rear end vibration noise - PeachParts Mercedes-Benz Forum

Marks88 · #1 09-30-2002, 09:54 PM

Fellow Posters,

I took the '83 CDT for a little road trip. My son uses it as his daily drive to and from school, short mileage. I figured it would be good for the engine, to stretch its legs so to speak. After about 60 miles a virbrating, poping sound develops coming from the rearend. The sound varys in intensity. I pull over at a rest stop for a few minutes. Nothing visible hanging or leaking. I proceed with my trip. No poping sounds for about another 60-70 miles. Then it starts again. I put the tranny into neutral and rev the engine to 3K, (this has been the approximate rpms while traveling), no vibration/poping sounds for the next several miles. I'm assuming this would rule out the muffler. I had to stop for fuel once, again no noises for the next 60 or so miles. My speed varied from 70-80, it seemed not to make a difference.
Any ideas?

Marks88

engatwork · #2 10-01-2002, 06:53 AM

First thought that comes to mind is 1/2 shafts. Second thought is the flex disc at the differential.

How many miles are on the car? Both jobs are pretty straight forward diy'ers. Once the job is complete it will be along time before you have to worry about it again.

Marks88 · #3 10-01-2002, 07:37 AM

engatwork,

210 k on the car. How does one check about the half shafts? I mean, what goes bad with them? I'll do a archieves search, but can you give me an idea what I'm looking for? Thanks for your quick response.

Marks88

engatwork · #4 10-01-2002, 08:49 AM

First thing to do is put it on jackstands and climb underneath. Look all around between the differential and the wheels. If the boots are leaking you will see evidence of moisture on the underside of the car in the vicinity of the boots. I have seen one so bad you could take the "shaft" part of the 1/2 shaft and move it back and forth about an inch or so. Also, you may NOT see any leakage and they may be bad. Again, look for "play" in the shaft part. I guess since it "broke" while you were driving you have to fix it

.

Marks88 · #5 10-02-2002, 06:45 AM

Udate,

Finally got a chance to take a good look under the vehicle. Not pretty.

Dirvers side differential boot almost torn off. Passengers side boots ok but cracking badly. Can anyone tell me how much lateral(from differential to wheel hub) movement or play in the axle is allowable. Drivers side axle seems snug, but the other side has about 3/4 to 1" movement, as all 4 wheels are on level ground. As I was moving the axle back and forth it was making the same sound I heard as I was driving.
Engatwork's diagnosis of half shafts was right on the money.
Also, has anyone done the boot replacement thing? How difficult is that for a DIY'er of average ability? I appreciate any input.

Marks88

engatwork · #6 10-02-2002, 07:53 AM

I would just replace both of them. I have seen pricing for rebuilts from $90/side to over $200/side. I would suspect that you would get to replace the $90 again sooner than the $250/side ones. They can run cracked for many, many miles as long as they are not leaking. They should not have 3/4-1" of play in them.

Nate Stanley · #7 10-07-2002, 10:52 AM

Just last week I had the same problem on my 300D Turbo.
It has the original shafts (256K), and my tech repored ruptured boots on the right side axle about 3 months ago.

Last Tuesday the EXACT same noise started, just as yours did, after about 40 minutes of constant highway driving.
Stopping briefly and resuming speed would make the noise go away.

After thinking about it for awhile, I figured out why it happens.

Unlike many CV joints that use grease, MB uses a heavy oil in theirs. So, the boot starts leaking, oil gets slung out past a critical point, and then as you go for extended distances at high speeds, the remaining oil in the boot is slung against the inside of the boot by centrifugal force. The shaft joint runs dry, and the noise begins.

Stop moving, and the oil falls back onto the joint assy enough to lubricate it again, and the noise goes away.

Since my boots are both intact except for a radial tear where the clamp attaches the boot around the axle shaft, this weekend I clamped a vinyl tube on the end of my grease gun, and shot about 100 strokes into each boot.

Came to work this morning on my usual 60 mile commute route, and NO NOISE !

I know this is only a stopgap measure, and I will order a shaft this week, bit if your boot is relatively intact, this may get you down the road until you can get a shaft ordered and installed.

Marks88 · #8 10-07-2002, 09:49 PM

Nate,

Thanks for your response. After finally getting a chance to take a long look at the axles, I decided to replace both, with one boot nearly torn off of one axle and a lot of lateral movement between differential and hub in the other, and 210K on the clock. I thought is best to do the switch-r-roo. The axles came in today. (Thanks for the fast service from PartsShop. Phil is the man.) I went for the rebuilds. Kinda leary about doing the work myself, but it looks pretty staight forward. I have the Haynes manual, and all the experience of this great forum.

How could I go wrong?

Marks88

engatwork · #9 10-08-2002, 06:54 AM

Changing 1/2 shafts, in my opinion, is one of the more straight forward jobs there are for a diy'er. Put the rear of the car on jack stands, jack up the rear differential and remove the rear most diff support, jack up the differential as high as it will go, remove the bolt from the center of the wheel hub and drive the axle out of the wheel hub with a brass drift. Lower the differential, remove the rear cover, pull the "clips" that hold the 1/2 shafts in and remove the half shafts after jacking the differential back up. The brake calipers have to be removed from the wheel for the 1/2 shafts to clear. Make sure to transfer the "shims" that are located at the differential end of the 1/2 shafts to the new shafts. Install the new shafts into the differential, install the clips, line up the 1/2 shafts at the wheel end and lower the differential. The 1/2 shafts should line up with the splined section at the wheel hub and slid in a little. You may need to use another jack to raise the wheels control arm to bring the hub up some to help get the shaft going into the hole. Once the shaft is in the wheel at the hub you should be able to install the bolt and tighten the 1/2 shaft at the wheel end. Doing it yourself allows you to inspect the diff internals. Make sure you clean the differential vent while you have the cover off. Seal, tighten the cover, bolt everything back together, let the sealant set up as recommended, fill it and drive.

Marks88 · #10 10-13-2002, 09:50 PM

Thanks All,

Thanks to all that contributed helpful info and guidance to my post. I was a little uneasy about replacing the half shafts on the 83 300 CD. Got the job done this weekend.

About 5 hours, but it didn't seem that long at all. For anyone considering doing this job yourself, it is a 5 out of 10 for the average DIY'er. Thanks again for the help.

Marks88

#11 10-15-2002, 11:25 AM

Nothing seriously worrying me but when I go above 70-80mph I get a slight rumbling noise. Sounds like it is coming from the rear of the drivetrain. Could this be a bearing? Thanks.