‘83 300D Vibration / Noise under load - I’ve tried all of the common things

[dinman]

1983 300D, Turbo, Auto. Relatively new to my friend, and trying to assist chase down a vibration / noise.

263k miles. Very nicely preserved car. Pastel Beige / Henna Red, one owner from 1982-~2016, then passed to his good friend before he passed away. We acquired it from the friend. Very clean interior, entire glass out - trim off paint job in 2012 - an extremely good paint job at that.

I think the friend that acquired it let some deferred maintenance build up. He owned it from 202k-260k.

Here’s a description of the noise.

Noticeable from 2000-2600 rpm, most prominent at 2200-2400.

Most noticeable at 55-60 MPH, but can be heard at the beginning of some other gears.

Directly related to load. Lightly loaded up, uphill, louder. Letting off the throttle, it vanishes.

If modulating the throttle, the selector can be slipped into neutral at 55mph, revs held identical, and the noise entirely vanishes, along with most of the vibration.

Noise is an irregular, metallic sounding, groaning or growling noise, and is accompanied by a faint vibration.

The noise can be felt well in the passenger floorboard with the carpets removed, around the area where the tail of the transmission is. Sticking your head in the passenger footwell, it is loudest. Not as loud in the back, or the driver side.

It never does it on deceleration, and it doesn’t seem to sound any different than another healthy OM617 in park and holding those revs. It seems to only do it under load, or light throttle around 50-60 mph.

At 70-80, the noise disappears, and the vibration is very, very faintly present, in a harmonic “woo-woo-woowoowoowoo-woo-woo”. Extremely faint

Although I haven’t really looked into the brakes, I don’t immediately suspect them. It doesn’t pull under braking, and I don’t see any hot wheel temps.

I’m suspecting driveline, somehow.

All of this work has fixed other issues, but just makes this issue more noticeable.

I bought it in southern Idaho, and drove it to my friend in Atlanta GA. Before this, I did the following.

Valve adjustment
All rubber vacuum junctions
Fuel return lines
Diesel purge
Fuel filters
Cigar hose
Air cleaner mounts
Air cleaner U pipe seals
All belts
Checked crank pulley / balancer torque
Power steering fluid / filter
Coolant change / radiator flush
Coolant reservoir
Oil change

I made a pit stop in my home town in Louisiana on the way from Idaho. In Louisiana, I did the following

CV axles
Glow plugs / reamed
Oil pan gasket
Turbo oil drain tube grommet, o Ring, and paper seal
Oil filter housing gasket(s)
Oil cooler lines
Engine mounts
Transmission mount
Tie rods assemblies
Upper control arms
Alignment
New tires / balanced
Checked brakes (no funny wear, hoses look a bit old)

Now, in Atlanta, I have done the following

Checked Starter bolts (Changed before, suspected it loose)
Checked flex plate bolts (tight, no visible cracks)
Replaced flex discs / hardware
Replaced center support bushing
Replaced center support bearing
Changed transmission fluid / filter
Changed K1 spring
Changed entire exhaust, other than flex pipe

Some notes -

The previous (not original owner) changed the carrier bearing / bushings. It was a cheap URO part, the bearing felt bad, the bushing was backwards, and I have no idea if he lined the driveshaft up correctly. It’s a 11/82 build, so in theory I should be able to line the factory markings up. They were not, so I did. No change.

The top two bellhousing bolts are backed out a 1/2”, and I can’t tighten them. I think the bolts are too long. They are definitely original bolts, but seem to be in the wrong spot. Suspicious.

Trans fluid looked fine coming out. The original owner made a note in 2009 - “2qts trans fluid removed 60 miles after fluid change”. Why? Was it 2 quarts overfilled?

Speedo cable removed, no change.

It still occasionally has a 3-4 flare shift, the 2-3 was 95% fixed with the K1 spring replacement, but now it seems 3-4 is more prominent. Still kind of rare. Shift timing feels fine. Pretty firm 1-2, pretty soft on the rest unless WOT.

Engine seems very strong. No smoke, consumed <1 quart on my high speed highway drive from Idaho to Louisiana. Starts up scary fast, even in cold weather.

We are scratching our heads. The car does great, but this noise is annoying. The radio could be turned up, and you wouldn’t notice it, but it takes away from the experience. I suspected the driveshaft maintenance would maybe get rid of the vibration, leaving the noise, but it changed nothing. The vibration and the noise seem to go hand in hand.

Flex plate?
Torque converter?

Any advice is greatly appreciated.

Thanks

[dinman]

Here is a video. The noise appears around 0:11, and we let off the throttle around 0:32.

https://youtu.be/VZaAmcxzA0A?si=Y4JsIA3usyGLTZYv

[Sugar Bear]

Nice write up/explanation!

My next step would be to get the bolts correct in the transmission bell area since if they are in the wrong spot that probably means two other bolts are too short and that can cause major problems.

For the vibration it sounds like a driveline angle problem. Inspect the differential mount for collapse, the motor mounts and the transmission mount, I've read they've become hard to find. Try shimming the center support bearing away from the body.

Was the universal joint "notchy" when flexed/pivoted?

[Diesel911]

See the pic in post 31 for a notchy U-joint. Notice how it stays in position instead of flexing down as it should.

Drive Shaft U-Joint Is Staked/Crimped In Place, Now What To Do?

