Technical 53 Chevy - Beeping Noise when Stopping

I don't know, just throwing this out there. Somebody probably knows more about it than me, but could the trans vent have something stuck in it, partially blocking it, so it makes sounds? I've seen some strange things.....

 

At this point with all the ideas from the forum and nothing that helped, I think the only way to fix this is to have it rebuilt by a good trans guy.

 

Interesting as well. Could the pressure release from the trans happen only when the engine is running if the vent was blocked? I'm still trying to figure out why I had no noise when I shut off the engine and let it coast to a stop after being in second gear, then put it in park and started the engine and the noise came right in.

 

For sure. I was originally just trying to prove it was coming from the trans. That's why I took it to a transmission shop but they were not of much help. I haven't had time to instrument the car with microphones and/or cameras as some suggested. I've just been able to drive it and disconnect the vac line and have my friend run along side to see if he can pinpoint it.

If I knew it was coming from the trans for sure, I agree, would have to have it rebuilt it seems.

 

No idea, just a thought. Seems like everything else has been thought of.

 

I'm still thinking valve body or pump buzz. The modulator is a cheap and easy thing to rule out. You did check/ change the rubber vacuum hose to it I believe. That noise used to be common years ago and a rotted hose was often the cause.

 

How is the manifold vacuum connected to the vacuum modulator? Is there a steel tube with a rubber hose connecting both ends to the engine and trans? If so, is there a section of the steel tube that is crimped to form a restriction in the tube? This was commonly done in production to dampen the vacuum signal to the modulator and make it slightly less sensitive. They would get plugged or restricted occasionally and it was a simple fix to cut out the crimped section and replace it with a short piece of vacuum hose.

 

On the ChevyTalk forum, poster stated he disconnected the modulator line, at the engine, then plugged the vacuum port, at the engine. Same sound was the result.
There have been so many, many replies, but, all the replies, mine included, are really nothing more than guesses to a very odd situation.
For a 3 second BEEEEP, which happens most of the times, IMO, I would drive it until something changes.

 

Thanks I replaced the steel line and rubber line as well. I didn't replace the modulator.. Maybe I should anyways just to rule it out? With vac disconnected and plugged at the intake it still made the noise.

 

Thanks that is true and probably should just keep driving it as is.

 

Thanks for your help. I recently used 1/4" brake line and cut the ends off so there is no flare. I used proper size rubber hose on both ends.

 

Yep... guess I missed that part...

 

The thing that puzzles me is that the noise only happens with the engine running but must have already been in second gear when slowing down. Or shifting from drive to neutral .. Or starting the engine immediately if shut off when slowing down and already at a stop.

If it's engine related it has to be under a specific loading condition for the leak or whatever to release. Revving up the engine in park and letting off doesn't do it. Something in the engine has to buildup and release and can only happen while it is on.

If it's the trans something is building up and releasing when the engine is turned back on but in park. Maybe something on the input side of the trans spins when the engine is turned back on and the stored buildup pressure or vac can equalize and result in the noise?.. If it's related to the modulator I would think the noise may have gone away when I disconnected the line from the engine but it did have a slightly different tone. Maybe some crap inside the modulator or its old and the tone changes when vac is pulled on it during the 2nd to 1st gear downshift? Funny thing is it shifted so much smoother when plugged back in so it seems functional but could still be the culprit.

The day this is figured out I'm sure a lot of people will be curious to know what it was. Hope it happens but been so busy to touch the car.

It seems next time I have a chance I should change the modulator since it's cheap and perhaps I'll get really lucky.

 

Not to say it isn't possible, but seeing the noise is still there with the modulator line disconnected at the engine, and the engine vac. port plugged, I would not think the modulator is the culprit.

 

Hmmm yea. I wonder if it would be stupid to run a hose from the trans vent into the car and see if i can hear the noise from the hose while driving.

 

At this point, any option is worth trying, if you are willing. Can't hurt, right ?

 

Just don't inhale

 

Nor put that tube inside my ear to hear better

 

Agree that the modulator is ruled out. Be funny if it was the vent doing the funky chicken all along.

