Driveline Vibration - Page 2 - PeachParts Mercedes-Benz Forum

Diseasel300 · #16 02-27-2017, 11:27 PM

Yes, I'm well aware of the FSM procedures. My vehicle does not have a vibration damper, and the flex discs are properly aligned and facing the correct direction.

As stated above more than once: The vibration was present before servicing, and is still present afterwards. No change.

Zulfiqar · #17 02-28-2017, 11:41 AM

was the U joint notchy when you removed the D shaft?

SD Blue · #18 02-28-2017, 12:47 PM

Quote:

Originally Posted by Diseasel300

Yes, I'm well aware of the FSM procedures. My vehicle does not have a vibration damper, and the flex discs are properly aligned and facing the correct direction.

As stated above more than once: The vibration was present before servicing, and is still present afterwards. No change.

Outstanding! Just trying to help eliminate some of the things I ran across.

One thought, especially since you mention the vibration seems to be rearward. You might want to check your CV-joints. I didn't have cracked boots, at first, but extreme wear had caused a rumble from one and the only outward sign was an odd angle in the boot when the car was elevated. When I removed the axle for replacement, the wear was very evident.

Hope that helps in narrowing down the search. I know how frustrating it can be to chase down a drivetrain vibration.

BTW, if it's a route you want to take, there is a driveshaft shop in San Antonio that refurbishes the MB driveshafts. IIRC, it was about $300 for new u-joint, centering bushings, carrier bearing and mount, balancing and shipping.

Stevo · #19 02-28-2017, 12:48 PM

If indeed the DS was a little "notchy" one easy thing you might try is put a couple washers under one side of the center DS support, which will slightly change the ware points on the U joint.

Diseasel300 · #20 02-28-2017, 08:29 PM

Outwardly the CV joints appear to be ok. The boots are intact and there's no weird angles when the car is lifted. When the car was up on jackstands this past weekend, we rolled the wheels to check for runout on the CV's and they turned smooth and straight. Not saying they aren't the issue, but I'd suspect that the vibration from them would be similar to a wheel being out of balance since they rotate at the same speed as the wheels do. This vibration is much faster than that, which is why I'm suspecting the rather than the CV's.

The U-Joint wasn't "notchy" per-se, but it wasn't smooth and silky either. If anything the U-Joint is slightly on the "stiff" or "tight" side. Having not messed with a U-joint in decades, I don't remember what a "good" one feels like. With the DS parted, I could put the section with the U-Joint on a table, point the stub shaft in a direction and roll the DS on the table and the U-Joint wouldn't move. Too tight?

Dan Stokes · #21 03-01-2017, 09:22 AM

Quote:

Originally Posted by Diseasel300

Outwardly the CV joints appear to be ok. The boots are intact and there's no weird angles when the car is lifted. When the car was up on jackstands this past weekend, we rolled the wheels to check for runout on the CV's and they turned smooth and straight. Not saying they aren't the issue, but I'd suspect that the vibration from them would be similar to a wheel being out of balance since they rotate at the same speed as the wheels do. This vibration is much faster than that, which is why I'm suspecting the rather than the CV's.

The U-Joint wasn't "notchy" per-se, but it wasn't smooth and silky either. If anything the U-Joint is slightly on the "stiff" or "tight" side. Having not messed with a U-joint in decades, I don't remember what a "good" one feels like. With the DS parted, I could put the section with the U-Joint on a table, point the stub shaft in a direction and roll the DS on the table and the U-Joint wouldn't move. Too tight?

Depends on the age of the U-joint. Often when first installed they'll be tight but they should loosen up after a few miles of driving. A clue that most people miss - if the car "chirps" in reverse that's a bad U-joint. They'll make noise in reverse first because you're running the bearing backward from their usual direction of rotation so they speak to you. Of course, you CAN have a bad U-joint w/o that chirp but it's worth noting.

If you have the driveshaft out you can try manipulating the U-joint back and forth in either direction and see if you can pick up any roughness. And a U-joint isn't expensive or difficult to change so it's worth doing if only to scratch it off the list. Just take your time and make sure all the rollers are in place before you drive the bearing caps tight.

Probably once or twice a year I'll hear a car in a parking lot with the chirp and if I can flag 'em down I tell them. They always look at me like I'm a wizard - or a dunce.

