Rear Comp Spring, Axle & Prop Shaft Alignment Prob

[jameshoward]

Hello,

Below, I explained how I replaced all the bushes on the rear suspension. Thanks to info on this site, I was mentally and physically prepared for the 32mm bolts at the rear of the trailing arms. They were trickey, but do-able.

I've just finished changing the rear trailing arm bushes and thought I'd offer a view on how it went should others want to give it a go. I also have the cut down sockets I used if anyone in the UK needs to borrow them (they're heavy and I'm in Europe; it would be cheaper to make your own if in N America I think).

You need all of the replacement parts. The metal parts are shown here:

 

This is just for one side. The rubbers are shown here, together with the old ones that came out:



The right hand larger rubber is the one that goes at the front of the arm where it joins the chasis (under that triangular piece of metal where most people put axel stands). The left hand piece, of which there are 2 per side (one either side of the metal tube shown in the above photo) is shown below one of the old pieces that I pulled. As you can see, there was a lot of wear on these old parts, but less wear on the forward bush (the right hand rubber).

I got all parts from SLS (www.sls-hh.de). The metal work was Euros 137 less tax (which I think is about one billion US dollars at current rates) and is set No 60 on the relevant (rear axel) SLS page (it comes with the 4 rubber bushes); the forward rubber bush is part no 70. and the rubbers were about 6 euros each. I also bought the bush shown on that page as part number 115.

The only tools you need are a good jack, 2 axel stands, a sodding great big wrench (we used a 4 ft torque wrench) and a 36mm cut down socket. You need a vice to press in the new bushes and a burner of some kind to burn out the old ones. You also need a socket set to remove the various smaller bolts. You will need a hammer to peen over the tab washers at the end, and a screw driver to bend them out of the way at the start. Having a friend to help is pretty essential. You will also need lots of cups of tea and a sense of humour. Here's what we did:

Having read up on the site what a truly difficult job removing the 36mm bolts could be, we sprayed the bolts and everything else we had to remove in duck oil for a few weeks to loosen things up. With the car over a pit, we used a long wrench (4ft) with a 36mm socket to loosen the large nuts. Big torque wrench and spanner:



We also loosened the 3 bolts holding on the tringular plate for the forward bush to be replaced. There is a larger (17mm I think) nut in the centre that also needs to come off.

With everything loose (one side at a time) we put the car on stands and then put the jack under the suspension arm. Having remove the forward plate and centre bolt, we slowly lowered the jack to remove the rear spring. (By far the easiest way to do it; to change the upper and lower spring rubbers we messed around with spring compressors - a complete waste of time). With the spring out (note which way is up) we removed the arm by removing the rear bolts. Here is a photo of the old bolts. As you can see the central sleeves were very pitted and corroded: 



There is a circlip that holds on the metal plate that can still be seen on the old sleeve. We had to burn out the old bush to get to the circlip which was very rusted.

With the arm now free we steam cleaned and sprayed it (it's aluminium and the spray job was purely cosmetic). We then pushed the new rubbers in, popped the plate on and secured it with a circlip. Shown here:



As you can see we had to invent a way to compress the bushes to get the plate and circlip on. In the end we just used a big washer with 2 strategicially placed bolts. It was pretty easy after we figured it out and drank tea. Here's the assembley:



We then pressed the new bush into the front of the arm and reassembled. Note that there was a lot of corrosion on the area where the front bush attaches. We had to remove a lot of rust and put a few coats of hammerite on to protect it.

This was the left side complete. On moving to the right side, there was a little surprise in store from MB. Amazingly, on my car at least, the trailing arms are in different positions. (I think it was something to do with the exhaust...) Anyway, we'd measured our required socket depth for the left side and gas axed and ground it to the correct level. However, it was way to deep to fit in on the right side (the outer/wheel side bolt was the problem). We had to lop off about another 6mm to get the socket in there. It's difficult to see from under the car until one trys to fit a spanner or socket, but the difference is very real as can be seen by the difference in the socket in these 2 photos which show the socket with about 10mm already removed for the left side, and then the socket with all but maybe 8mm remaining for the right side:






So if you want to make your own socket, make sure you take your measurements off the right side - you will need only the depth of the bolt head - about 8mm.

