Help with this noise please. It wasn't the flex plate - PeachParts Mercedes-Benz Forum

progun · #1 08-05-2008, 08:28 AM

I have a horrible grinding noise that is worse on startup and comes and goes when I put it in gear. Under load it gets louder as well. I thought I had a cracked flex plate that was letting the torque converter move but upon inspection I found the plate to be perfect. Is it my torque converter? It is a loud metallic scraping sound. I want to drive again. It is on the lift disassembled right now. Thanks, Paul

It shifts perfectly by the way... Thanks

Diesel911 · #2 08-05-2008, 11:26 AM

Get a mechanics type Stetoscope or cut Broom Stick or something else you deem suitable to put against parts of your car and carefully put your ear at the other end and see if you can find where the sound is comming from.
It should be louder closere to the problem.

progun · #3 08-05-2008, 02:40 PM

It is definitely from the front of the tranny in the area of the torque converter and flywheel. That is why I made my initial diagnosis on the flex plate. The plate is perfect. I already have it apart and I don't see anything visible. I am leaning toward the torque converter itself. Paul

Diesel911 · #4 08-05-2008, 04:56 PM

OK.
Nice to have a lift!

progun · #5 08-06-2008, 08:44 AM

Yes, it is a friends and it makes things easier. A company that rebuilds torque converters says it probably is not that. He says the reverse bands in the trannys break causing this metallic scraping. I will pull the pan tomorrow and check for metal. Paul

Moorewr · #6 08-06-2008, 09:20 AM

If you have to rebuild the tranny, DAACO in Cookeville TN has a kit for around $250 that I used in my 77 and it has been good for over a year. You can find them on line, think I spelled the name correctly.
Ron

vstech · #7 08-06-2008, 09:30 AM

front pump? imput shaft?

progun · #8 08-08-2008, 07:14 AM

I pulled the pan last night an no shavings. It looked like new in there. Input shaft is shiny as new. Has anyone had this noise before and found a solution. It screamed really bad right after start up then would go almost silent. In forward under load it shifts perfectly but the is a "ring, ring, ring..." metal scrape that changes with load. At low speed in reverse it is loud as well.

fdanielson · #9 08-08-2008, 10:54 AM

Over the years I've had a few starter bendixes fail and cause interference with the flexplate or flywheel. Try pulling the starter and look for signs of metal to metal contact.

Or if it's on a lift you may be able to pre-loosen the starter bolts, tighten them up just until there is no slack, start the car, and the loosen the bolts a bit to see if manipulating the starter position influences the noise. Of course doing anything near a running powertrain can be quite dangerous.

progun · #10 08-13-2008, 05:05 PM

It looks like the transmission center shaft is loose. It allows the vanes of the torque converter to scrape the inner housing. I will pull the front cover off the tranny tomorrow night. This shaft is connected to the planetary gear in front of the tranny so I may need all the front tranny parts. I will update tomorrow. Thanks, Paul

KarTek · #11 08-13-2008, 09:32 PM

Hey, that's great Paul! It's nice to nail those mystery sounds.

pawoSD · #12 07-05-2009, 09:30 PM

I have a similar sound that developed on my 300SD today after a 65 mile trip....at my destination there was no sound....after I got back, noise was there. Its a "shhh...shhh..shhhh...shhh....." scraping sound when it is in park/neutral, or while driving along in drive/reverse at higher speeds. The sound disappears when the trans is dropped into drive or reverse. No vibrations at all....shifts fine, all gauges fine....the sound is coming from the torque converter area (verified with mechanic scope).....the sound changes with the speed of the car/motor rpms. No idea what it is. It seems to drive just fine and shifts the same....so I am not ultra worried.....but its still not a pleasant sound to hear a scrape scrape scrape while driving...

tbomachines · #13 07-05-2009, 10:38 PM

I have had a scraping sound too, but I believe it is the fuel lift pump surging fuel back into the tank. I noticed it was louder as I had less gas, it also increased in frequency as the engine RPMs increased.

pawoSD · #14 07-05-2009, 11:56 PM

My scraping comes from the front of the trans around the torque converter....its not super loud, but quite noticeable with the window down.

pawoSD · #15 07-06-2009, 02:48 PM

Further developments....while out driving today I put it in reverse and at first it felt like the car was glued to the ground (wasn't moving) so I gave a touch of throttle and it jerked back a couple feet in a Jerk-jerk motion. I dropped to neutral, back to reverse, and it engaged properly that time....I proceeded to drive several miles (forwards

), no issues except the annoying swish swish sound.....I get to where I'm going, and check the fluid, a bit low....so I added enough to get to max on the stick.....reverse continues to engage just fine....however, now it is holding first gear longer than it used to, and kinda slams into 2nd, then skips through 2nd real fast to third (when driving leisurely)......it goes to 4th normal. When going faster its not really noticeable and it holds 2nd properly.

What is going on here??

I fear my trans may be chiseling its name on a tombstone.

Any ideas or similar experiences?

The fluid is not burned or discolored and smells normal....fluid only has about 10k on it since the last change. Shifts are extra firm.....