Clunk noise update
 

I had previously posted about a cluck noise when you tap the accelerator. A very metallic pink type clunk.

Since ive checked motor mounts and tranny mount. No obvious movement. Replaced both u joints also has drive shaft balanced. Replaced rear shocks.

Many things improved but the noise remains. It’s repeatable and easily heard.

Today I heard it without car moving. Hmm. I was previously convinced is was only in motion. Put on lift and with second set of ears seems to coming from flex plate torque converter area. Thoughts? I do have solid rear main seal leak.

Gez, could you be more vague?

What does that last sentence mean?

That you have a confirmed bad rear main leak?

What where you moving around when the car was on the lift and you heard the sound again?

Loosen the converter and slide it back into the trans. Crank it and see if you hear the noise. If you suspect a cracked flex plate or loose bolts, you can remover all the trans to engine bolts, install 2 long shouldered bolts on either side to slide the trans back enough to get a wrench on the flex plate bolts. I have skinny arms and used to replace cracked flex plates this way. Of course you’ll have to ensure the trans mount is loosened enough to slide. I have seen-heard knocks related to worn crankshaft thrust-bearing. That also tends to cause oil leaks at the rear seal also…. Just thoughts at random.

A member with 90 posts gives a friendly update, and makes a simple inquiry. Are you TRYING to chase newer people away, and put the last couple of nails into a dying hobby?:confused:

Really?
Why would you think that ( why don’t you let him speak for himself ) when I obviously want to help out if I can / could .

The "Gez, could you be more vague?" sounded very snarky.

Maybe my insight is off, tho.

I'm sure he can speak for himself, so carry on.

It did sound snarky. Just sayin. But I appreciate any advice.

The rear main seal leaks… just as fyi. In case that is useful? Wtf do I know.

The noise happens frequently when you tap the gas. Whether parked or driving. It is a very distinctive sound. I was honestly very surprised that the noise happens anytime as I expected it to be transmission, u joint, rear diff related.

I will see if I can get a look at the flex plate and spot anything out of the ordinary.

Thanks

In post #1, in that whole last paragraph you posted I need to ask for more detail.

So the car as described was / is on lift, but was the engine running ?

If it was running I have a disturbing possibility to lay out here.

I have seen this bad issue twice on SBC motors and one motor was only a low power 2 bbl motor.

Here’s what took place,.

A customer finally came in with the car after complaining about a noise and a new oil leak at the rear of the motor, he was complaining for two weeks over which time he put 150 or so miles on the car.

After 3 test drives and hearing this noise we had the car on a lift and running with a guy inside to go on and off the gas and also just at idle, but shifting ( auto trans ) from drive to reverse.

Nearly everytime we heard a noise like a clunk .

We narrower it down to coming from the bell housing area.
We then backed the converter off and found that the rear of the motors cast crank was cracked completely through, yet it was cracked in a way that it was still able to drive the converter.

It was cracked kinda like a jagged cog and a tooth

One of these motors was a 2 bbl 350 and the other a 4 bbl 400, both with cast cranks.

I hope this is not the issue with the OPs motor, but I am just putting it out there because it needs to checked and ruled out before the motor is ever started up again if possible.

Also one other possibility comes to mind since the OP confirms a bad oil leak back there,.

That possibility is that the rear main cap might be cracked which might be really hard to rule out or confirm with the motor assembled and in the car.

I hope just a cracked flexplate is found or the converter to flexplate bolts are loose, or a loose trans to engine bolt is found .

Good thoughts. It was running on the lift. I am fortunate enough to have one in the garage. Bell housing area seems to be the spot. The car is a 2bbl 350. All stock. Runs and drives nice but many things are tired. I’m making progress.

I’m going to take the cover off today and see if anything obvious shows up. My guess is I will need to take it in to see someone. Ideally the engine needs to be pulled so the rear main seal can be fixed and a good survey of the engine done. A full rebuild seems likely a some point but the car budget is basically shot for this year.

That’s a good plan, but please if you find it will need to go to a shop to get yanked and fixed because your own inspection found nothing do not drive it there .

Get it flatbeded to the shop, so your chance of loosing the whole motor will be greatly reduced.

As expected I found everything looked good under the flywheel cover. I did notice that one of the tranny crossmember bolts was stripped. Th350. Not the ones onto the tranny itself but one that goes from crossmember to bracket. Needs fixing but I checked and it isn’t the culprit. When rev and produce the noise nothing moved.

Have you done the unbolting the converter and seeing if the clunk is there still? (and sliding converter back away from flexplate)


:confused:


Probably time to pull tranny and engine.


:(

no I have not done that but it makes perfect sense. That would certainly isolate the noise to one side or the other.

Next question... and maybe new post is how easy will it be to separate the torque convertor from the flywheel with everything in the car? I assume it is a wrench on the tc side and a ratcheting wrench in the engine side?

Yes. Then rotate the flexplate to next bolt. will be three total. Sometimes the rotation may be kind of hard to turn. Possibly take plugs out for easier turning?


:)

Some people tap it around using the starter, but once I crawl under the car I don't like to crawl back out. So I take a large flat blade screwdriver or a smaller prybar, and advance the flex plate around by prying the teeth against the transmission housing until I get each bolt accessible. Once I have it accessible, I lock the flexplate in place with a pair of vice grips so the flexplate doesn't turn.