|
|
|
#1
|
||||
|
||||
Annoying vibration during acceleration
I have an '81 300 SD that gives off a rather harsh vibration while accelerating. You really feel it between 15 and 25 mph coming up through the floorboard and gas pedal. I was told by a Mercedes mechanic that it was a bad universal joint. It did remind me a lot of a similar problem in a BMW 325 which was indeed remedied with the installation of a new (rebuilt) driveshaft. I pulled the Mercedes driveshaft out and there seemed to be a notching effect in the universal -- that is, it would pop into a home base position which was straight ahead on both sides. Oh dear, one rebuilt driveshaft later, I still have the problem. I'm hoping it's not the tranny which seems pretty smooth all in all. Could it possibly be a bad torque converter? I have so little experience with automatics that I'm just guessing. I throw myself at the mercy of Mercedes master minds.
|
#2
|
|||
|
|||
Ask yourself this question. "Why does the noise come on at 15 and go away at 25". Is it because the transmision shifted into 2nd at 15 and 3rd at 25, then you likely have a transmission problem.
If you still have the driveshaft out start the car put it in gear and rev the engine SLOWLY from 0-40 mph see if there is any noise. This will require very little throttle without a drive shaft. Also note the RPM vibration occures at. DO NOT PUT THE CAR IN PARK UNTIL AFTER YOU SHUT OFF THE ENGINE or you will hear the load noise of a parking pawl trying to engadeg into a rotating parking plate. If you get vibration doing this test you have pretty much isolated the problem to the transmission. If you dont get vibration you have not yet eliminated the transmission. If you already have the drive shaft in the car try a road test using full throttle acceleration and followed by another using very light acceleration. This will cause the transmission to shift at different points. If the problem occures at the same speed all the time no matter what gear your in you have now isolated the problem to be something that follows wheel speed only. That would include somewhere from the output shaft of the transmision (unlikely) to the tires (somewhat likely, more likely if the problem occered at about 50 mph). Problems that are agrevated with speed and keep getting worse as speed increase are generally accociated with pure imbalance. Problems that get aggravated within a certain speed range are generally accociated with system stability issues and may be highly aggrevated with imbalance. It is unlikely the problem is in your wheels because the typical wheel and tire combination has dynamic stability issues in the 50 mph range. You appear to be well below that speed. But if the radail plys break down in the tire side walls the dynamics could change. The drive shaft on the other hand should have stability issues at a speed faster than the car can go unless something happened. Something that would change the drive shaft stability would be its mounting or a crack, and infact the transmission, engine and differential mounts could also come into play. The most likely components supporting the drive shaft that have been known to degrade are the drivechaft center bearing support or the rubber flex couplings. You may want to put the car up on jack stands and run it. If the problem will occure on the stands take a look at the wheels to see if they are obviously bouncing up and down. If not remove the wheels and install 3 standard bolts on each wheel to hold the rotors firmly in place. Run it again and see if you still have a problem. I will give you what I consider my most likely guess. And that is that your problem is most likely in the driveshaft center bearing support. John Roncallo |
#3
|
|||
|
|||
Sorry, have owned a tranny shop for 15 yrs.
Tranny's "DON"T" vibrate, never have seen one it will always be the shaft or mounts, etc: JKohn1 |
#4
|
|||
|
|||
Guess what, I have a 84 500SEL, 91 300D, and a friend has an 87 420SEL and another friend has an 88(?) 300E, and all have the exact same problem. Same speed, only when accelerating, and 1st or 2nd gear. I have learned to accept it as normal. If someone comes up with a fix, I would love to hear about it. By the way, my 84 500SEL has all new engine, trans, differential mounts, new flex disk and new center support mount and bearing, and rebuilt driveshaft.
__________________
84 500 SEL (307,xxx miles) |
#5
|
|||
|
|||
Is the vibration totally dependent on speed or is it also dependent on load?
Don't forget the drive axles. They are very susceptible to vibration under load from the CV joints if worn.
__________________
Steve Brotherton Continental Imports Gainesville FL Bosch Master, ASE Master, L1 33 years MB technician |
#6
|
|||
|
|||
same thing on mine... problem was that one of the pistons/cylinders wasn't being compressed correctly/enough. fixed now and runs smooth
|
#7
|
|||
|
|||
In hopes of finding this problem for my self and others I will give some more clues on my 84 500SEL. Remember, my 91 300D also does the same at the same speed, and under the same conditions.
I only feel the vibration at about 20 MPH. It comes and goes very quickley. It only happens at moderate to heavy acceleration. I don't feel it a light acceleration or WOT. At WOT, it passes 20 MPH so quickly that I really can't tell if it happens or not. Here are other facts to help. Following have been replaced 1. Used transmission from an 98 420SEL. 2. New flex disk front and rear. 3. New center support and bearing 3A. Rebuilt and balanced drive shaft. 4. Rebuilt axle shafts (two times) 5. New tires and different wheels. 6. New rear axle bearings. 7. New engine, trans and differential mounts. 8. Complete rebuilt front end. 9. New rotors and brakes all the way around. 10. And other things I can't think of right now. The above things were not done to fix this vibration, just part of a rebuild on a car with 250K miles. The car runs great, drives great, is smooth on the road with no vibrations. We just got back from a trip to Flordia with was about 1500 miles round trip, and averaged 21 MPG go 75 to 80 the whole trip.
