Whinning sound - Low Oil Rear End

[Skitzerow]

I picked up my new (old) 1968 Pagoda sl a couple of weeks ago.  I wanted to drive it a little bit.  Drove it about 90 miles only to discover the following week that it only had less than a quart of oil in the differential case.

Now I have a little whinning sound, and am not quite sure how serious it is and how long I could go without major surgery on the rear end.

Anybody have this problem.

As an off-shoot.........I also can't find where to hook the vacuum tube from the distributor up to that is just hanging by the air filter area.

SDK

[hands_aus]

On my 250 sl this vacuum connection is under the venturi unit and is accessed from the mudguard side of the venturi.

How well does the car go, and what sort of economy are you getting, and is the car easy to start cold, given the vacuum hose is not connected?

Did you top up the diff oil?

Bob(Brisbane,Australia)

[Skitzerow]

I did top off the rear end with 80-140 differential oil.

The car took several revolutions to start the engine.  Especially when it was hot already.  But seems to be a little better with the vacuum hose hooked up.  Stills idles rough though.  Need to determine the problem there.

I have not checked the gas mileage yet, but I read these only get 17-19 miles per gallon.

I want to get rid of the whinning sound in the differential.  Sounds like it could be a worn bearing more than the gears themselves, because there is no slack in the gears.  The housing can act like a speaker cone in amplifying a worn bearing. Had the same thing happen with a washing machine years ago.  The washing machine sound like it was going to blast off.  Turned out to be a bearing that was amplified by the machine cabinet and transmission.  When the bearing was swapped the machine was as quite as could be.

SDK

[Ricardo]

You might try checking the diff. hanger mount, which is accessable in the trunk. These large rubber mounts have a dish shaped 4" dia. plate ontop of them and as the rubber gives out the plate/washer makes contact with the frame of the car and transmits diff. gear noise. Your diff. may be fine
Richard V

[hands_aus]

SDK,
I saw in the other post that you also had a vibration of the internal mirror at high speed.
This can be caused by hard rubber engine mounts giving metal to metal contact. Similarly with the rear diff mount as Richard mentions.
Replacing these mounts will change the feel and sounds of your car.

On the later cars a relay that operates for 2 seconds was provided on the start up relay circuit. It should operate every time the car is started hot OR cold. It was an option available for installation on the earlier cars.

In regard to your cars' idling. There was a very good discussion about this. It showed how to  adjust the linkages and air/fuel mix.

Have a look through the topics.

The Haynes manual and the MB service manual both have good inforamtion about these adjustments also.

Bob(Brisbane,Australia)

[Albert-230SL]

quote:Originally posted by Ricardo

You might try checking the diff. hanger mount, which is accessable in the trunk. These large rubber mounts have a dish shaped 4" dia. plate ontop of them and as the rubber gives out the plate/washer makes contact with the frame of the car and transmits diff. gear noise. Your diff. may be fine
Richard V

Hi Ricardo and all,

Is there any way to check that diff. hanger mount without to dismount it from the car?
I'm not sure about mine, because sometimes I hear some metallic noises or knocks (like spring noises or like the trunk were not well closed) from the back of the car. These noises mainly appears at low speed and over bumps, and even whith the neutral gear (so I guess they are not from the differential). I think these noises started when I changed the four shock absorbers, but I'm not 100% sure.
Could a wrong diff. hanger mount cause this kind of noises (perhaps damaged during the assembly of the shock absorbers?)? Any other idea?

Note: In spite of the noises, the handling and feeling of the car is really good with the 4 new Bilsteins!

Thanks in advance,

Albert de la Torre Chavalera
Barcelona (Catalunya/Spain)
Feb.'64 230 SL Euro 113042-10-002432

[rwmastel]

Not to stray from the SDK's differential/axle noise, but Albert's noise may be his exhaust.  There should be a flat plate across the top of the two tail pipes just rear of the muffler.  A rubber bumper should be mounted above this and putting pressure on it.  The theory is the rubber hangers keep upward tension on the exhaust to keep it tight against this rubber bumper.  Try moving your (cold!) tail pipe up/down and see if it bangs against anything.

Rodd
1966 230SL Euro
1994 E420

[George Davis]

Albert, the diff hanger mount can be inspected visually.  It is located in the trunk, centered on the forward crossmember, under a square plastic cover (some covers are missing).  Remove the cover and you'll see a square metal plate with four fixing screws, then a round plate above it, with a bolt in the center.

On a new/good mount, you will also see maybe 3-5 mm of rubber between the square plate and the round plate.  On a worn-out mount, the round plate will be touching, or very close to, the square plate.

The mount is very easy to replace.  Undo all of the screws and the center bolt, lift out the old mount and drop in the new.  It will probably be necessary to jack up the diff a little bit to engage the center bolt.

Shock absorbers can also contribute to noise; I think it has mostly to do with the hardness or softness of the rubber bushings.  I had KYB shocks with relatively hard bushings for a while, then installed Konis with softer rubber bushings.  The car is quieter with the Konis.  I don't know what the Bilstein bushings are like.

George Davis
'69 280 SL Euro manual

[Albert-230SL]

Thanks Rodd and George,

I tried moving the tail pipe (it was a good suggestion Rodd!), and it doesn't seem the cause of the noise. Next I will check the diff. hanger mount according to George's instructions.
Anyway, I noticed that right rear spring doesn't have its bottom spring rubber pad... maybe this could cause the noise?
About the shock absorbers, the previous ones also were Bilstein, so they should have similar rubber bushings... if they are the reason of the noise, I cannot understand why...

Thanks,

Albert de la Torre Chavalera
Barcelona (Catalunya/Spain)
Feb.'64 230 SL Euro 113042-10-002432

[Ray Ortiz]

if you have whining noise.....90 percent of the time is the axle rubber mounting.  To check it out:   Place a jack under the axle and jack it up then visualy check in the trunk, put downward pressure on the car, if the ruber moves up---(gives under pressure) you need to replace it.