Dan

Diseasel300 · #22 03-01-2017, 10:24 AM

This appears to be the factory driveshaft with a couple hundred thousand miles on it. No chirping here yet, but that doesn't mean much.

I had a U-Joint fail in a '96 Exploder with no warning. Went to back out in the morning, put the thing in reverse and heard a "clang". Put it back in park, had a roommate come out and look under the car when I put it in gear and he saw the whole DS jerk. Never gave any warnings, no noise, no vibration (although that car rode like a tank so you'd never notice anyway).

Unfortunately the Mercedes DS isn't one you can pop the caps and clips out and rebuild. Why they did that is beyond my comprehension, my brain has bled several times trying to understand the logic (or lack thereof) behind that decision.

I have the contact information for the DS shop in San Antonio from Sam (SD Blue) and I'll give them a call next week. At this point, I'd rather just cut my losses and swap the DS with one with a fresh rebuild. My time and sanity are becoming more valuable than the cost of the DS core!

86-300sdl · #23 03-01-2017, 11:09 AM

Quote:

Originally Posted by Diseasel300

This appears to be the factory driveshaft with a couple hundred thousand miles on it. No chirping here yet, but that doesn't mean much.

I had a U-Joint fail in a '96 Exploder with no warning. Went to back out in the morning, put the thing in reverse and heard a "clang". Put it back in park, had a roommate come out and look under the car when I put it in gear and he saw the whole DS jerk. Never gave any warnings, no noise, no vibration (although that car rode like a tank so you'd never notice anyway).

Unfortunately the Mercedes DS isn't one you can pop the caps and clips out and rebuild. Why they did that is beyond my comprehension, my brain has bled several times trying to understand the logic (or lack thereof) behind that decision.

I have the contact information for the DS shop in San Antonio from Sam (SD Blue) and I'll give them a call next week. At this point, I'd rather just cut my losses and swap the DS with one with a fresh rebuild. My time and sanity are becoming more valuable than the cost of the DS core!

There have been those that have DIY'd the Gen II W126 DS u-joint. I think it is an earlier ford part that fits. They've ground out the "staking" and punched them in and out, and with a chisel re-staked.

Although I've replaced many a u-joint it's the overall balance I was worried about and I can't diy that. Like you've said there's no DS balancer device on the Gen II W126 DS. Three bills is what it cost me too here in San Diego. Best three hundred I've spent on the SDL. Well....sort of lol.

Clemson88 · #24 03-01-2017, 02:30 PM

Reading through this thread and remembering the special treatment of the Gen I SD I recalled being instructed to assemble the carrier without tightening the bolts, lowering it to the ground and rolling the car back and forth to 'settle,' the assembly before tightening the big nut that holds the two shafts together and the carrier bolts.

I did that and my 84SD had no vibrations even with a well worn Transmission and differential mounts.

I'm just wondering if that special treatment is needed for the GenII cars.

Dan Stokes · #25 03-01-2017, 03:27 PM

Quote:

Originally Posted by Diseasel300

This appears to be the factory driveshaft with a couple hundred thousand miles on it. No chirping here yet, but that doesn't mean much.

I had a U-Joint fail in a '96 Exploder with no warning. Went to back out in the morning, put the thing in reverse and heard a "clang". Put it back in park, had a roommate come out and look under the car when I put it in gear and he saw the whole DS jerk. Never gave any warnings, no noise, no vibration (although that car rode like a tank so you'd never notice anyway).

Unfortunately the Mercedes DS isn't one you can pop the caps and clips out and rebuild. Why they did that is beyond my comprehension, my brain has bled several times trying to understand the logic (or lack thereof) behind that decision.

I have the contact information for the DS shop in San Antonio from Sam (SD Blue) and I'll give them a call next week. At this point, I'd rather just cut my losses and swap the DS with one with a fresh rebuild. My time and sanity are becoming more valuable than the cost of the DS core!

I've done a jillion U-joints over the years including the GM ones with the caps permanently glued in place. Those take oxy-actylene to heat 'till the goop runs out. My point - there's always a way. The worth of doing it at home, now that's another question.

