Driveshaft Vibration Cure
 

Well, after pulling the exhaust system a few times to get at the driveshaft and try different things, I have GREATLY reduced the drumming, thrumming vibration in my driveshaft. After going through all this, if I had it to do over again I think that I could have fixed it in fifteen minutes if I had known then, what I know now.

After pulling down the driveshaft, some time ago, to replace the front flex disk, I picked up the vibration. I had some tire problems at the time, so I didn't confirm the driveshaft vibration until I sorted out my tire problems which was a broken belt that was hard to find.

After the tire problems were taken care of, I thought that maybe I had not gotten the shaft splined up correctly, so I pulled the exhaust to check. I had indeed marked it and everything was cool. Since then I learned that there are permanent marks on the front and rear of the shaft from the factory, and they were indeed aligned properly.

I tried following some factory info, that said to unbolt and turn the shaft 120 degrees at the transmission and try it again. That did nothing. I then bought a transmission mount thinking that maybe it had come down some causing a bad angle. At the same time I got a carrier bearing and support and a rear flex disk. With all these parts on hand I was ready for the attack.

I got all these parts and pulled down the exhaust and shaft yesterday. The transmission mount was indeed much softer than the new one, and the rear flex disk was pretty cracked, so I put in the new parts. With the driveshaft out I was able to spin the carrier and evaluate it better than when in the car. It seemed in real good shape as did the support.

While the shaft was out, I rotated the u-joint on both axes. The joint had a "detent", or a notch in the center. It seems that it must be worn in that specific position in which this joint almost always stays. In these cars, the shaft probably never flexes over one degree, so the joint only wears in that specific spot. In fact, I really think that once you pull down the shaft, flexing the u-joint some 15 or 20 degrees, you might be causing something to happen inside those bearings because you are moving them out of their wear zone. Maybe this somehow causes the "detent" to occur.

I removed the harmonic weight while I had it apart, and before reassembling, I cleaned and greased the splines and the centering bushings and pins on both ends of the shaft.

I put everything back together and road tested. I could tell no difference.

With knowledge of the "detent" in the u-joint, I decided to move the carrier bearing position slightly to see if running the u-joint through a different arc might make it happy, and it did.

By taking loose the three 8mm screws on the converter heat shield and rotatiing it to remove, I had access to the carrier support. I loosened the vertical bolt on the drivers side and removed the one on the passengers side that is at an angle. I put a few washers between the carrier support and the chassis mounting hole, then put the bolt back in and tightened everything up.

After putting the heat shield back in, I was done. It took about fifteen minutes. I don't think the vibration is 100% corrected, but it is almost completely unnoticable.

There are two possible lessons here; the first, don't pull down the u-joint causing it to flex beyond it's normal angle unless absolutely necessary, secondly before going to all the trouble of removing the exhaust et al, try slightly changing the position of the carrier support to see if the vibration goes away. You can do it in fifteen minutes. It's worth a try.

I'm very relieved as I was beginning to think that I would have to buy the rear driveshaft portion for over $500. That's the only way to replace that u-joint. Given my recent career woes, that was not a very attractive alternative.

Sorry for the lengthy post, but I thought that it might help someone who is living with driveshaft "thrumming."

Have a great day,

Larry,

Persistent little sucker, aren't you. :D

Larry,

Thanks for posting this - that's pretty creative troubleshooting! I've had this problem with my 300E for awhile - eventually R&R'd the tranny mount, center support, and had the driveshaft bearings replaced, which has helped a lot, but the vibration isn't totally gone. Might try this at some point, depending on whether the vibration eventually gets worse again.

Incidentally, when the driveline shop was checking the driveshaft, they also found a "detent," or some resistance, in the bearings too.

larry which one of your cars were you working on?

Great Post Larry, I was going through the same procedure so many times that right now I can do the driveshaft with my eyes closed. I also started greasing the u-joint, even through everything flies preatty much right off it, some will always seek into cracks and help the shaft live longer.

I also did not hae any problems when bending the shaft further then it does while installed, if that creates a problem, I would say the bearings are worn out and should be replaced.

That driveshaft is one delicate piece of heavy duty metal :)

xp

Sorry, this was on my manual transmission 300E.

I guess my "detent" terminology did not adequately describe what the joint was doing. At the point where the shaft is virtually straight, it takes a little pressure on either axis to move the joint. Once past this pressure point, the joint is smooth as silk.

Have a great day,

what speed was the vibration?
 

Larry,

I also have a vibration I'm about to go after. What speeds / rpms were your vibrations most noticable?

Chuck

thanks for the clarification larry.ive got a vibration problem with my 90m 300 te 4matic and i suspect driveshaft alignment.im gonna give your method a try

Chuck,

MY vibration was at about 70 to 90 MPH. It was a droning or warbling, high frequency vibration. Tire vibration is MUCH more common and is at about a third the speed of driveshaft vibration.

