We love our '81 300TD but, let's face it, once you get up to 60+ on the highway there is a lot of noise.

As far as I can tell, there are 3 types of road noise more or less audible, on any car: wind noise, tire noise, and engine/drivetrain noise.

I've heard some people say that any wagon will be noisier than a sedan of the same model due to layout

I think that most of mine is engine/drivetrain noise, and wind...

If I wanted to trade up to another diesel engine but wanted something a little quieter, what would it be?

sedans are definately quieter. the 124's have much better noise insulation too.

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1991 300 D 2.5 Turbo, 220k
also in the family:
1981 240 D 185k
1991 350 SD 185k
2006 S 500
2005 SLK 350

300SD's are much quieter - I can barely hear my engine at 60. In my 240D, that's all I hear.

SD's have two firewalls and LOTS of insulation. Big difference.

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1984 300Sd 210k

Former cars:
1984 300D 445k (!!) (Strider) Original (and not rebuilt) engine and transmission. Currently running on V80 ( 80% vegetable oil, 20% petroleum products). Actually not, taking a WVO break.
1993 300d 2.5 275k. Current 120/day commuter
1981 300SD 188k (Hans) Killed by a deer

Generally the newer diesels are quieter. There's a big difference between my two W123's and the W124. The W124 doesn't even sound like a diesel when it's above idle and it's very quiet even at highway speeds, that's why I prefer the older diesels. But if you want an ultra quiet vehicle you're hanging out in the wrong crowd because you need to get a gasser. The quietest car I've ever owned was a Civic Hybrid, but it was definitely not my most favorite.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

The OM603 is noticeably quieter at speed than the OM617. The 300SDLs should be less noisy than your current car, both due to the superior sound insulation, and the more refined engine. If you get a good one, the 350SD/S350 is exceedingly quiet at speed. I expect the newer engines are quieter still, but I have no direct experience with them.

Someone on here did a homemade sound insulation installation with pictures a couple years that reportedly made a real dent in the noise. Maybe Leathermang? Not sure, but I'm sure you could find it with a search if you're interested.

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Tjohn

82 300 SD
77 450 SL (gone)

I think station wagons sound louder because there is more interior surface to transmit noise into the cabin, and probably because they're a bit more flexible. My Suburban is very noisy.

My SDL is very quiet on three scores (road, engine and wind) but has a soft spot in the muffler so it mutters a bit.

It seems quieter than the 85 SD I had for a while before I crashed it, probably because it is quieter.

My ex-wife's 96 E300 Diesel (W210 body) was probably the quietest car, diesel or no, that I've ever driven.

Regards,

Jim

My SDL is quiter than my Toyota was on the highway, they are a very quit car.

The most silent car I have ever been in:
S600 and an S430, the 600 was almost to quit.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

My 1985 300D is anything but quiet, but I love the way it sounds at 75 to 80 mph. With the windows closed and the radio off, you can really hear it hum.

My '80 300TD is noticable quieter than my tractor, at any speed...

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

The W123 diesel's aren't known for being quiet. I would have to agree that the W124 and W126 diesels are MUCH QUIETER... Engines with turbos are also much louder than n/a engines...

I'm a great 81 to 85 SD fan and granted there are probably quieter models but my SD;s are quiet enough to hold a normal conversation in but not erie quiet like some other makes and models.With the correct exaust system I consider them luxury car quiet with a pinch......

William Rogers.......