Ahh so I think my flex discs and drive shaft center bearing are going bad. I've been developing a thunk thunk thunk (similar to the noise you can make yourself if you close your mouth and tap your teeth together). It sounds like it is coming from the rear.

The sound is incredibly intermittent. I have a hard time recreating it. The first time I noticed it it was REALLY loud. This was back in October, but my gallon of motor oil had managed to find its way into the well in the trunk. When I took it out, the thunk has gone away.

Well now on really long road trips (which i've been doing a lot of). A very tiny tap tap tap appears to be coming from the rear. I was able to recreate it very slightly if I slowly accelerated between 55-60 mph, but as quickly as it came it disappeared.

Could it be flex discs and drive shaft bearing or something as easy as loose plastic rattling in the trunk (silently wishes for the later)?


This thread offered some insightful points. http://www.peachparts.com/shopforum/showthread.php?t=165076
I'm going in for a rotation and snow tire install on monday. I'm going to ask my mechanic if I can take a look under neath of the car. Is there anyway to diagnose this now before I head in?

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My spare tire makes a racket when it isn't perfectly tight, almost the noise you describe...worth a check at least

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TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth

Could be the CV joints as well as the flexxdisk. Check BOTH!

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Ian White

1995 E300 Diesel w124 OM606
2014 E550 w212 M278 biturbo

2001 BMW 740i E38 M62 (past)
1981 300SD w126 OM617 (past)

I recently changed the center bearing after getting a) a rapid thumpthumpthump accelerating from a stop and b) a helicopter-like sound at highway speed and near-neutral throttle. Does either of those sound familiar?

IME a bad axle joint is a sharper sound than the driveshaft carrier, more like a metallic knock. But once you start crawling under the car, you might as well check everything.

Check balance on tires.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Sounds like cv joint possibly.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I tried recording the sound with my phone, but I couldn't get it through.

If this at all helps when my tank is registered as under half full the noise tends to manifest itself more.

I'm right now I did about 40 minutes of driving and no sound with about a nearly 3/4 full tank. I'm going to crawl under today and take a look.

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Remove the bottom of the rear seat and have someone drive you around while you listen. That noise "exactly" decsribes a bad axle (at the CV joint). Passengers side was bad in my case. Grabbing the axles by hand to check them showed no noticeable problems. Only while driving.

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AJ

1985 300D (SOLD)

Hello, have you tried the sway bar link...my car made a thunking noise intermittant but only under turning situations. The sway bar link is a white plastic part in the rear wheel location. The original was not white on my car, but the replacement was, try to look up the part on the buy parts category so you know what to look for. It is behind the brake backing plate (rear wheels)...one on each side. (follow the sway bar) Make sure to move it around to see if it is broke as mine looked intact until I got a light in there to move it around and then I saw it. It is cheap to fix, might as well check it.

Yeah they were r&r when I pulled the car out in june. Both were bad, but cheap to replace.

I hope it's not an axle. That is cash I definitely don't have right now.

I'll pull the seats and listen. Right now there isn't any noise at all

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O.K thought to mention as I had that happen on my 79 300d.
I am trying to find a thump on the fiancee's 300TD. It only happens at a certain speed on that one. 50-60kms/hr. I bought a new center bearing bracket/bearing and dust cap and one flex disc. I am saving up for the second flex disc and then I will take it apart. I am hoping it will hold on until then and hopefully that fixes the thunking on the wagon. I have no problem throwing those parts at the car since they are probably 25 years old and I don't want to have the driveshaft let go. Have you seen the picture of the guy that had the driveshaft let go under speed..... scary.

My axels made no noise after the grease leaked out of old dry rubber flexors but I changed the axels before they were totally dry, although I am sure they would have started making noise if the did go dry.
I read something about swapping the right side axel for the left axel to counter the wear pattern that the balls make in the cup portion of the assembly , but if you go to the trouble of opening up the stinking diff. then I changed them altogether as that remedy is a quick fix deal in my opinion.

Somebody on here told me that the previous owner may have put the two driveshaft sections together the wrong way and that could lead to my thunking noise. I have not looked if that is my case yet ,but I am not sure how to tell if that has been done .
What does a properly linked driveshaft look like? how to tell if it is wrong?

Initial impression is that the body in the trunk has either achieved 100% rigor mortis or has frozen due to the change in the weather.

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Strelnik
Invest in America: Buy a Congressman!

1950 170SD
1951 Citroen 11BN
1953 Citroen 11BNF limo
1953 220a project
1959 180D
1960 190D
1960 Borgward Isabella TS 2dr
1983 240D daily driver
1983 380SL
1990 350SDL daily driver alt
3 x Citroen DS21M, down from 5
3 x Citroen 2CV, down from 6

Probably. I had to move her around to fit in Jimmy Hoffa. I'm pretty sure my car's trunk is rated as 2.1 Jimmy's or 8 dead prostitutes so either way that shouldn't be the issue.

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Realistically only about seven dead prostitutes; those ratings are inflated a bit. Maybe in California you could fit eight, but around here the hos aren't as tiny as they were in the 80s.

Seriously, though ... do check your flex discs, although a worn flex disc would more likely result in a vibration or, if it were really bad, a rhythmic thumping/clunking. Check them anyway. You don't want one to go. This one was fixable, I was lucky:


I'd crawl under and check out anything you can see in the rear. I'm not sure what the differential mount set-up is, but it could also be that, or a subframe mount. Or as others mentioned, an axle.

The other day I took the 240D out for a countryside drive and kept noticing a random, rather loud thunking from the back. I pulled into a local grocery parking lot got out, and noticed the trunk wasn't shut. Oops. I'm guessing you've ruled that out ...

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1987 300D, arctic white/palomino--314,000 miles
1978 240D 4-speed, Euro Delivery, light ivory/bamboo--370,000 miles
2005 Jeep Liberty CRD Limited, light khaki/slate--140,000 miles
2018 Chevy Cruze diesel, 6-speed manual, satin steel metallic/kalahari--19,000 miles
1982 Peugeot 505 diesel, 4-speed manual, blue/blue, 130,000 miles
1995 S320, black/parchment--34,000 miles (Dad's car)

Thanks Cecilla,


I just crawled under to take a look. Thankfully the rear flex discs looked perfectly fine. Dirty since they seem original and I couldn't see any cracks or furry unraveling.

I tried to get a good look at the front, but without car jacks and a stand I can't turn my head around to see much of anything.

I'm going to my old mechanic who did work on my honda (he still mounts and rotates my tires). I'll have him lift up the whole vehicle so I can get a much better look.

Flex discs and drive shaft bearing. What else should I grab and pull while I'm under there (no that's what she said comments)?

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