If you're not sure if it is driveshaft or tire related, rotate tires and see if it feels different, if so it is tires, if not the next most likely possibility would be driveshaft.

That said, you need to think through a vibration before acting. If you kick it in neutral, does the vibration remain, if not it might be engine related. Does the vibration follow engine speed or vehicle speed?

Don't start doing things like I did without first determining that it is indeed driveshaft related.

Tires MUST be dynamically balanced on these cars. That means weights inboard and outboard on the wheels.

Good luck,

more vibration info....yuck - edit
 

Folks,

I moved my response to a new topic.

Chuck

1997 E320 vibration
 

Larry, I just read your post about vibration and how to determine where it might be coming from. My car has been vibrating at about 55 mph and just today I realized that it was engine rather than road speed that determined when I would have the vibration. I had my tires balanced to eliminate that possiblility. And, while they were out of balance, this did not solve the problem. Today I noticed by shifting into different gears that the vibration was occurring at about 1800 rpm regardless of which gear I was in. When cruising on the highway, I pushed the gearshift lever into neutral several times and the vibration seemed to stop. I feel that this indicates that the vibration must be coming through the engine. The last trip I took in this car I recorded 30 miles per gallon; so, I wouldn't think that the engine is out of tune. Is it possible that a spark plug, a wire, or some sensor may have gone bad since my good gas mileage? Any help would be appreciated. Thanks for any assistance, Big Ron

Big Ron,

You might want to get with an MB dealer and check the part number of your harmonic balancer. Some were recalled.

Good luck,

1997 E320's still had the M104 engine, so he wouldn't be affected by the harmonic balancer issue.

I would suggest having your motor mounts / transmission mounts looked at.

Do you get any sort of vibration at idle?

Vibration
 

I don't think it vibrates at idle but it seems a little rough when I give it the gas while sitting. This is our third car so I don't drive it much but I want to figure out what's wrong with it now, so I can fix it as soon as the weather warms up a little (really a lot). Thanks a lot, Big Ron

If you rev the engine to 1800 in neutral, do you get the (same) vibration as when the car is in gear at 1800 rpm?

Good Vibrations?
 

Larry,

Do you have each tire balanced on both sides?

I see it's a manual transmission (I'll trade ya :D). Have you checked rear trans bearing play with the trans in neutral? Just wondering if you have some play there, allowing slight vibration that increases as the speed does (differential bearing also is a suspect).

I have experienced this on other cars, such as hot-rods in the past with carrier bearings in the driveshaft, and it turned out to be the rear transmission bearing play. All that power hitting the rear bearing after dumping the clutch in a big block [383 magnum] dodge 4-speed:D.

Maybe this will help someone, even if it's not your current problem. Good luck with it! :)

I Know This Is An Old Topic
 

But, look at this for Volvo related driveline vibration problems and solutions. I did a search on transmission and pressure so I could get info on the broken spring problem and saw this thread.

http://www.brickboard.com/FAQ/700-900/Driveline.htm#DrivelineVibrationDiagnosis

Larry,
Would this fix also apply to an automatic transmission?

Yes, this would apply to an automatic driveshaft as well. If the problem is that the u-joint is worn in one spot, the shim between one side of the carrier bearing and the body will greatly reduce, if not eliminate the vibration.

Good luck,

U joint health determination
 

Larry/ Others,

I'm finally getting ready to pull my driveshaft. I tried Larry's suggestion and in my case it didn't work, so off to the next most likely culprit.

I have a new center bearing and flex disks if needed. How much "play" - rotational I would guess - would be acceptable in the u-joint? Are there other parameters to consider such as smoothness of operation in the bearings? The last u-joint I changed was on a '70 Torino 8).

Chuck

Chuck, unless you have a machine you can bolt the driveshaft into and balance I would use caution replacing the u-joint at home. It has to be "centered" in the yoke. As you will find it is pinned and not clipped like the Torino. I would recommend calling Earl at Drive Line Service of Atl (404) 361-0475 and arrange to ship it to him for rebuilding/balancing.

The u-joint is not servicable as most are. The driveshaft shops like the one Jim suggests, will put in an entirely new joint.

To answer your question about inspecting the joint, both axes should rotate smoothly. Most likely you will have a "notch" or detent as you flex the joint in both axes. This is what the relocation of the carrier will hide.

Since that didn't work, you should inspect the flex disks and the carrier bearing including its rubber mount. The front flex disk fails more often because it is subjected to lots of heat. The rear flex disk deals with no heat, so usually is okay.

Also when you remove the shaft to inspect it is common for it to slip apart into two pieces. There are marks that will show you how to realign. There is a raised knot on one piece that aligns with two raised knots on the other piece.

