Author Topic: Noises and Vibrations in the Drive Train (Read 7776 times)

Pawel66 · « **on:** August 23, 2015, 22:18:53 »

Gentlemen,

As I am walking through the issues related to my restored 280SL following the order of "from critical (cannot drive the car) to secondary", now I wanted to kindly request your advise on drive train vibration and noises.

1. Noise - high tone sound heard when torque is applied to drive train; silent when gas pedal released
2. Vibration on 3rd gear between, say, 40 to 50 km/h (25 - 30mph) when accelerating or slowing down

I did went through TM and posts. There were some similar issues flagged, but I could not get a clear answer out of the posts...

The flex disc, all bearings etc. are new. The shaft was balanced and assembled properly. U-joints seem to be ok.

Any hints? Particularly with regard to the noise.

I suppose for vibration I have to double check the disc installation and drive shaft balancing, etc., but the noise - I am not sure. The differential gears looked intact. From the posts I read - is it the rear axle geometry? Please kindly advise.

Best regards,
Pawel

Cees Klumper · « **Reply #1 on:** August 23, 2015, 22:42:53 »

When I had a vibration issue in a previous rear-wheel drive car, I put the car on jackstands and put it in first gear with engine running. Then I held a chalk to the driveshaft, to see if maybe it was not exactly centered. It turned out to be the cause. I adjusted the fit of the driveshaft until it was perfectly centered, checking every time with the chalk, and the vibration was gone.

As to the noise, I suppose it could be the gearbox or differential.

Pawel66 · « **Reply #2 on:** August 23, 2015, 23:13:35 »

Yes, thank you - I have read about the chalk exercise while doing my homework - not sure yours or somebody else's. A British car involved, if I recall correctly...

Thanks - this exercise may follow...

I think we can hear the sound in the rear more than from the gearbox vicinity. If it is a differential - would it mean the gears are gone?

mbzse · « **Reply #3 on:** August 24, 2015, 08:51:45 »

Quote from: Cees Klumper

.../...I adjusted the fit of the driveshaft until it was perfectly centered../..

Cees, I do not follow you here...? The front of the drive shaft tube is centered on the pin via a fitting; at the rear (towards the diff) there is a flange (with four "ears") which goes inside the machined seat in the diff flange. In addition, the flange has four holes for fitted special M8 screws). How to adjust centering...?
/Hans in Sweden
.

Cees Klumper · « **Reply #4 on:** August 24, 2015, 10:57:05 »

Hi Hans - I've just described what I did on another car (indeed Pawel, it was on my Triumph Spitfire), I haven't compared to how the Pagoda is constructed. I still think checking whether the drive shaft is perfectly centered is a good idea to diagnose the vibration, although it sounds from your description it's not a likely cause. My own Pagoda also had a vibration at approx 50 MPH although a PO had installed a new drive shaft, but that vibration was very minor and seems to have slowly disappeared over my years of ownership.
Other cause could be the wheels (balancing, out of round).

stickandrudderman · « **Reply #5 on:** August 24, 2015, 11:04:02 »

There is a centering bush in the front of the propshaft that often fails and causes a vibration.
The noise sounds like differential whine if you can play it in and out on the throttle.

Pawel66 · « **Reply #6 on:** August 28, 2015, 21:43:03 »

Well, stickandrudderman, seems to me you are getting me there!!! What you describe is exactly what is happening. Now: which one is the centering bush - please kindly look at the picture and maybe point, if you were so kind...

My mechanic did a number of Pontons, Adenauers, 300 SC coupe etc.. He got a rate of 1,1 by a German judge. But Pagoda he did not do before and we are struggling there a bit...

On shaft balancing - this is the primary thing to do, certainly. There are services available who do it on the car rather than on dismantled shaft and I will exercise this, so I will definitely follow Cees' lead.

Benz Dr. · « **Reply #7 on:** August 29, 2015, 02:23:04 »

Looks like you would need no. 32 which is the cross joint. Are you keeping the front end of your drive shaft well greased? Joint failure is often a result of running this part dry.

Pawel66 · « **Reply #8 on:** August 29, 2015, 17:33:03 »

Thank you! Looks like I need to look at it and there should be no play anywhere, including bolts.
As for greasing - hard to say what previous owners did. I am aware of the importance so now we will see to it.
Tanks for voice!

stickandrudderman · « **Reply #9 on:** August 31, 2015, 11:33:44 »

You MAY need item 32 if items 34,36,38 and 40 are worn to such an extent that they have damaged item 32.

