What happens when you ignore that "little" driveline vibration! - PeachParts Mercedes-Benz Forum

Mike D · #1 11-12-2007, 02:37 PM

Wonder if it woke up the driver? Someone actually was still driving this car after this occurred!

What happens when you ignore that "little" driveline vibration!-flexdisk01.jpg

What happens when you ignore that "little" driveline vibration!-flexdisk02.jpg

Adenauer · #2 11-12-2007, 02:38 PM

Is that the '71?? wow.

sjefke · #3 11-12-2007, 04:49 PM

I had that happen once in my '63 MGB. Front u-joint of driveshaft flew loose (circlip let go, followed by bearing, followed by yoke flipping out). LOTS of rattling that made me stop immediately! Some scrapes on inner side of tunnel and busted u-joint, that was all. Put a new U-joint in and all fixed. Overdesigned components are sometimes a good thing.

Bert

cth350 · #4 11-12-2007, 05:57 PM

The worst I've heard of is the drive shaft separating and trying to dig itself into the ground, which doesn't do much for the road, but does slow your car down quite a bit.

-CTH

Tomguy · #5 11-12-2007, 07:22 PM

There have been bad horror stories on this forum about what could happen with a torn flex disc. Imagine going at 80MPH when it tears completely. I would imagine your car becomes scrap metal at that point.

twinockchef · #6 11-12-2007, 07:44 PM

it amazes me how people will ignore what their car is telling them. I bet that driveline was talking up a storm before it happened.

sjefke · #7 11-13-2007, 10:50 AM

Quote:

Originally Posted by twinockchef

it amazes me how people will ignore what their car is telling them. I bet that driveline was talking up a storm before it happened.

Not necessarily. My driveshaft was fine without vibrations until at 50 mph it suddenly all let go. As long as the needle bearing was partially in place, it kept things together, but once it flew out, it started to vibrate and took just a few seconds for the yoke to work itself loose. The nice thing about MGBs is that they have a plate under the driveshaft which prevents the shaft from falling to the ground. It kept movement of the shaft to a minimum which really helps in avoiding bad damage. I guess they learned from their early racing days

Bert

OldPokey · #8 11-13-2007, 11:06 AM

When I worked for a tree company, the drivers would sometimes forget to disengage the PTO on the trucks before driving. Never mind that the PTO lever featured a humongous red knob and that we had installed the biggest red light we could find and set it up to flash insistently whenever the PTO was active. The PTO shaft is not balanced, and the usual result of a driver going too fast with PTO engaged was a thrown shaft - once it went right through the front of a Fiero, missing the driver by about six inches!

Mike D · #9 11-13-2007, 11:31 AM

The worst thing about this car is that someone had re-carpeted it and was in the process of restoring it! I bet they didn't even realize the driveshaft tunnel is an integral structural component on a unibody car.

Some peoples' kids!

twinockchef · #10 11-13-2007, 08:29 PM

If we are talking about the connection between the two shafts then it’s not that easy for the drive shaft to fail. Remember for the needle bearing to fall out. The intermediate driveshaft hold-down has to drop the two bolts that keep it in place. Up in till these two bolts fall out you will have noticeable vibrations right under your seat.
I could feel vibrations from my driveshaft and it's only problem was an old needle bearing and rubber bushing.
The most important point I am trying to get across it that with our older Mercedes we need to listen to them. Most things don't break without any warning.

Tomguy · #11 11-13-2007, 08:58 PM

Judging by the location, we're talking flex disc.

thorsen · #12 11-13-2007, 09:16 PM

Quote:

Originally Posted by sjefke

The nice thing about MGBs is that they have a plate under the driveshaft which prevents the shaft from falling to the ground. It kept movement of the shaft to a minimum which really helps in avoiding bad damage. I guess they learned from their early racing days

Bert

Bert,

When I was in college, I crested some RR tracks in my 1970 MGB and the rear U-joint decided to part company with the differential. I can't remember now if it was the 4 bolts had worked loose or if the joint had failed. The driveshaft wedged itself between the plate and the body so bad that I ended up getting towed the 2 hours back home.

Lesson learned. Even now, 15 years later, I press in the clutch whenever I cross RR tracks.

mercmad6.3 · #13 11-17-2007, 07:45 AM

it looks like a peice of the flex disc has flung around continuosly and dented the floor.It's impossible for a Mercedes Drive shaft to come off because the front is supported by a 30mm spigot ,the center is held in place by a center bearing and even if the bearing fails the housing holds it up.The rear is a universal joint ,and over the years i have never had to change on yet. if the engine were to move forward about 2 inches then perhaps the shaft might come off,but how often has that happened?...Never would be good guess.

Mike D · #14 11-17-2007, 08:18 AM

Dented? Dented? Hell, it cut the freakin' drive shaft tunnel almost completely apart!

I agree with your prognosis about the flex disk coming apart and whacking around. I just couldn't believe they simply covered the area with fresh carpeting and continued on their merry way.

It's scary to think what/who is out there on the road driving at highway speeds.

R Leo · #15 11-17-2007, 08:24 AM

Quote:

Originally Posted by mercmad6.3

It's impossible for a Mercedes Drive shaft to come off because the front is supported by a 30mm spigot ,the center is held in place by a center bearing and even if the bearing fails the housing holds it up.

Wanna place a bet on that?

The support bearing is pressed into place and basiacally just keeps the stub ends of the shafts aligned and isn't intended to contain the radial forces generated when a flex disk decides to take a hike.

The cut in that tunnel was made by the spider end of the stub shaft sawing it's way through like a skil saw.