With that done, the right side went as for the left. In total I suppose that we could have done this in about 3 hours per side. It took more like 6 because we faffed around and decided to steam wash and paint bits. I'm not including the time we spent cutting the sockets down. Twice. In all, not a hard job really.

REAR ENGINE MOUNT/TRANSMISSION MOUNT

Since we had the car up on stands and I've had the part for ages, we decided to replace the rear engine/transmission mount. First, put the jack under the transmission (which sat on a block of wood) to take the weight of the transmission, etc. Then remove the forward heat shield, all the bolts around the plate that holds the mount and the mount bolt. Annoyingly, because my mount was so shot and because the large bolt that secures the mount to the plate simply span around doing nothing, we had to go in above the plate and remove the 2 mount securing bolts. It is fiddly, but takes only about 10 mins to do it that way. Here's a photo of the old mount; its easy to see here that the threaded metal centre of the mount had come away from the rubber and hence just turned as we attempted to undo the bolt:



This job took about 90 mins to do. It went far better than I thought it would.

Anyway, since that job, the suspension has been great. So much tighter. However, I was plagued by a vibration and squeak when going over bumps. Whilst touring with the car in France last week we finally discovered the source of the noise; the rear compensating spring (my nemesis) is up against the area to which the fuel tank affixes. This photo shows the problem:


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When looking in more detail at the position of my rear axle, I noticed that it seems to be slightly further to the right than to the left; i.e. it does not appear to be in the centre as more of the right tyre is visable than the left.

When greasing all 21 odd grease nipples yesterday and searching for the ones on the drive shaft in the middle of the car (that don't seem to be there on my car) I saw that the angle of the shaft looks like this.

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Can anyone please advise me on what I need to do? I think I need to move the axle foward to move the spring off the metal. I think I need to realign the axle, and I think therefore that I need to build that pipe contraption that I've read about. I haven't done a search on this yet, but if anyone has the specs and measurements I'd be grateful for them.

Finally, on my prop shaft in the second photo the small disk my point is indicating spins. Is this correct? (And where are my grease points???)

Grateful for any advice on the axel/comp spring issue.

James

[bpossel]

Hi James,

The only alignment of the rear is side to side.  All I can think of to ensure you are not hitting the comp spring is to make sure that all of your rubber is good.  New rear subframe mount rubber (trunk), new trailing arm rubber, etc.  If I would take a guess at the first thing to look at, it would be your trailing arm bushings.  These need to be good, and on correctly.

Here are a couple of pics of the alignment tool.  





Bob  

[jeffc280sl]

James,

Bob has provided infor on an alignment tool.  It is helpful when aligning the axle side to side using the cross strut and front to back using the two bolts on the base of main carrier adjustment at the "hinge pin" slider.

An alignment of the rear axle may help.  If not maybe you can adjust the gas tank a bit to clear the spring.

The center drive shaft carrier can be off slightly, like in your photo, because it floats in a large rubber ring.  Preferably it should be more centered and look the same at the left and right side bolts.  If I remeber correctly the small disk does spin.

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[mbzse]

quote:Originally posted by james
.../...Can anyone please advise me on what I need to do? I think I need to move the axle foward to move the spring off the metal. I think I need to realign the axle, and I think therefore that I need to build that pipe contraption that I've read about. I haven't done a search on this yet, but if anyone has the specs and measurements I'd be grateful for them.

I think you are on to the right path of correcting your car here, to move the diff forward.

The rear suspension geometry on our W113 (as well as W108, W111 and W112 cars) is quite intricate. To get all suspension parts positioned within spec is most important in order to enjoy a comfortable ride.

One part of this geometry is the position of the upright center carrier arm, measured along the front/rear axis of the car. If you look in the M-B Workshop manual (BBB) or the M-B Book of tables, section 35 Rear axle, there is a spec of 158mm +/- 1 mm (i.e. quite a tight tolerance) for the positioning of this carrier clamped on its rubber mount. This is measured from the flange of the propeller shaft on the diff over to the front of the carrier arm. Measurement "a" as seen in the image below:

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[Cees Klumper]

quote:Originally posted by bpossel

If I would take a guess at the first thing to look at, it would be your trailing arm bushings.  These need to be good, and on correctly.

