W108 Intermediate Driveshaft Support Question...

[nhdoc]

I'm chasing down a vibration that I have under load and underway at highway speeds in my '72 280SEL 4.5.

I've read about the intermediate support being a likely culprit in addition to the front flex joint. The front joint looks fine and all the bolt are tight but there is some play in the rubber "donut" surrounding the intermediate bearing which allows me to move the driveshaft up and down and around 1/8"-1/4". I think I know the answer already but will ask anyway...could this be the source of my vibration? Is there supposed to be any play at all between the rubber donut and the bearing or is it supposed to be a tight press-fit?

Thanks in advance...

[Tomguy]

I'd assume some play is acceptable (why it's rubber) but NOT 1/4". Replace that "donut". Was the flex disc done (or removed) recently? If the driveshaft wasn't placed back in the right position it could cause vibration. When you take the bushing out for replacement, check the condition of the bearing, if it's loose it will DEFINETLY cause vibration.

[nhdoc]

Originally Posted by Tomguy

I'd assume some play is acceptable (why it's rubber) but NOT 1/4". Replace that "donut". Was the flex disc done (or removed) recently? If the driveshaft wasn't placed back in the right position it could cause vibration. When you take the bushing out for replacement, check the condition of the bearing, if it's loose it will DEFINETLY cause vibration.

The tranny was replaced about 6K miles ago (in '04) and so was the tranny mount. I don't think the flex joint was replaced but looking at it it doesn't look too old and appears to be in good shape. I didn't do the work myself so I don't know if care was taken to mark the parts and keep them together properly or not.

I guess I will start with the donut and see if that helps. I can move the shaft around and when I do there is a gap developing between the bearing and the donut so it looks like the rubber has compressed some and maybe that's the problem...fingers crossed.

[alabbasi]

I had a similar problem on my BMW once which turned out to be a prop shaft doughnut (or as some people call it , a flex disc).

[nhdoc]

Originally Posted by alabbasi

I had a similar problem on my BMW once which turned out to be a prop shaft doughnut (or as some people call it , a flex disc).

The flex disc is the rubber disc with 6 bolts that go through it and attaches the tranny to the front of the driveshaft (on the W108 there is only 1, some models have one at the rear too). The donut I am referring to is the rubber mount between the intermediate bearing and the intermediate mount. I don't think the flex disc is usually called a donut.

[alabbasi]

In England it is When people talked flex disk, i had no idea what they're talking about until I saw a picture.

[nhdoc]

Well, since I practically have to remove the flex disc to replace the donut on the intermediate shaft I might as well replace it too since I can buy the febi part for under $50. That way I eliminate two possible sources of vibration at once.

[Tomguy]

Al: He means the rubber "donut" mount.

http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=108057&M=116%2E980&CT=F&cat=232&SID=41&SGR=001&SGN=01

part #146 in question.

[Shab]

I replaced the tranny mount & the flex disk at the same time on my 280SE 4.5 and it didn't make a darn bit of differnce on that highway speed vibration in my case. Never did figure it out before I sold the car. Motor mounts and subframes were also done prior.

Rear diff / shafts maybe? Drive shaft just out of balance? Transmission tired? Beats me, drove me nuts though. No joy on my buddy's 69' 280SE 111 doing same.

[Arthur Dalton]

Commonly overlooked vibration faults on swing axles are trans output shaft flange nut loose and worn rear diff hanger mount in trunk.

[nhdoc]

Originally Posted by Arthur Dalton

Commonly overlooked vibration faults on swing axles are trans output shaft flange nut loose and worn rear diff hanger mount in trunk.

Thanks Arthur...I'll check into those...would they cause a "shudder" like vibration under heavy load at low engine RPM?

also, by the trans output flange nut do you mean the 6 nuts on the flex disc or is there a specific nut which holds the flange to the transmssion output shaft itself? I took the car down off the lift so I can't see what exactly you are referring to at this moment.

[Arthur Dalton]

The nut holds the rear flange onto the trans output shaft.. They should always be checked when changing the flex disc.....It requires a pin wrench socket.

http://www.sls-hh-catalogue.de/bin/dbframes.phtml?mid=IN02

go to English, then trans. insert , then to item #57

[nhdoc]

Originally Posted by Arthur Dalton

The nut holds the rear flange onto the trans output shaft.. They should always be checked when changing the flex disc.....It requires a pin wrench socket.

http://www.sls-hh-catalogue.de/bin/dbframes.phtml?mid=IN02

go to English, then trans. insert , then to item #57

I see it, thanks, I will check that too. Since the tranny was replaced I know they messed with that so it is a great place to start looking!

Do you happen to know which tool I would need:

http://www.samstagsales.com/mercedes.htm#transmission

[Arthur Dalton]

Two different tools , depending on trans.

You may just want to go over to see Dean at Towne Lyne Motors..he may just let you borrow one if you mention my name.
I will be back up ther next week to do some work at the Pasta Loft.

[nhdoc]

Originally Posted by Arthur Dalton

Two different tools , depending on trans.

You may just want to go over to see Dean at Towne Lyne Motors..he may just let you borrow one if you mention my name.
I will be back up ther next week to do some work at the Pasta Loft.

I am not familiar with Towne Lyne Motors...let me know where it is and I will go by in my 280 and see if he can help me out.

You're in Florida but are coming up to NH next week?

Thanks.