Good day oldsmobile family. For the past few days ive been searching the forum for this exact issue but i cant find it so forgive me for making another post on this . I have a Knocking sound that goes away when I put it in any gear . But comes back in park/neutral and rises as I give it gas . Now I have yet to actually take it down the road but I have put it in gear and drove down my driveway and back and it goes away till I put it in park . It's an olds 455 stock overhaul with new cam and lifters only . Maybe a total of 45 to 50 running minutes on the rebuild . When I start it it's real faint then gets a little louder but goes away in gear . Is it something serious? I have done the whole rebuild myself , im no pro by along shot but know my way around a engine . Any suggestions are great fully welcomed.

 

Knocking in park/neutral is an oddball. You can have a buddy start the car while you watch the engine. Bad motor mounts would cause the engine to rock when started. Also, bad U-joints can knock when shifting into gear, but...

 

? . I'm saying when I start the engine there is a Knocking sound like a rod knock but when I put it in gear the sound goes away nothing todo bout engine rocking or ujoint . ?

 

Check the flex plate and converter. Make sure they are tight.

 

X2 on the flex plate.

 

If you here the knock when turning the engine off on its last few movements it is very likely flexplate/converter related. Try starting the engine, opening the drivers door and listening while turning it off.

 

Ok it's like not loud but it is loud , I couldn't really tell with the engine on turn off method . But I ran across this before dropping body back on the frame , unbolted torque converter it stop so unbolted trans to look at the flexplate and check torque on the bolts and all was well I thought . I seen no crack on flexplate and bolts were torqued . Now could it had been like a hair line crack ? I mean my flexplate is the original from 73 so I seen like stress lines ( for a lack of better words ) but they didn't look like cracks . It did/does wobble while running I think I'm going to just bite the bullet and buy a new flexplate . But the main gist to this was to see if this was a sign of thrust bearing , and since it stopped when I put it in gear make sure no other issue does that such as any bearings or rods . Flexplate back I'm cool with that being the issue I just didn't want to have a fresh overhaul completely screwed. So long question shorten it does stop completely when I unbolt torque converter and with torque converter olted up only knocks until I put it in gear and it stops . So would any bearings or rod knock stop once I put it in gear ?

 

It's not the bearings!

 

So would any bearings or rod knock stop once I put it in gear ? Probably not stop, rather change.

If your certain it isn't the exhaust hitting something or something that shifts just enough when it's put in gear then examine the flex plate. Can the noise be heard most from inside the bell area? Use a heater hose next to your ear to determine the direction of the noise source. Don't let the free end of the hose hit anything rotating, it wiil make a severe noise in your ear...been there!

 

The car is running, right? Take it further than the end of your driveway and drive it.
Is the sound present when you actually drive the car on a road (other than the end of your driveway)? I understand what you said - it does not make the sound in gear, it only makes the sound when in neutral or park. But, let's see if that status changes while actually driving the car, then stopping the car (while in gear), then moving again & then stopping and putting the vehicle in neutral or park.

NOTE: Try this (since it stops starts making noise in neutral or park). While driving the car down the road shift into neutral - does the sound go away (stop) begin?

EDIT: Sorry, my brain is scrambled - it's late, forgive me. The sound appears only when in neutral or park. Still, take if for a drive and shift into neutral while driving, does the sound appear as soon as you shift into neutral? If so, is there any cadence to the sound? IOW, does the sound increase in speed or decrease in speed relative to driving speed?

NOTE: Does this sound increase or decrease in speed with engine RPM while in neutral or park?

 

Double check your trans bolt to the back of the block are all tight. I had a 65 GTO years ago, auto trans that did this very same thing. Took it to a couple mechanics, both told me main or rod bearings.. I started listening and looking real hard because I didn’t believe it. The trans bell housing bolts had loosened up, the flange was slapping the block and idle causing that rhythmic knock. Tightened them all up, problem solved. It’s worth checking, at least eliminating that.

 

you said the flex plate was wobbeling fix it

 

Remove the oil filter, use some tin snips to cut it open. Look in the filter media, if there is no metallic debris you can relax. The noise is not bearing related, look elsewhere for the noise.

 

Let's backtrack for a second, just to confirm something. You say the sound goes away when you put it in gear. So at idle in gear (which will be a slower speed than at idle in Park or Neutral) the sound is completely gone? What if you load it up against the torque converter (only back up to the same speed it would idle at when not in gear, though) while holding the brake? Still no noise?

 

Well I drove it about a mile down the road and turned around and came back home . Now its heard no matter if in gear or not . And it's louder .so I unbolted the torque converter started it and even with torque converter unbolted it's still there . Before it would stop if I unbolted the TC . I have a video I'm going to try an upload

 

Any advise on how to upload a video ?

 

Post to YouTube is the best option. Most videos are too large for this site. But if small enough, you can upload a video as you normally would an image - MUST be <10MB.

 

There was one key test you haven't tried suggest by BangScreech - you know how to brake torque the engine, yes? Does the sound get louder &/or decrease when brake torquing the engine (while in gear of course)?
Thinking about your scenario - any chance the starter bendix, etc. is touching the flex plate and not fully returning after you start the car e.g. hitting/rubbing on the flex plate?

 

Have you tried running it with all belts removed to rule out an accessory or pulley?

 

Ok I posted a video on you tube called ( bearing , rod , or what )

 

Click on the YouTube video where it states "Share"/Copy, then post that URL link into this thread.

 

 

Flexplate.

 

Did you ever replace the flexplate, you said was wobbeling? Remember, back in post # 7 ? You stated it was wobeling.

 

Naw lost my job a little bit before then so my money was short . So had hoped I could slide on that for a few just to get it back together. The few places I seen back then was wanting $100 plus for one but I found one at napa for $56 and they do after which is like buy now pay later every two weeks will be 14 and some change . Have to do a little more work now separating the trans but it's ok . After making this video I shared on here to show everyone my question of the flexplate I can see very well that that just could be the problem it looks so simple in the video to pin point but it wasn't at the moment. I had thrust bearing thoughts and many other sinerio all because I put it together myself . But I got to thank you all because this journey has been a good one to have with knowledgeable guys like yall to help thank yall !!!

 

And...now you're a veteran w/ the ability to create/post a video to YouTube & upload the URL link. Win, win.

 

thanks to a family like you guys I can't wait to finish 79 cutlass and start my next . Thank you !

 

Good luck with your car. Hope you find suitable enployment soon. Merry Christmas

 

Stupid question time: did you check the bolts connecting to the torque converter? That should be able to be done without separation.

 

I had this exact same issue on a 1960 Plymouth Valiant with a slant-6 and auto trans so it is not just a V-8 thing. Check all your assembly bolts.

 

Was your issue ever resolved?

 

did you put new cam bearings in during the overhaul?

or replace the rear cam soft plug?