As far as I can remember on an 83 you are supposed to be able to use the factory aliment marks on the sections of the drive shafts. It is in the factory service manual.

See the pic in post 5
1985 300cd driveshaft?

There is something else that is fairly easy to do. The older models had similar drive shafts but the instructions concerning that large coupling nut are different.

The older method was that the coupling nut was loose enough for the saft to move in the coupling and with the care on the ground of flat with the car weight on all wheels you would put it in neutral and roll the car back and forth and then squeeze under the care and carefully tighten up the coupling nut. That is supposed to center it in that coupling.

There is a torque for the coupling nut but if it is on the ground, I don't see how anyone can accomplish that. If you had a pit as some garages do that would be easy.

[Diesel911]

There is a post in the below thread that has you can go by the factory marks on the drive shaft after a certain date in 1982.

1985 300cd driveshaft?

There is also a centering bushing on each end of the drive shaft and you need to put grease in it before installation.

You need to look for elongated holes on the yokes were the flex discs attach and use quailty flex discs such as lemforder.

Lemforder flex discs post 3.
w123 Flex Disc Recommendations??

Checking flex discs for cracks.
Checking flex disks

[imgolden]

Wow, I am amazed, I am having almost the EXACT same symptoms and I can't figure it out either. My symptoms are the same, aside from the fact that my noise is a little different than yours - it's a bassy thrum. Other than that, conditions of when and where it happens are the same (82' 300d)

My noise started after I installed a remanufactured transmission from Sun Valley. While we had the trans out, we did the flex discs and rear centering bushing on the drive shaft. Before this job, I have done motor mounts, trans mount, diff mount, axles, and many other things that aren't likely related.
I also tried shifting the center support bearing around, and retourquing various things without success.

Currently my top suspects:
-I didn't properly line the driveshaft halves back together. I did mark them, but could've messed it up I guess.
-I did not replace my center support bearing because it was an OEM part with no visible issue on the bench. Perhaps it's bad without me knowing realizing.

To address these, I plan to remove the shaft and have it professionally balanced, then take a closer look at the center support.

However, you mention that your transmission may not have been bolted back together correctly - that's an interesting observation.

Let's stay in touch. If I figure it out I will let you know, and vise versa.

[JHZR2]

I was getting a metallic noise around 2000.

Here are some videos of how pronounced it was:

https://youtu.be/pVMB3TdfgQI?si=d7-uN6-DVMOYZLjm

https://youtu.be/RswEsbVbQQA?si=1YOuIl4UWDZiJZLT

It was actually the exhaust. It just resonated at the right spot. And one of the hangars was a type that needed an 8-style versus just a round doughnut type.

It was just the right metal to metal.

The rubber hangers get saggy with age. If someone had messed with the AT it could be any number of other issues, but they may well have removed the exhaust. Any missing support (the one by the AT pan for example, which also should have some rubber parts) could be a culprit.

Just another thought based upon recent experience…

[dinman]

Well guys- it’s been SOLVED.

I pulled the transmission a few days ago, and found 2 of the 4 transmission - engine adapter plate bolts fully backed out, held captive by the flywheel. The other two were loose. It was about to get catastrophic. One bolt got smacked by the flywheel and broke in the engine. Re-torqued with new hardware, and it’s all smooth now. The noise and vibrations are gone. Now just to do some transmission adjustments, this new one is shifting way too early.

[imgolden]

Originally Posted by dinman

Well guys- it’s been SOLVED.

I pulled the transmission a few days ago, and found 2 of the 4 transmission - engine adapter plate bolts fully backed out, held captive by the flywheel. The other two were loose. It was about to get catastrophic. One bolt got smacked by the flywheel and broke in the engine. Re-torqued with new hardware, and it’s all smooth now. The noise and vibrations are gone. Now just to do some transmission adjustments, this new one is shifting way too early.

Thanks for reporting back. What made you suspect these bolts enough to pull the transmission? Why do you think they loosened?

[Sugar Bear]

Great news, good find!

[ykobayashi]

That’s good to know. Good catch. I guess it is good to have a look back there after so many years of operation. There is a freeze plug back there on the back of the engine that should be swapped out if you have it open (and you’re planning on keeping the car a long time).

My Sun Valley trans has a little bit of a growl under load. It isn’t anything too bothersome but my original trans didn’t have it. Marc @sun valley said this can be caused by gear wear. They reuse gears that have a lot of life left in them but they will make a different tone under load. After nine trouble free years of driving the car on the SV trans I don’t even notice it. I got used to it.

[gsxr]

Originally Posted by dinman

I pulled the transmission a few days ago, and found 2 of the 4 transmission - engine adapter plate bolts fully backed out, held captive by the flywheel. The other two were loose. It was about to get catastrophic. One bolt got smacked by the flywheel and broke in the engine.

What "adapter plate" is this? Did you take any photos?

[Frank Reiner]

Originally Posted by gsxr

What "adapter plate" is this? Did you take any photos?

In "Benz-speak" that is the intermediate plate.

[dinman]

I can upload some pics when I get on my computer.

I suspected fowl play because one of the top two bell housing bolts were wrong (too long) so someone had the transmission off, and back on (serial matched data card) for unknown reasons.

This is the plate sandwiched between the transmission bellhousing and the engine block. It sits behind the flywheel, and allows the transmission to be bolted to the engine.

Transmission VCV set, modulator replaced and dialed in, Bowden cable adjusted - this one is shifting wonderfully now.