Good luck,

Thanks!
 

Folks,

Thanks again for your expertise!

I tried an interesting experiment of couple of weeks back to determine the source of vibration... but with no success. First was Larry's suggestion of offsetting the center bearing support, no-effect. Then I jacked the car up and then put it down on jack stands under the rear shock mounts. My theory was it would keep the axle half-shaft orientation closest to driving as opposed to having them droop downward.

The family was away so I had to try and look for the vibration alone. I first tested taking the car up to 50-55 on the jack stands. It had the vibration appear, but no sense of un-steadiness on the jack stands while running. I did have secondary jackstands and spare wheels under the body as well for backup.

Being alone I used a my camcorder to record front and rear driveshaft and each axle. Curiously there was no discernable vibration to be seen. It could be felt. The camera was about 3-4 feet away but I didn't see any vibration shown in any component. At over 260K now I expect it is worth trying center bearing and flex disks anyway.

I hope to have an update in a week or so.

Chuck

That is a good idea on putting the camera under there. I deal with rotating equipment and vibration analysis all the time and I would suggest using a stobe light set at the rpm of the d'shaft with that camera. We use strobe lights to inspect/check out rotating shafts and couplings all the time and I have to keep the thought in the back of my mind that just because what you see is sitting still - that baby is hauling. If there are driveshaft issues you will see them with the stobe light.

I just thought of this. Chuck, what exactly is it doing? If you are fine up to like, 40 mph, and then it starts vibrating then I would suspect the d'shaft. Otherwise, it may be something else. What are the symptoms?

Outstanding. There's nothing that substitutes for scientific analysis.

I would NOT just replace flex disks and carrier bearing components without first inspecting them. I realize that it is a pain to pull down the exhaust to accomplish this, but just throwing parts at the problem will most likely be a futile exercise.

Drop the driveshaft and rotate both axis of the u-joint. If they are not smooth, get a rear shaft or have u-joint replaced. Inspect flex disks at that time and rotate the carrier bearing to see that it is smooth and that the rubber is not tattered.

Good luck,

Just a thought though.

When you have your driving wheels off the ground, the drive line is unloaded for all practical purposes. This would change the behaviour of the system (for vibrations) compared to a loaded system like when you have the wheels on the gound and the vehicle is being driven.

Actually, due to the fact that the u-joints, flex disks and carrier bearing, when loaded, probably have slack taken up, in many cases, unloading the driveshaft would actually amplify the vibration, but not always.

Have a great day,

More thoughts
 

Thanks again for the inputs. I thought the load may make a difference as well. I actually contacted a local dyno to see if I could run the same experiment under load. I was thinking large mirrors and lights to see underneath..... haven't had the time yet so I decided to start with a few reasonable parts.

The symptoms are vibration starting around 40 up until 65-70 then it reduces. The vibration is felt in the center of the car. I have replaced tires and wheels and rotated several times in the last year and no change. Two separate, fairly competent shops have briefly looked at it with no conclusion - that was my hysterical differential post a while back. The camera did record a squealing sound starting around the same speeds... may again point to the u-joint. The mechanic may not have dropped the shield and the sound transferred back toward the differential.

I decided to start with cheap/simple and see how things progress. The offset center bearing was an easy try, but in this case it didn't improve things. As I said, I am at 260K plus now so a center bearing may be worth a try. While the shaft is down I am most interested in the u-joint as recommended. I think my SDL is fortunate in not having to remove the exhaust ( single all the way back). I got the shield off before without removing the exhaust, so I'm optimistic.

Any idea on the turn-around time for the Atlanta driveshaft guys. I've done more Mooresville - Atlanta and back in the same day trips than I can count. If they can fix it in 4-6 hours I may just drive it down ( in another car).

Thanks for all the assistance and I will certainly post any results.

Chuck

Yes, it's the 124 chassis that requires exhaust lowering for driveshaft access. It's not too tough to do this, but it's a real pain if you need access to the shaft more than once.

Without the exhaust in the way, it shouldn't be a big deal to pull the shaft as long as you have a way to safely raise the car.

Good luck,

Chuck
Call em at Drive Line Service and ask that question. It may be doable if you pre-arrange it.
I have always just dropped them off and then they UPS'd it back to me. The last one they did I dropped off on a Monday and had it back by Thursday.

update - finally
 

Folks,

I've been tied up lately and had a short commute, so not much progress on the vibration issue until this week. My master cylinder was failing (gee 260+K and things just fall apart 8^) ) , so I took the car to a local shop to fix. I had already purchased a new center bearing and flex disks getting ready to go after it myself. They were willing to look at it and use my parts. After the new parts were installed the vibration is 95% gone. They did detect a bit a wear in the u-joint, but not urgent. Thanks again for the advice and hope this helps some others.

Chuck