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1983 300D 5speed
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30 Posts
Discussion Starter #1
Hi all!
Trying to eliminate a low engine speed related noise and resonance over the last two years and after changing various parts on my 1983 300d 5 speed, i was inspecting the bearing bracket last weekend. i have read that when you install it there is a shoulder that must face toward the rear of the car. The picture below is taken from the rear wheel side of the car. Is it installed correctly? As i dont understand what exactly is the "shoulder" thing on the bracket.
2606867
 

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Diesels om616 -> om606
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476 Posts
low engine speed noise, or speed-noise?
if its relatable to the engine-rpm id check the engine-supports+gearbox support.

what sort of noise is it?
from the picture i cant say i see anything wrong with the mounting in itself. it might be 180degrees wrong, but im having a hard time seeing that would cause, engine-speed related noises
 

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1983 300D 5speed
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Discussion Starter #3
Low engine rpm. It is audible in all gears but especially in 3rd and 4th. It is a resonance sound. In 3rd gear at approximately 30-40 km/h, in 4th at 40-50km/h in 5th at 50-60. Above 70km/h up to 160km/h you dont hear anything at all. The car drives like a dream. I have already changed engine and transmission mounts, centre bearing with its carrier,rear differential mount, the differential itself and rear subframe bushings. The sound is still there
 

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'86 W123 200, OM617 non-turbo, bastard 5-speed; '95 W202 C250 Diesel, OM605 non-turbo, 5-spd man
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4,112 Posts
I could be wrong, but if the noise occurs at different road speeds in different gears, the vibration most likely comes from the engine. If it were the propshaft, I'd expect the noise to happen at the same speed regardless of the gear or the engine speed.

Quite frankly, you are driving at too low speeds. I would never engage 3rd gear below 40km/h, 4th below 60km/h or 5th below 80km/h. That is a recipe for destroying your transmission and/or your engine. Take a look at the speed indicators on your speedo. Those yellow or orange stripes that represent the highest allowable speed in that gear? Take between 2/3 of each of those as the minimum shift point for the next gear.

There is a general misconception about automotive diesel engines be "low speed engines". Just because a car diesel engine cannot rev as high as an equivalent petrol engine, that doesn't mean that it is a tractor or bulldozer engine. Automotive diesels are still happiest between 1/3 and 2/3 of their rev range. In fact, since I have a rev counter, I always keep the engine speed above 2000rpm in 3rd gear or higher.
 

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1983 300D 5speed
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30 Posts
Discussion Starter #5
PlaneCrazy
I understand your point and thank you for mentioning it.
If it is engine related why it is not audible with the car parked and the gearshift in neutral?
and why the noise stops as soon as i press the clutch while the car is moving?
it doesn't make sense to me and i try to find a solution because it is really annoying while driving
 

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'86 W123 200, OM617 non-turbo, bastard 5-speed; '95 W202 C250 Diesel, OM605 non-turbo, 5-spd man
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4,112 Posts
Very simple: there is no load on the engine in neutral or when the clutch is pressed.

This will also explain why there is little to no noise in 1st and 2nd gears.
 

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'89 300E Turbo project, ‘85 Audi Coupe Quattro, ‘71 BMW turbo 2002, '73 BMW 2002tii, ‘67 Kaiser M725
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17,617 Posts
I notice there is no load on center bearing support bracket. Like totally relaxed. Centered?
 

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1983 300D 5speed
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30 Posts
Discussion Starter #8
Nutz 4 Benz
What do you mean by no load on the support bracket?
The picture was taken with the wheels on the ground.
 

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'89 300E Turbo project, ‘85 Audi Coupe Quattro, ‘71 BMW turbo 2002, '73 BMW 2002tii, ‘67 Kaiser M725
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17,617 Posts
The slotted holes where the 2 bolts hold center support. I notice they’re maxed at loose. If you push bearing forward to load, then tighten, maybe noise will go away.

I played this game on my old BMW, was your noise same as mine?

 
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