Maybe do a thorough visual inspection of the driveshaft and its components? Does the vibration go away if you are at highway speeds and drop it into neutral?
Maybe do a thorough visual inspection of the driveshaft and its components? Does the vibration go away if you are at highway speeds and drop it into neutral?
Blunder said:Maybe do a thorough visual inspection of the driveshaft and its components? Does the vibration go away if you are at highway speeds and drop it into neutral?
I'll have to think about it, and see if I can get it on a lift, I think the exhaust and heat shielding may cover it up some, but maybe it can still be looked at. Not sure about switching to neutral on the highway, but maybe I could give it a shot. Not entirely sure what it would tell me though, the driveshaft and transmission output shaft would still be spinning.
In reply to eastsideTim :
Maybe it wouldn't tell you anything. I was thinking maybe it would eliminate anything internally in the transmission as the culprit. I may be grasping at straws but I really want to see this get fixed and find out what the problem is.
I understand. I guess I've read too many threads on the Mercedes forums where even the dealership mechanics are just throwing parts at the problem because they can't diagnose it, either.
Kind of wondering if I should just hit the test and tune on Friday and send it hard down the quarter mile over and over, and see how it dies at higher speed for a few seconds. Of course, every drag strip I go to tends to have a rough enough surface at the end of the track that it'd be hard to tell if the vibration is an issue at 90+ MPH.
If it was me I would at least jack the car up and get under it and see if anything is obviously worn with the drive train. Grab the drive shaft and see if it has noticeable movement. Yank on the cv joints (if 4matic). Just generally wiggle any likely culprits around and see if something obvious sticks out to you.
Can the driveshaft be easily unbolted from the diff and rotated 90 or 180 degrees and bolted back up? I'm not sure how mercedes are made but my foxbody can have vibrations depending on the orientation of the driveshaft.
Driveshaft is a two piece unit, with giubos on both ends, and a carrier bearing in the middle. From my reading, you really don't want to try to re-index it. To get it out also requires partially dropping the exhaust. When we had it up on the lift initially, we couldn't see anything obvious. The carrier bearing, u joint, and front giubo are all obscured somewhat by the exhaust and heat shielding, though.
I think the rear CV joints were fine when we checked it. It's RWD.
I'm not sure if this would be considered safe or not due to no load being on the wheels but if it isn't unsafe maybe jack the rear end up off the ground and get the wheels up to the vibration speed. If the vibration is gone you could at least pin point it being in the front and if it's still there then it's coming from the driveline or rear wheels.
In reply to Blunder :
Might be worth a shot. Loads would be different without the wheels on the ground, but still might produce results. Would be nice to run it on a dyno.
eastsideTim said:Driveshaft is a two piece unit, with giubos on both ends, and a carrier bearing in the middle. From my reading, you really don't want to try to re-index it. To get it out also requires partially dropping the exhaust. When we had it up on the lift initially, we couldn't see anything obvious. The carrier bearing, u joint, and front giubo are all obscured somewhat by the exhaust and heat shielding, though.
I think the rear CV joints were fine when we checked it. It's RWD.
I've pulled my driveshaft many times and never paid attention to the orientation when I put it back in with no issues.
Well, that felt sketchy. Picked up a vibration around 50 MPH, it fell off fairly quickly, then was able to feel a vibration again around 70 MPH, but not as strong. Not sure if this confirms the issue is in the driveline or not, since wheels were in the air instead of on a dyno, so forces are going to be a bit different, and CV joints will be at a different than normal angle, but maybe it is something to go on.
Any ideas before I pull the car off stands?
Edit: Next few weeks of work are going to be pretty intense, so today is my last "easy" day to check on anything for a while. I'm starting to shop CPO V6 Camrys
In reply to eastsideTim :
If possible you could have maybe lowered the cars control arms on to cribbing so the angles would be accurate. At least it looks like you can eliminate anything being the problem in the front wheels or front suspension.
I'm not entirely certain it eliminates front end issues, but I am going to stop assuming that's where it is. Hopefully it can go back on a lift soon-ish for at least a more detailed visual inspection.
Was helping someone with their car tonight, so was already grungy when I got home, so decided to get the car up on cribbing blocks and do a little investigating underneath.
First check was the engine mounts. I did not see any hydraulic fluid leaking out of them, and really hadn't had a problem with excess vibration at idle, and I am assuming they are good for now, but may do a little more research on diagnosing them just in case. Transmission mount had not collapsed all the way, but based on a car wizard video, it has probably sagged a small amount. Maybe replace it just in case.
Front giubo was dirty, and somewhat obscured, but what I could see looked alright. Put that down as a maybe. Rear giubo had visible cracking at a distance.
