but now from me !! i will return to putting in park then turning off. i will let you know, thanks again.

ANSWER: Hello,

I just gave the hill scenario to make you understand that the problem might relate to the way you are parking the car, not necessarily because of hills. Intermittent problems are very difficult to find and they need to be narrowed own a to what may be causing them. I was thinking try putting it in park before turning the ignition off, because this is an anomaly you are aware of.
People commonly expect exact answers after an a sound or a rattle happens one or two times without a technician hearing it. Vehicle repair is not that simple. The problems require replication in which they can be narrowed down.
I have a girlfriend 1,500 miles away that has a noise on the right side of the car that no one can fix. The mechanic wants to charge her $600 to change the heater blower motor and I know from her description, that the blower is not the issue and I am leaning more to a axle problem. I have her trying to repeat the problem and paying attention to details. A heater blower is not going to make noise on on right turns.

I have been around in the repair industry I know the questions to ask even on the internet. I have been amazingly successful at diagnosing problems from thousands of miles away, however the problem needs to be repeated in which one knows by doing a certain thing, the event will happen again and again.

Let's say there is a clunk every time the vehicle is in drive and when accelerated. The first suggestion would be a engine or a transmission mount. Now, in a more specific situation, the clunk is only when you turn left. Then I would be looking at a CV joint in the axle.

Noises are not as simple as a no start problem in which there are specific simplistic issues to go to like diagnosing power to the starter. In that case, you either have power going to the starter or you don't and there are hard set diagnostics to find the problem.

In your case, we need to see if your method of turning off the car is the problem or something else. It may be something that is indicating a problem is developing, but has not gotten serious enough to show it's ugly face yet and will require much more driving before it can be repeated to the point the problem can be narrowed down. Some of these issues can be frustrating to diagnose.

Let's see what happens by parking the car differently than you normally do and then we go fromthere.

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---------- FOLLOW-UP ----------

QUESTION: hi again. Ok , got the idea you are steering me towards.  I have heard the clunk 2 times and it seems to be fainter than before. Previously the noise seemed to get getting worse. The two times i  have heard it since we talked  i had followed the instructions and put in park first before turning off. it was maybe 2 days after i started doing this, then the 3 rd day after following instructions. also did not mention i need motor mount in rear, and an exhaust donut.   beginning of this year i replaced the front mounts under the ac. just saying this cause you mentioned mounts. i also have a squeak,  it is the struts we think.. specially the left side is chirping like a bird all the drive long.

Answer
Hi,

Change the bad mount and see if the problem goes away. The exhaust donut problem just makes your car sound like a race car-lol.
The chirping can only be caused by the struts if the car is bouncing up and down the road and speed has nothing to do with the noise driving unless you are going down a bumpy road. The way we would check shocks, springs an struts is to put your knee on the bumper and bounce the car. If you hear the noise, it's in the suspension.

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