W123 propeller shaft clamping nut loose? - PeachParts Mercedes-Benz Forum

biobenz617 · #1 10-09-2006, 06:22 PM

I'm in the process of replacing my flex discs while I'm there (replacing a rusted trailing arm is what started it all) and I've taken out the drive shaft. I somehow skipped the step of loosening the clamping nut while removing the drive shaft and was able to remove it nonetheless. Why does the service manual instruct to loosen this nut?? Does it clamp the splined connection together between the two propeller shaft halves and prevent them from moving or coming apart? if so, mine was loose before i started wrenching on the car

My splined connection fell apart while I was removing the whole shaft and luckily there are alignment marks on the two halves. I just hope that the service manual isn't lying when it says "On vehicles starting August 1982 the front and rear propeller shafts are pertinently identified." (41-050, 11) My car was manufactured November 1982

Old300D · #2 10-09-2006, 07:04 PM

If you loosen it, you can shorten the shaft length, making it easier to get it out of the way.

And I've never needed to mark the two pieces, as long as you align the flex discs when you fit it together. Same thing really, but I always forget to match-mark.

Stevo · #3 10-09-2006, 07:29 PM

I seem to remember the shop manual saying "after drive shaft work let the car down and roll it back and forth a little THEN jack it back up and tighten the shaft nut"

Should have a rubber "boot" covering the spline union.

I accidently pull one apart (78) and it wasn't marked

,had to replace the drive shaft

biobenz617 · #4 10-09-2006, 08:26 PM

Hmm, I guess mine was loose to begin with. We'll I made the cutoff by 2 months according to the shop manual. I'll see whether the driveshaft wobbles out of the car after I get everything back together

bgkast · #5 10-09-2006, 08:26 PM

When I did my drive shaft I never touched a clamping nut, of corse I was not following a shop manual though

. What does this nut do? When I put my shaft in I put in the rear section and tightened down the flex dist, then put in the front section and tightened down the front flex disk. Then I spun the drive shaft a bit and snugged down the carrier bearing bolts. Did I miss something?

Stevo · #6 10-09-2006, 10:30 PM

Quote:

Originally Posted by bgkast

When I did my drive shaft I never touched a clamping nut, of corse I was not following a shop manual though

. What does this nut do? When I put my shaft in I put in the rear section and tightened down the flex dist, then put in the front section and tightened down the front flex disk. Then I spun the drive shaft a bit and snugged down the carrier bearing bolts. Did I miss something?

The nut tightens down on the splines to hold the two halves together. I think its not out of the ordenary to find those nuts not tighten up . Just crawl under and if you can find a wrench to fit, tighten her up.

pawoSD · #7 10-09-2006, 11:08 PM

Quote:

Originally Posted by Stevo

The nut tightens down on the splines to hold the two halves together. I think its not out of the ordenary to find those nuts not tighten up . Just crawl under and if you can find a wrench to fit, tighten her up.

I had a vibration before, turned it over to the stealer, turns out that very nut was loose

He tightened it and the vibration has been gone ever since. (it was bad above 50-55mph)

Stevo · #8 10-09-2006, 11:36 PM

Quote:

Originally Posted by pawoSD

I had a vibration before, turned it over to the stealer, turns out that very nut was loose

He tightened it and the vibration has been gone ever since. (it was bad above 50-55mph)

Must be a matter of lose and looser, yours musta been "looser'

Wes Bender · #9 10-10-2006, 01:22 PM

As posted previously, the nut allows a slight adjustment in drive shaft length. The reason for rolling the car back and forth a bit before tightening the nut is so that the flex disks aren't subject to longitudinal strain. In theory you could leave the nut loose, but you would suffer spline wear, not to mention increased vibration.

Wes

biobenz617 · #10 10-25-2006, 11:41 PM

Quote:

Originally Posted by pawoSD

I had a vibration before, turned it over to the stealer, turns out that very nut was loose

He tightened it and the vibration has been gone ever since. (it was bad above 50-55mph)

I got everything back together last week and drove the car a bit to let the rear end seat itself in the new bushings before I tightened the nut (and I was waiting for my 2x 46mm combo wrenches from Northern Tool). At first I didn't notice anything, but about 20 miles into my drive to fill up on B20, I noticed that there is a vibration that started to appear around 35 mph and quickly dissapeared as I drove faster

I double checked the prop shaft alignment marks and they are dead on. Could the vibration really be from a loose clamping nut?? It wasn't vibrating before I did all the work.

Old300D, what do you mean about aligning the flex discs?

I think I might have to take it to the shop with my head hung no matter what, since the wrenches I got are about 2 feet long and basically require the car be up in the sky on a lift to use them. I quickly destroyed a sawzall blade trying to cut one in half.

biobenz617 · #11 10-26-2006, 11:19 AM

bump...

riethoven · #12 10-26-2006, 11:29 AM

Quote:

Originally Posted by biobenz617

I got everything back together last week and drove the car a bit to let the rear end seat itself in the new bushings before I tightened the nut (and I was waiting for my 2x 46mm combo wrenches from Northern Tool). At first I didn't notice anything, but about 20 miles into my drive to fill up on B20, I noticed that there is a vibration that started to appear around 35 mph and quickly dissapeared as I drove faster

I double checked the prop shaft alignment marks and they are dead on. Could the vibration really be from a loose clamping nut?? It wasn't vibrating before I did all the work.

Old300D, what do you mean about aligning the flex discs?

I think I might have to take it to the shop with my head hung no matter what, since the wrenches I got are about 2 feet long and basically require the car be up in the sky on a lift to use them. I quickly destroyed a sawzall blade trying to cut one in half.

Because the steel of the wrenches is hardened, you will have to grind on the wrenches to cut them down. Just use an angle grinder and have a bucket of water to quench it. Wear gloves, it will get hot.

biobenz617 · #13 10-26-2006, 11:47 PM

riethoven, thanks for the advice. I don't know why I didn't think of that earlier, but I did finally use a cut off wheel and made a stubby wrench.

I realized that only the clamping nut is 46mm and the prop shaft is smaller, but still too large for my adjustable wrenches. i just put her in park to hold the shaft still and worked on the nut. For some reason I thought the shop manual called for two 46mm wrenches. Anyone need a 46mm wrench for this same job?? I'll sell & ship my spare stubby wrench for $25. Just PM me.

Now for the road test. I drove around for a while and the vibration at 35 mph is gone now. Hopefully my job is done...

bgkast · #14 10-27-2006, 03:09 PM

Looks like I'll have to take mine to a mechanic too. I found the clamping nut, but I don't have anything big enough to get a grip on it with. That's a big nut!

Ken300D · #15 10-27-2006, 04:15 PM

I was able to tighten my driveshaft clamping nut with plain old sliding jaw adjustable pliars.

Ken300D