__________________
84 500 SEL (307,xxx miles) |
#8
|
||||
|
||||
Annoying vibration during acceleration
Gentlemen,
Much thanks for you generous response to my question. Roncallo, your troubleshooting advice is something I should already know but it is very useful nonetheless. I've put the new (rebuilt) driveshaft in already and the center support bearing is new. I had a strong suspicion that it would be the problem also. Whoops -- no discernible improvement, but what do you expect for $500? Ouch. Am glad to hear the opinion that the tranny is likely not the problem. Too expensive right now. Paul McKechnie, in your first post you said your '84 500SEL has the same problem but in your second post you said that, after the numerous repairs, it ran great with no vibration. Did you mean no other vibrations than the one in question or did something you did solve the problem? I also installed new front and rear flex discs. My engine mounts should be replaced and I could imagine that weak mounts might allow an oscillation under certain torquing conditions. Since they need to be replaced anyway, I'll do that and see if it helps. Stevebfl, I don't notice it at all over about 30 mph -- I'm thinking it might be because the major torque and flexing involved in getting off the line taxes whatever the weakness is. On the other hand, I've noticed that it will persist to some degree even when I'm backing off the throttle at around 25 mph. Your thought on inspecting the drive axles is a good one, I think. The vibration seems to originate in the firewall area, but everything's connected of course so maybe the firewall is where the vibration finds a soundboard, as in guitar soundboard, so who knows. At any rate, it will take me a while to try all of these leads out and I'll post any good results I get. Thanks again. Carl McFarland 81 300 SD |
#9
|
|||
|
|||
Carl,
I'm sorry, I didn't make myself clear did I? What I should have said: After all the repairs and replacement of the parts "there was NO change in the 20MPH vibration". There is no vibration at any other speed. When driving down the road the car is smooth, with no vibrations. If I had to make my living trying to explain things in writing, I would have starved to death long ago.
__________________
84 500 SEL (307,xxx miles) |
#10
|
|||
|
|||
Guys, I'd like to re-open this thread.
I've had this exact acceleration-vibration problem on my '91 300SE for the last 8 years or so. Checked/replaced just about everything mentioned above in that time, but no change. Anyone got any new solutions/ideas? Tks DG |
#11
|
|||
|
|||
If it is only under a load I would check the cv axles to.(It kind of feels like a rumble.)
|
#12
|
|||
|
|||
Thanks. I kinda agree with you.
Yeah, it's a thump-thump-thump from the driveline, at approx 3x wheel speed. After going through engine mounts, tranny, driveshaft, etc; I feel pretty strongly it's not those. Maybe the u-joint, but it's fairly tight, and the fail mode for it seems to be a constant vibe at higher speed. I did reverse the axle shafts a few years ago, to see if I could notice a difference, but no change. Axles feel tight when flopping them around by hand, but that probably doesn't mean much. One thing I did notice; it goes away when the car is cold, the longer it's driven the more noticeable it becomes. Doesn't seem to have gotten much worse over the last 75k miles, so it's gotta be a slow wear issue, like a u-joint or CV joint. I thought it would get worse, then I could find it, or justify buying new axles just to try. Maybe I'll bite the bullet and pop new ones in, getting kinda tired of failure in locating the problem. DG |
#13
|
|||
|
|||
I had the same problem a few months back. I checked everything but could not find a fault. It wasn't until I pulled the transmission cross member off that I found the gearbox mount was fine but the actual alloy case on the box was cracked.
|
#14
|
|||
|
|||
Many cars with 2-piece drive shafts and center support bearings have drive shaft vibration issues. Other than the above mentioned things to look at also look at things like the bushings that hold the diff. including the one right at the front. also look at the sub-frame bushings. Every thing from the front of the car to the back needs to be attached nice and firmly and in a straight line. I've seen people have a-little luck fixing minor drive shaft vibrations by shimming the trans mount up or down or the front of the diff. up or down but never tried that myself.
|
#15
|
|||
|
|||
I have had the problem at about 40 mph. I started expermenting and on my car (the 84 500SEL) raising the rear of the tramsmission about 3/16" made it almost go away. You can also try lowering the center support by using washers, and changing the angle of the diff using washers. The center support and diff tricks didn't help mine at all, but it didn't hurt it any either, so they both went back to original. There is a procedure to allign the drive line but it requires special tools which I have never been able to find anywhere. Even the local dealer said they didn't have them. They just said to replace all mounts from front to rear and install a new driveshaft and that would fix the problem. I didn't wait for them to give me an estimate.
Paul
__________________
84 500 SEL (307,xxx miles) |
Bookmarks |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Funny sound and vibration at acceleration | lylemiller | Tech Help | 8 | 03-01-2003 10:24 PM |
Vibration during acceleration | curtsmb | Tech Help | 10 | 01-28-2003 02:12 PM |
260e Vibration During Acceleration | etsa | Tech Help | 3 | 08-20-2002 03:11 AM |
Acceleration Vibration | Austin814 | Tech Help | 0 | 05-07-2002 04:06 PM |
92 300D Vibration at Idle/Surge during acceleration | repoe3 | Diesel Discussion | 1 | 03-29-2001 01:20 PM |