And was much more obvious up close:
Not sure if it is bad enough to be the cause of vibrations, but looks like it should be replaced.
Could not see the center joint easily, since it is obscured by the exhaust and heat shielding. May go back out and check again when I am less tired, maybe grab the endoscopic camera.
So, I'll have to decide if it is worth attempting this work and spending the money and time, since it is still not guaranteed to fix the issue. U-joint could also be bad, and I'd likely farm replacing it to a driveshaft shop. Also, lowering the exhaust partly is probably going to have to be the way to go, as unbolting it from the manifolds may put other hardware at risk, since that appears to be the only rusty part of the car. Definitely not attempting this in my garage.
Oh yeah, one last picture of German engineering. Make a lightweight aluminum differential mount, then add lead weights:
Could you grab the driveshaft and give it a few yanks in different directions to see if anything is obviously wrong with it?
In reply to Blunder :
I'll have to do that next time I check under the car.
Sometimes I really hate having taken economics classes. Sunk cost fallacy is rearing its head. It'll cost about $600 for the driveshaft parts and the mounts, and that is if the u-joint is good. However, I don't want to tie up a lift while waiting on parts, especially if I can't guarantee it will fix the problem. Not to mention, anything I pour into this won't really affect the resale value much, if at all. So the money could be better spent on a different car that is more likely to be alright from the get go, not having turned into a project like this one has become.
There is also the thought that even if there vibration isn't cured, replacing the driveshaft giubos and center bearing (and maybe u-joint), along with other work that has been done, would probably resolve most of the serious safety risks.
With visible wear on the guibo I would be very very surprised if that wasn't the culprit here. Though most of my experience with that kind of thing is limited to old BMWs and that was a few years ago.
In reply to eastsideTim :
A couple of thoughts:
First, don't worry about tying up my lift. I got the left side welded in on the MiL's truck last night and I'm fixing to have the right side welded in tomorrow. I should have the rest of the stuff finished on it Sunday or early next week because the plan is for us to drive it back to them on Thursday evening. That'll open up the lift spot and if I wind up initiating The Other Project this weekend, it can sit on the trailer until we're good and ready. There's a rallycross on the 5th that I'll need the trailer for, but if I have to dump it and leave it at the storage lot, I've got a winch, so it's fine.
Second, I'm not sure that it's necessarily a serious safety risk. I know that things are different at 115 versus 80, but I'm feeling like the worst case is that the vibration gets progressively worse and causes us to have to abort the run versus causing a situation that could have you lose control of the car or have something come apart or come off. It's such a subtle feel even at 80 that I'm not getting the feeling like it's something imminent that's going to go pop on us. That said, having a failure that causes a DNF is still pretty bad, but I don't think it's likely that life and limb are at stake.
Of course, that Mustang looked pretty freaking sweet. And I bet a CX-50 would handle it no sweat :)
Was able to spend a few minutes in the garage tonight. Another look at the engine mounts, they still don't seem bad, so I am going to hold off on buying them. I put the transmission in neutral, so there would be a little bit of play in the driveshaft. No real movement front and back. I got into an angle where I could see the u-joint and center support, and I can't see any play in the u-joint. It also was dry, no leaking grease, so I am guessing it is good. The center support looked a little iffy, though. I was also able to push up on the driveshaft, and got some movement around the rubber part of the support, including what looked like a bit of separation from an inner metal part. It was only around 1/16" or so, but that probably should not be happening. Going to order a kit for the center support and giubos, and a transmission mount just in case. May also grab whatever is needed to change out the diff fluid, since it is probably original.
In reply to eastsideTim :
I can't wait to see if this fixes it. Fingers crossed.
Even if the lift isn't freed up next week (and I really think it should be), I should be able to get some time to come over and help out. The only thing I really have going on is getting the F150 ready to leave on Thursday afternoon.
Parts won't be in until next Friday, so I've got a little time. If I had thought about it, I would have taken the gear oil out of the order and tried to find some locally, since that is easy to deal with.
From a safety standpoint, I am feeling a little bit better if this turns out to be the source of the vibration. I've read multiple threads of people driving thousands of miles with the center support rubber pretty much destroyed. Like, they hear what sounds like the driveshaft hitting the floorboards, and they just keep going. One person had 1/2" of play in the center support. I would not be surprised if neglecting that is what helps kill the u-joint.
In reply to eastsideTim :
On the rusty manual Q45, the carrier bearing rubber was no longer attached to the metal mounting loop and it came out in pieces, and I didn't even feel it or know until I pulled the diff and the driveshaft just slid right out without unbolting the bearing support
In reply to Patrick :
Wow. That sounds like either an endorsement of how well balanced that driveshaft was, or how good the sound deadening was.
You'll need to log in to post.
