I've tried talking to the car, but it's not giving up the answer. Here's what I've got:

About a month ago, I have three tires installed (to complete a set). About a week after that, I R&R rear shocks. Now, sometime between tires and shocks, **** I think but am not sure on exact timing, but it's at least after the tires **** I start to head an ever so slight clicking which seems to be emanating from the rear driver side wheel area. A light clicking almost like a baseball card in a bicycle spoke. Only present at low speeds. I assume it's the new rubber nipples on the times and don't pay much heed. Until the clicking gets louder and more certain, not a baseball card in a spoke now but a bonafide auto problem that sounds like it might potentially want to ruin my day. Starts to sound a little further in from the wheel.

I've been keeping my eye on the underside and notice that the differential is wet, especially the front. I change the fluid there, cross my fingers so hard I brake three of them, but clicking persists (fluid was low but not dry; first time I ever did the job in 4 years/40k miles, no idea when it was done before that). No leaks. Car runs as is always has, with a bit of a squeak when reversing and sometimes when steering. Clicking though is now more pronounced, a real sort of metal hitting metal (not hard) between about 5mph and 20-mph when it seems to go away.

Clicking ONLY is present when accelerator/drive shaft is engaged. As soon as I left off the pedal, no clicking, just cruising.

Here are some questions I do not know and cannot get a boat captain to play along with (I'm in Kodiak, Alaska, on my own). Does anything spin/rotate beyond the differential when accelerator is engaged? If not, I'm probably looking at something like a driveshaft bearing? But if the axles or wheel parts are only engaged with accelerator, then I have a lot more options, I'd imagine.

Any guesses? Anyone want to come hang out and fix a car in Kodiak while I go hiking?

Any help is really greatly appreciated (I've become spoiled, not really interested in traveling around in anything less than an early 80s S-Class). I have no junk yards. Plenty of non specialty tools and a slew of maintenance mechanic "friends" (fish processing machine mechanic types) that would just love to watch me try and fix this thing.

For whatever it's worth, 1982 300SD, 344k on everything except everything under the hood, which was replaced under warranty at 104k.

Based on your description, I'd be thinking half-shaft or wheel bearing. It is possible you could have a flex disc or carrier bearing problem in the driveshaft as well. I'd check the flex discs for cracking or breakage just out of caution. The carrier bearing or driveshaft issues usually will seem like the problem is behind the center console.

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Current stable:
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1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
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1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]

CV joints.
What do your CV boots look like, condition wise?

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

Clicking is usually a bad CV joint. Is it louder on one side than the other?

If a CV is worn, then you can usually get a "second life" by swapping rear axles left and right. The wear pattern is directional, so doing this will give you quiet for a few more miles. The right way to fix, of course, is to replace the offending axle.

If the cv boots are intact add a little heavy oil to them. One at a time is best to locate the noisy one. If a cv boot is torn and leaking is another indicator.. Both are ways to verify it is the cv joint usually. Normally it is the outer joints that cause issues.

You have to catch them early enough before they are really damaged in this test. Once the noise becomes a constant it is normally too late. The longer you drive on one like this the more damage to it occurs. Initially they are just dry and you hear the release clicking.

Actually I consider it part of normal maintenance to add a little heavy oil. Especially just after the initial purchase. There is too strong a chance after thirty to forty years that some oil has escaped. For the very small amount of time it takes to me it is good insurance. Had they been packed in grease at the factory I really believe none of them would have lasted as long on average as they have.

The grease that is basically oil with a soap additive to massively increase the viscosity. Over time bleeds the oil component out and becomes a crusty leftover. Many failed joints I have taken off and examined on other brands of cars. Show pretty conclusively the grease had failed to lubricate anymore. So the joint wore out. Many of them where only about ten years old.

Mercedes use of heavy oil really impressed me. Time in my opinion has proven it as well. Some of these cars have un godly total miles on those joints already. If the oil has stayed in many if not most are still good to go. If for example some oil is added and the joint goes quiet. I would feel better off than putting on the cheap new Chinese made replacement axles. I have had very bad luck with some of their parts to trust them to last.

The classic test to diagnose a bad joint on a half-axle is to weave side to side at highway speed, and pay attention to the noise the car makes. If you can detect more noise in either direction, you've got a bad joint on one of the rear half-axles. For instance, if you turn the wheel right (so the car leans to the left, and the left axle has more load on it) and the noise gets louder, than the left axle is the problem.

If any of the axle boots are torn and leaking, that joint is ruined and you need either a good used axle or a new axle. Special tools required to take apart the joints and put new boots on, generally most people decide to get new axles.

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

They don't look that bad. No rips, no holes, a little light cracking but none of it seems to go through the boot itself.

I appreciate all the replies so far. The thing bothering me is that the noise, which I would describe as a clicking, started the day I had the tire put on. Most of the stuff I've read about cv joints describe it as a clunking. Can anyone humor me by offering any potential, even if unlikely, ways this could be related to the tires going on? I can also note that those calipers are in rough shape but I don't see any possibility that the noise would come from there exclusively when accelerating.

Check your wheel lugs.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
97 C280 147k miles

Take the wheel off and check for damage or foreign objects. Put wheel back on, raise car and spin wheel by hand. A piece of gravel trapped near the caliper or in the heat shield can cause this. There is also a bolt through the rear axle to the wheel hub which has a special washer that is one-time-use-only. If that washer fails, the bolt backs out, and you can have a clicking as the axle moves in and out of the wheel carrier.

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

What is the condition of the rear swaybar links?
Maybe they gave out if they are old.

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