On that point, that these bushings (look like flat donuts, or actuall more like hockey pucks with a hole) need to be in correctly, I remember doing these years ago and noting that they go on counter-untuitively, i.e. what looks to be wrong-side-up. Maybe double-check the good book and recall how you installed them. Good luck with the quest!

[ja17]

Hello James,

Try compressing and rotating the compensating spring it may have become bias to one direction over the years.

Later W113 cars did not have a grease fitting in the middle of the driveshaft.

A dab of silicone will keep that disc from spinning freely.

[jameshoward]

Gentlemen,

Thank you all for your advice, and Bob and Hans thanks for the pictures and measurements.

I've looked at the BBB and their section on axle alignment and I THINK I understand, but I've done a search on this site and there are a number of people, like me, who aren't entirely sure how to use Bob's alignment tool. So, for me, posterity and the sake of my misaligned axle, would someone mind explaining how the alignment frame should be employed? Am I correct in thinking that the two arms slot onto the two bolts that hold the front of the trailing arms (i.e. foward of the triangular plate held on by a further 3 bolts)? If that is correct, what is the point on the car with which/to which the fine pointer points to/connects to when the axle is correctly positioned? Also, and from the advice below I think I get it, to move my axle which seems grossly misaligned do I just loosen of the forward training arm bolts and 'nudge' the rear axle until it looks correct, or do I use the various methods of adjustment mentioned by Hans and Jeff? Also, Hans, I don't think I can achieve the tolerance of +/- 1mm on the upright support as one of the surfaces from which one is to measure is inside the boot/trunk is it not?

Joe, you are correct. My comp spring does indeed have a bias towards the rear of the car. I will try to turn it a little.

Many thanks thus far. I am quite looking foward to building Bob's device and once I know how to employ it properly will set to work.

James

[waqas]

Hi James,

The alignment tool confused me too at first. The drawing Bob posted is actually one that Arthur Dalton ("A Dalton" username) created and posted here some years ago. Bob has kindly clarified the dimensions in his figure.

The two longer arms slot onto the bolts that hold the front of the trailing arms (center bolt, which holds CENTER of the triangular plate). The shortest arm aligns the front-facing end of the hinge of the swing-axle, where the vertical carrier attaches to the axle. This end is of course a big bolt, so alignment is approximately to the center of this.

You can adjust the alignment by simply adjusting the lateral support rod that is affixed (through a pair of rubber bushings) to the inner right wheel well area. There are two nuts, as well as a threaded rod that need to be adjusted. The rod has a cast nut somewhere in the middle that can be used to turn the rod. This rod is quite pricey to replace so be careful and apply plenty of penetrant to break the nuts free.

The tool is nice to have, but you can also use a plumb line to mark the positions of the three points on your garage floor and then take the appropriate measurements.

[mbzse]

quote:Originally posted by jameshoward

Hans, I don't think I can achieve the tolerance of +/- 1mm on the upright support as one of the surfaces from which one is to measure is inside the boot/trunk is it not?

You most certainly have to take the rear axle down (off the car) to make this measuring and adjustment of the vertical support arm.

The support arm positioning needs to be performed after one has replaced the rubber mount bushing for the arm on the rear axle center swivel shaft (or disassembled these parts). See pic (courtesy Bob Possel):
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[bpossel]

Hi James,

Waqas is correct, this is Author Daltons tool.  What I did different is to screw the copper pipes together with small screws.  It was hard to lay under the car and hold this tool in place.  One modification to help with this would be to put a screw on each end that goes over the trailing arm bolts. Once the copper tube end is over (on) the bolt, tighten the screw to hold it there.  Make sure that your tools measurements are 877mm and 280mm, center to center, respectfully.

The end with the "pointer", note: I used a small screw centered in the copper pipe endcap, is lined up with a "punch mark" on the bolt located on the end of the vertical carrier arm of the rear suspension.

Good luck,
Bob  

[ctaylor738]

Working on my W110.

On the question of the positioning of the rubber bushings at the front of the arm, the side marked with "UNTEN" faces down, according to my manual.  This is the side with the ridge molded into it, so the flat side goes against the underside of the car.