I'm noted on here before that there are industrial balance companies that can balance the shaft in place. It's not free but isn't terribly expensive especially if you can get the car to a location they specify so they don't have travel time. People for some reason don't take advantage of this service and it's an amazing one. We used it many times at EPA to smooth out dyno shakes.

Dan

Zulfiqar · #26 03-01-2017, 04:41 PM

Quote:

Originally Posted by Dan Stokes

I've done a jillion U-joints over the years including the GM ones with the caps permanently glued in place. Those take oxy-actylene to heat 'till the goop runs out. My point - there's always a way. The worth of doing it at home, now that's another question.

I'm noted on here before that there are industrial balance companies that can balance the shaft in place. It's not free but isn't terribly expensive especially if you can get the car to a location they specify so they don't have travel time. People for some reason don't take advantage of this service and it's an amazing one. We used it many times at EPA to smooth out dyno shakes.

Dan

The GM joint caps are glued, Mercedes used a punch to create teeth that dont let the caps pop out. Its a bit obtuse. In some european countries I visited and saw some shops - they simply cut the joint out with a torch and smooth away two cap stakes, once a new joint is placed with lots of heavy grease in the needles they put the caps back as it was depth wise and stake them in.

These are taxi service cars and other usual lower spec models of MB, Im talking about steelies and hub cap edition W124, W210 etc.

On the BMW and Subaru forums they face the same issue too but are more DIY guys and most have just tacked a washer on the yoke where the caps are to lock the joint into place. Same issue of locked in U joint.

on the mercedes yoke no provision of an inner circlip or outer circlip is provided so at best a DIYer is really in a hole and has to pony up about 3 bills for a rebuilt shaft as no D shaft shop advertising amazing promises is able to take apart and rebalance a tripod ended shaft. I have visited about 8 shops in houston tx and all have the same story of we will get it shipped from San Antonio (which I can do without their markup in between)

If a machine shop can mill the factory yoke to provide inner circlip area future repairs can be a piece of cake.

ngarover · #27 03-01-2017, 05:58 PM

Hanger Bearing..... Also called the carrier bearing. That's where my money is...

Diseasel300 · #28 03-01-2017, 11:31 PM

Carrier bearing is brand new and was the reason for the DS pull in the first place. Made no difference.

Regarding the non-serviceable U-Joint - I'm sure there are plenty of ways to repair the U-Joint with some ingenuity and time and access to the correct equipment. My main issue is the lack of equipment or access to it. By the time I fiddled around with the U-Joint and had the DS balanced (and possibly ruined the DS in the process) I'd probably have paid for a replacement. Given the lack of suitable equipment and experience fiddling with U-Joints, I'll happily pay someone else who has both!

ffgb · #29 03-01-2017, 11:57 PM

What size washer fits? How many washers?
I would like to add washers and see if my vibration goes away and need to go to the hardware store first to purchase the washers.

Thanks

Stretch · #30 03-02-2017, 02:57 AM

The design of these propshafts and how they are fitted does not compare favourably with common driveshaft / propshaft knowledge.

(Let the lecture begin!)

This system relies on everything being in line - once you've got that idea fixed in your head the planets start to align and problems can be solved!

Think of an imaginary line that runs from the front of the engine at the crankshaft pulley that runs along the centre line of the crank through the centre of the flywheel - through the centre of the transmission - through the transmission yoke - through the flex discs - through the centre propshaft bearing - through the input yoke on the differential and out through the differential pinion...

...this imaginary line needs to be a straight line - it needs to be constant and unwavering in the vertical (y-axis) and the horizontal (x-axis) => this line needs to exist only in the z-axis (one dimensional)...

...the existence of a single universal joint is misleading. This needs to be set in the straight - zero degree - no bend position to stop any inherent induced vibrations. This configuration is less than ideal for a universal joint as it encourages "flattening" or Brinelling of the joint. All Mercedes UJs in this set up will end up being notchy.

The effects of a notchy UJ are amplified when this imaginary line - the alignment between each part of the driveline - is not just quite right.

The message is:

Consider the relative heights and positions of each resilient component of the driveline. Motor mounts at the front - transmission mount at the back - centre propshaft bearing - differential / subframe mounts at the rear. If one (or more) of these heights is not aligned with the others then you get a bend in the propshaft <= And in this system it should not happen!

(in addition to the resilient mounts flexdisc health is important)