Hi guys.

I drive a 250 mile stretch pretty often on I-75. On my past two trips, after an extended duration of 75-80 mph speeds, I start to here a knock of some sort from the rear of the car (I think?). It isn't high pitched, no grinding or rubbing noises, just like a knock or clunking. I don't think it's engine or tranny related, I'm guessing it's possibly the drivetrain/differential. Weird thing is, once I exit the interstate and slow the car down, the noise goes away. But once I get back on, after 40-50 miles, it comes back. Any ideas? Possibly something loose or that should be replaced?
Thanks.
Damon Fite ---1983 300TD Wagon---300,000 miles+!!!

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1984 300TD Wagon--Astral Silver--Retired
1983 300TD Wagon--Dark Blue--Retired

Check your flex discs!

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'81 300TD Wagon 355k (Miss Diesel)
'83 300SD 180k
'84 500SEL 190k (Parting it out)

What exactly should I look for? Will there be visible signs of wear? Is it just a matter of tightening it? How will I know if it needs to be replaced?
Thanks.

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1984 300TD Wagon--Astral Silver--Retired
1983 300TD Wagon--Dark Blue--Retired

Sounds like your CV axles. Have someone hold the brake and slowly move the gear selector from D to R a couple times while you watch the axles. If they are bad they will move around a bit.
I have blown about 3 sets of these guys and every time it was a new noise. One set was just a click at slow speed, another was a grinding sound at around 90, and the other was only under high speed cornering. Each decided a road trip was a good time to start making noise. After clicking 2 of the sets lasted 3K until I got home and pulled them, could have gone longer but they were VERY UGLY when they did come out. All the balls had fallen out, just metal to metal clanking around back there!

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1983 Mercedes 300SD
1987 Mercedes 300SDL
2001 VW Passat 2.8 AWD
2007 OM642 Jeep WK 4x4

Breckman,

What have you used to replace your bad CV axle shafts? New, used, or rebuilt? Thanks.

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150

The last 3 sets I have installed are used, and they served their purpose well. I will buy a brand new set this time around. I can do the job in about 45 min after all the swapping I have done.....

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1983 Mercedes 300SD
1987 Mercedes 300SDL
2001 VW Passat 2.8 AWD
2007 OM642 Jeep WK 4x4

O.K. I got under the car to inspect, and sure enough, the inside boot on the passenger side has a big rip in it. All the lube is long gone. I've done my homework, looking up the old threads, etc., but I have a few questions for my specific circumstances.

---Can you/should you just replace the boot? (I'm pretty sure the answer is
no, but I need conformation)
---Will a halfshaft from the local parts store (i.e. carquest) get the job done, properly?
---Do you have to replace both halfshafts at the same time. Notice that I'm not asking should you , because I know that you should. Do you have to , or is it just a good idea?
---Are the halfshafts for the driver's and passenger's side of the car the same size, that is, the same part?
thank you
Damon Fite---1983 300TD Wagon

__________________
1984 300TD Wagon--Astral Silver--Retired
1983 300TD Wagon--Dark Blue--Retired

---Can you/should you just replace the boot? (I'm pretty sure the answer is
no, but I need conformation)
Can be done, but you need some special & expensive tools!!

---Will a halfshaft from the local parts store (i.e. carquest) get the job done, properly?
The jury is out on this one. Some have had good luck, others not.

---Do you have to replace both halfshafts at the same time. Notice that I'm not asking should you , because I know that you should. Do you have to , or is it just a good idea?
I did not, because only one boot was shredded!!

---Are the halfshafts for the driver's and passenger's side of the car the same size, that is, the same part?
Yes, and this can allow to use a used shaft on the other side of the car and potentially extend its life.

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150

I had the same noise and had no idea what it was. At least it sounds like the same noise. If I cruised at around 80+ for over an hour-I heard this loud thumping sound like someone was stuck in the trunk and trying to break out. I haven't had it looked at since-I've been off the highway and the car is in the garage until spring. We'll see...good luck to you and fill us in.

Orkrist,

Did you ever let the guy out of the trunk?

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150