Darn driveshaft vibration - PeachParts Mercedes-Benz Forum

phantoms · #1 09-19-2004, 08:51 PM

Did a ton of maintenance items on my 300CD this Saturday. Drained and refilled the trans (and torque conv) and differential along with quite a few other things. I also replace the driveshaft flex discs front and rear, the center support and bearing as they all needed it. Now I have a vibration when taking off hard or after about 60mph. Car was smooth as silk before. Painted the driveshaft halves before removal and put it back in on the paint marks. Today (Sunday), took it back up to work and put it on the rack. Reaching up from underneath I can work the throttle by pushing on the linkage where it comes out the firewall. I rev it up and run it through the gears and can see no vibration at all in the driveshaft, but it I rest my hand on the small crossmember I can feel it somewhat (None on the center support bearing). So I wonder if maybe I missed by a spline (which I was sure I hadn't. Marks still line up, but I take it apart and try it one spline off both ways and vibration changes just a hint but it's still there. I take the flex disc off and change them around (front one to rear, rear one to front) and no difference. I have a 85 and notice that the factory marks do not line up (off about 8 splines) even though the shaft is in the same place it was before disassembly (as per my paint marks). Had to leave it at that as I had plans I had to leave for. Tomorrow I plan on working late to once again rearrange the splines, this time using the factory marks, and see if it makes a difference. I have a suspicion that it's a center support bearing problem (even though it's new) and want to rule out everything else first. I can really feel it through my seat when I get on it from a stop (at about 15-25 is when it vibrates really bad) and at cruise over 60 mph.

whunter · #2 09-19-2004, 09:28 PM

your center bearing is the problem, the bearing is out of balance with the shaft.
Pull the shaft and send it out for balance.
Some of the center bearings are coming from India, Pakistan and Turkey.

:Big Shock: There are quality issues.

You can try moving it 90 each time and hope this fixes the problem enough to live with.

engatwork · #3 09-19-2004, 09:29 PM

phantoms

Look real close at the pic and notice where I have made arrows to the original factory markings. Notice the "tit" on the lower section and the forged in arrow on the top section.

Look for pics here.driveshaft discussion

There may be a driveshaft repair facility in Savannah - I'm not sure. Anyway, the one I use which I can't recommend highly enough is Drive Line Service of Atanta - 404-361-0475.

phantoms · #4 09-19-2004, 09:37 PM

Jim, I made paint marks and used them when reassembling. The shaft has factory lineup marks also. There are two protrusions on the center yoke and a small protrusion on the front driveshaft hex (right next to the spline nut). These factory marks are what are off (as they were before dissasembly).

Whunter, that was my thinking, but I want to make sure first.

psfred · #5 09-19-2004, 09:46 PM

Make sure that the center bearing is pushed on straight with no crud holding it crooked, and "settle" the carrier before tightening the bolts. If you have the carrier off center, you will get some "orbiting" of the driveshaft at certain speeds and under load.

Also, did you replace the rubber carrier? If not, I suggest doing that, too, they go bad and allow the bearing and driveshaft to move too much.

Peter

phantoms · #6 09-19-2004, 11:18 PM

I replaced the carrier (the rubber was in bad shape) along with the flex disc (had a couple small cracks in them). Pressed the new bearing into the new center support, installed the flex disc on the driveshaft halves, mounted the front half on the trans yoke loosely, slide the rear half into the splines making sure to keep my paint marks aligned and then mounted the rear flex disc loosely. Install the two bolts for the center support, but didn't run them all the way down. Tightened the front and back flex disc. Rotated the driveshaft a few times and then tightened the spline nut. Tightened the center support bolts making sure that it went up evenly.

d.delano · #7 09-20-2004, 10:39 AM

So how does the car drive now

franklyspeaking · #8 09-20-2004, 10:49 AM

The 15 to 25 mph vibration is consistent with a bad or weak rubber center bearing support. I had this problem on my car and changing the rubber solved my problem.

Good luck.

R Leo · #9 09-20-2004, 11:07 AM

Apparently, even Mercedes-Benz™ had persistent issues with driveline vibrations. Somewhere, I came across a repair procedure for isolating/solving vibrations; basically, if the driveshaft would balance out on the bench, the procedure had the tech starting at the front flexdisk, marking the alignment, disconnecting it, rotating the driveshaft 120°, reassembling and test driving. If the vibration persisted the procedure had them rotating the shaft an additonal 120°. If the vibration continued, the tech was to rotate the shaft on to the original position and repeat the procedure on the rear flex disk.

I don't know whatintheheck you are suppoed to do if that doesn't solve it...

FWIW, I still have various vibrations in my driveline. There's the buzz in 3-4th gear from 1800 to 2000 rpm and, there's a faint hetrodyning wah-wah-wah at 65-75mph as well as the low rumble that comes and goes if you travel at speed over an undulating road surface.

The buzz, I'm convinced, will go away with a tranny replacement/rebuild. The wah-wahs are probably something that rotating the flexdisk/driveshaft relationship will cure and the rumble well, that's anyone's guess. I don't fret too much because the it's has been there well over 20k miles and is no better or worse.

kamil · #10 09-20-2004, 02:26 PM

I just had a problem where I thought that my driveshaft was making noise as well. It felt like I just swerved off the highway and was hitting the little grooves. I was working on my transmission mount and did not install it correctly. I'm not sure if you ever took it off for better clearance but if you did make sure you recheck it all.

phantoms · #11 09-20-2004, 09:42 PM

I had replaced the trans mount a few weeks ago. I didn't unbolt it to do the shaft which I've had in and out the car about 10 times now. Tonight I took it loose after work. Set it on the factory marks. I noticed if I rotated the front driveshaft by hand while the rest was out, I heard a little squeaking. I know that the original flex disc had words (in german) indicating which side to face the driveshaft. However, the replacement flex disc dosen't have this. Since I heard a squeaking (very small noise), I removed the front half and flipped the flex disc over (squeaking gone). Anyway, on the way home tonight, the vibration is a lot less, but it's still there. Can feel it lightly between 25 and 35 and from about 65 on up. If I get on it hard (I don't usually drive it like this) taking off it's much worse to about 35. I'm thinking maybe the center U-joint as I wobbled the spline-yoke around while it was out Saturday and could feel small indents. Couldn't really feel them tonight and assume that maybe the rollers rolled to a different position or something. I can run it through the gears while it's on the rack and not notice a vibration at all now. Seems like it's got to be under a load to do it.

R Leo · #12 09-21-2004, 08:37 AM

Quote:

Originally Posted by phantoms

I wobbled the spline-yoke around while it was out Saturday and could feel small indents.

That indent is where the joint has been sitting for the last 200,000+ miles. It is a 'loose' spot in the arc of the u-joint's movement caused by wear. You'll feel it under acceleration sometimes and at some point near cruise speed (65-75mph) as a steady vibration.

Quote:

I can run it through the gears while it's on the rack and not notice a vibration at all now. Seems like it's got to be under a load to do it.

Absolutely! No load and the shaft won't try and twist out of alignment because of excessive clearances at the universal.