Please help diagnose mystery noise...

[hoggy]

Allegro: I had a 93 Trans Am. What you are hearing in your Trans Am and Corvette is the lifters and not piston slap. They are roller lifters and when they get a bit loose (if that's thre right word) they start to make noise if the oil drains out over night. Once the lifters pump back up with oil the noise goes away. As far as the Toyota noise I doubt that is lifters as they run on a shim between the lifter and cam like some of the Japan bikes do such as the old Z1 900, but may be true piston slap although I'm not convinced it is. But it is really hard to tell from the video and others seem to know more about it than I do. Also I don't think actual piston slap goes away when warm or under load. It usually sounds louder.

 

[hoggy]

Listened to your video a couple more times and I think what you have is a cracked flex plate. Better have your mechanic check it out. Let us know what it turns out to be.

 

[KP Texan]

Allegro: I had a 93 Trans Am. What you are hearing in your Trans Am and Corvette is the lifters and not piston slap. They are roller lifters and when they get a bit loose (if that's thre right word) they start to make noise if the oil drains out over night. Once the lifters pump back up with oil the noise goes away. As far as the Toyota noise I doubt that is lifters as they run on a shim between the lifter and cam like some of the Japan bikes do such as the old Z1 900, but may be true piston slap although I'm not convinced it is. But it is really hard to tell from the video and others seem to know more about it than I do. Also I don't think actual piston slap goes away when warm or under load. It usually sounds louder.

The '97+ LSx engines were pretty well known for having cold piston slap. On the contrary, my '96 LT4 never had piston slap and I don't really recall hearing about any LTx engines that had the issue.

-Wes

 

[bluduk15]

Listened to your video a couple more times and I think what you have is a cracked flex plate. Better have your mechanic check it out. Let us know what it turns out to be.

I took off the access plate and was able to inspect most of the flex or drive plate by marking the viewable area then starting the car and moving it a bit.

I didn't see any cracking on the areas that I could inspect, but I didn't get to all of them.

HOWEVER, I swear that I could hear THE noise very faintly coming from the drive/flex plate.

Any futher ideas for more troubleshooting?

 

[hoggy]

Without being there to hear it up close I cannot think of anything that has not been suggested. If you have a stethascope (spelling) most of us don't, you might be able to hear better. Or take a large screw driver and put the handle to you ear and touch the point to the area where it sounds like the noise is coming you may be better able to pinpoint what it is. A good transmission place should be able to tell you if it's the flex plate easy enough.

 

[KB084RUNNER]

Another possibility is the torque converter in the transmission. This could explain why it goes away when warm. If the TC is going bad it could make noise until fluid fills it. Have you checked your transmission fluid level or ever serviced the trans?

Since the entire converter (pump, turbine and stator) turns while the transmission is in park and neutral, a converter noise will go away in those ranges. When the transmission is in gear and the drive wheels are stationary, the turbine in the torque converter doesn't spin, because the turbine shaft is stationary. This is when the bearing between the turbine and main housing of the converter is working. If the noise is there only in gear with the drive wheels stationary and goes away in neutral, suspect the torque converter.

If the flex plate is bolted to the TC then those bolts can come loose and should be checked for tightness as well.

 

[bluduk15]

Another possibility is the torque converter in the transmission. This could explain why it goes away when warm. If the TC is going bad it could make noise until fluid fills it. Have you checked your transmission fluid level or ever serviced the trans?

Since the entire converter (pump, turbine and stator) turns while the transmission is in park and neutral, a converter noise will go away in those ranges. When the transmission is in gear and the drive wheels are stationary, the turbine in the torque converter doesn't spin, because the turbine shaft is stationary. This is when the bearing between the turbine and main housing of the converter is working. If the noise is there only in gear with the drive wheels stationary and goes away in neutral, suspect the torque converter.

If the flex plate is bolted to the TC then those bolts can come loose and should be checked for tightness as well.

Thanks for the analysis. This problem is hard to diagnose because of the variations of the noise, which are mostly dependent on temperature--outside air temperature and engine temperature.

Like I said, it's most noticeable on colder (sub 40 deg.) mornings. In these conditions, when I start the engine I don't hear the noise, but as soon as I put it in gear I do. If it's warmer, I might not hear the noise until I accelerate down the street. Just to complicate it even more, sometimes I hear it after I driven to work, parked and start to pull out of the garage (noise echoes off the walls).

Overall, the noise seems to disappear or is not very noticeable in a few minutes. The next thing on my list is to use an engine type stethescope to try to pinpoint the location.

 

[Noahfn]

I noticed the exact same noise in my 2006 V8. It only happens when I put it in gear and stops after driving just a short distance.

Have you found a cause/solution?

ETA: Sorry, I didn't realize this post thread was so old.

 

[bluduk15]

I noticed the exact same noise in my 2006 V8. It only happens when I put it in gear and stops after driving just a short distance.

Have you found a cause/solution?

ETA: Sorry, I didn't realize this post thread was so old.

I didn't find a true cause. BUT, soon after the thread I changed my oil and the problem went away. The oil was Royal Purple (always used it) and it was dirty (I drive in dusty environs) and probably a 1/2 qt. low.

The problem had never returned and I attributed it to dirty oil/low oil and cold weather. This is the only thing I came up with. Maybe it has to do with the oil drainback on the filter and caused some kind of valve chatter before the oil could be warmed and circulated well enough in a "somewhat" low oil situation.

So, good news, no real engine/valve damage and it might be remedied with a good oil/filter change. Bad news--don't have a definitive answer to the problem.

Update here if it works for you!!!

 

[Noahfn]

I didn't find a true cause. BUT, soon after the thread I changed my oil and the problem went away. The oil was Royal Purple (always used it) and it was dirty (I drive in dusty environs) and probably a 1/2 qt. low.

The problem had never returned and I attributed it to dirty oil/low oil and cold weather. This is the only thing I came up with. Maybe it has to do with the oil drainback on the filter and caused some kind of valve chatter before the oil could be warmed and circulated well enough in a "somewhat" low oil situation.

So, good news, no real engine/valve damage and it might be remedied with a good oil/filter change. Bad news--don't have a definitive answer to the problem.

Update here if it works for you!!!

I'm sure I have plenty of oil and the oil isn't dirty. I just changed the oil. I used Mobil 1, 5w30 and a Mobil 1 filter. Now that you mention it though, I don't remember it making this sound before the oil change, so maybe it is related to the filter. I have some factory filters in the garage, maybe I'll switch that this weekend and see if it helps.

 

[TONEDOG513]

I have the same thing since day 1.

very annoying and don't really believe that there is nothing to worry about. There has to be some wear associated with that knocking.

I hate it. Its actually kind of embarassing when other people say "hey whats that knocking"

my fords never did that... now that im thinking of it, I sold my last ford to my brother who now has over 300k on it and it sounds better than my '07..

oh yeah, his seat doesnt creak and pop either, come to think of it my old mans '90 grand marquis 5.0 with 428k on doesnt knock or have seat noises!

srry just venting!

T