 

Actually, holding it up to your ear might not be the worst idea. Think stethoscope...

 

That's what I was originally thinking but would be hilarious and annoying if I got a little more than I asked for out of that tube in the form of red trans fluid

 

Dammit......i got wrapped up in this thread about 2 pages in and said surely with 9 pages of posts this is fixed so I kept reading. The suspense was killing me, only to be let down in the end....ha.

I have trans noise gremlins too, nothing like yours, probably worse, but its a 400 not a 350. Good luck....

 

I know, I hope if it's trans related I can hear it through the vent tube with a hose as a stethoscope. Either way eventually this has to lead to a solution or a part breaking down further after which case I'll be sure to inform everyone what the culprit was.

 

Some more time has gone by and I haven't had a chance to do anything except I put the car on jackstands this morning. I can't tell if the TH350 trans vent bore has a hole on the side that I can't see in the photos, otherwise it looks purposely plugged. I cant stick my head that far up to see so I had to use my iphone to take photos. I tried with a mirror and light but couldn't see anything well.




Nonetheless here is what I plan to do on my drive in a few minutes.
1. Listen to noise from the vent. I put a 6 inch piece of tight fitting plastic tube in the trans vent bore. Smaller tube shoved into the bigger tube and then running that through the floorboard master cylinder access and enough length that I can put it in my ear. It's small diameter but it's all I had. It should pick up noise as I tried tapping on one end before and I can hear it.

2. I removed the fresh air tubes on both sides and the floorboard piece that covers the master cylinder. I hope I can hear which of the three is loudest.

3. After trying the first two, I'll pull the dipstick tube out so its free floating. Maybe the vent is plugged and I can't tell.

4. Spray some carb cleaner around the carb gasket. Early in 2015 I had to take one of the cylinder heads out and I had reused the gaskets on both sides of the spacer. I'll spray around the gasket when the engine is warmed up and idling and see if the idle changes.

Hopefully that will give me some more clues.

Lastly I read somewhere that someone had reported whistling noise but their transmission shifted fine. They cleaned out some "goo" from the modulator and the noise went away. There was some dirt and junk in the hole of mine which I cleaned with a paperclip but I didn't take it out and heavily clean it. If I removed the vac line and the noise didn't go away it's hard to imagine anything inside the modulator making noise unless the pressure in the trans is vibrating the diaphragm and transferring the vibration to stuff inside. Is that far fetched?

 

Update.
Drove it until it started making the noise when slowing down.

- Spraying carb cleaner around upper and lower gaskets around the spacer did nothing to the idle.
- Opening the dipstick tube by pulling out the dipstick tube did nothing to change the noise.
- Listened to the noise with the tube coming out of the trans vent and I didn't hear anything louder that way. I did hear some mechanical noise probably related to the trans in general but not in sync with the noise.
- Tried listening with the floorboard access hole for the M/C open, and with the two fresh air vent tubes off and vents open.. Could not hear the noise louder from any direction.

Owell at least I tried.....

 

Sorry to keep this dumb thread going but I finally have a little time to look into the beeping noise again and it's still doing it.

I'm going to drive it for 15 min until I hear the beeping noise and then back it in to the garage and put it on jackstands and Fire it up and have a friend put it in drive and I'm going to listen from the ground laying on the side.

I shouldn't have any issues with safety? One friend who was going to help me said that's sketchy and my roommate says she doesn't like this idea but do whatever I want. I'm going to face the car outside just in case the unthinkable happens but I can't see why it would fall of the stands in drive and the trans shifts rather smooth under a load.

I could also go to a side street where ice seen a bunch of campers and probably wouldn't get hassled there. Any thoughts?

 

I've run cars on 4 jack stands before without incident. Just don't get under it, just in case. Nest to it should be fine.


Sent from my iPad using The H.A.M.B. mobile app

 

Or throw a couple old tires W/rims under it. Just in case. And chock the front wheels.

 

Thanks I was able to do it without needing old tires under it and incident free

 

Thanks for your help I went ahead and tried it.