Pawel66 · « **Reply #10 on:** August 31, 2015, 12:39:36 »

Many thanks again! I did order 32, centering flange, as well, as I thought if bushing assembly is worn, this one may be too. Not extremely expensive and worth fixing as we will have the shaft out anyway. Just to eliminate this end of the shaft

J. Huber · « **Reply #11 on:** August 31, 2015, 23:29:09 »

Not sure if you identified the noise yet but I wanted to mention this thread:

It is pretty self-explanatory -- not to spoil the ending but in my case it was a very simple fix...

http://www.sl113.org/forums/index.php?topic=11557.msg77493#msg77493

Pawel66 · « **Reply #12 on:** September 06, 2015, 10:01:36 »

Thank you!

I wish it were this kind of story!!!

Yes, the car will be inspected soon - it has just been put together, the nuts are marked with paint as per the tightening torque and actual tightening happening - but the human factor is always there and it might be that some nuts or bolts arelose!

Tomnistuff · « **Reply #13 on:** September 06, 2015, 21:31:54 »

Quote from: Pawel66 on August 28, 2015, 21:43:03

On shaft balancing - this is the primary thing to do, certainly. There are services available who do it on the car rather than on dismantled shaft and I will exercise this, so I will definitely follow Cees' lead.

Pawel66,
You can't leave us hanging with that incomplete statement.

There are numerous threads here that discuss the fact that people who say they can "Balance" a Pagoda driveshaft are MANY until they actually look at a Pagoda driveshaft, then they say, "I can't balance that thing. It won't fit any balancing machine I've ever seen."

If you know, I mean really "KNOW" someone who can and has balanced a Pagoda driveshaft, please identify them.

There are techniques for balancing dirive shafts on the car, that use the jackstands, the lift, the chalk, several hose clamps and quite a bit of time and trial and error - not much real science. There are videos on Youtube, but I don't know how well they work on a two piece Pagoda driveshaft, or where to locate the hose clamps. Mine is "by definition" unbalanced because I stupidly separated the two pieces before reading the part in the BBB that said to put alignment marks on the two pieces before separating them. That's somewhere near the statement that says, " Don't separate them."

I plan to interrogate everyone at PUB to find the answer to the problem, short of buying a new driveshaft, unless you have the answer.

Tom Kizer

stickandrudderman · « **Reply #14 on:** September 07, 2015, 15:47:45 »

Balancing the shaft should present no problem at all to a competent prop shop.

I have used an "on the car" service a couple of times but this was really to help locate the source of a vibration rather than rectify it.

Pawel66 · « **Reply #15 on:** September 07, 2015, 16:07:06 »

I will definitely come back on results - regardless of success or failure (even though "failure is not an option" as Ed Harris said in Apollo 13).

Yes, balancing is no problem at all and I will do it first. If the issue is still there - then I would be hoping for on car check to identify where it might be coming from. In the meantime I got the centering flange from MB (it comes as a set with bushing, spring, etc. in it) as well as the flex disc (also a repair set). This week or next I hope to do the exercise - I have to combine it with the overall check up after the first 800km after an engine overhaul, as manual suggests.

As for reassembling the shaft when we forget to mark the halfs (or marks came off or were painted over) - I guess it might be important how the U-joints are orientated vs. each other, then balance it and then mark. Very often there are marks on the shaft, not sure about Pagoda's shaft. Often if there is a mark on one half of the shaft, you point it against the greasing point. I am sure someone can help here, it is probably not that complicated. More important U-joints are tight and centered, splines are tight, etc.... I am afraid I am not qualified to give a responsible advise...

stickandrudderman · « **Reply #16 on:** September 07, 2015, 16:48:33 »

It IS important to get the joints correctly orientated, failure to do so will result in very rapid failure.
There is no mark other than the one you put there yourself before disassembly.........................

Pawel66 · « **Reply #17 on:** September 07, 2015, 18:05:04 »

A Dalton, thank you for your message. Could not send a thank you reply as your box is full...

Pawel66 · « **Reply #18 on:** September 07, 2015, 18:08:20 »

Stick, as I do not find a hint on U-joints orientation in Haynes (this is what I use) maybe you could drop a word on how they should be aligned?

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Author Topic: Noises and Vibrations in the Drive Train (Read 7776 times)