Author Topic: Rear Axle Adjustment with Cross Arm Rubber Replacement  (Read 402 times)

LWB250

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Rear Axle Adjustment with Cross Arm Rubber Replacement
« on: January 19, 2019, 10:30:53 AM »
As a part of the freshening of the 1965 200SEb I have all new rubber bits for the rear axle. This includes, swing arm bushings, mounts, cross arm rubber buffers, etc., etc.

I'm wondering if when I replace the cross arm rubber parts as long as I return everything to the original positions as far as adjusting nuts I would be OK with the axle centering?

Thanks!

Dan

Aaron H

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Re: Rear Axle Adjustment with Cross Arm Rubber Replacement
« Reply #1 on: January 20, 2019, 08:43:13 PM »
Yes.  Just count the threads on the inside part of the cross arm adjuster before you  loosen the nut.  The nut on the outer part where the bushings are is to be run down until it stops.  The actual later adjustment is done on the inside part mentioned above.  Do this job with the rear springs out for ease of operations, and make sure that you renew your mount in the trunk.  Also take note of the long tubular bushing that mounts at the bottom of the arm that comes from the trunk.  This bushing is usually damaged 99% of the time.  The bushing itself isn't all that expensive at $150-$200, but replacing it involves removing the rear axle from the car....or at least lowering it enough for the trunk arm to clear the car. This arm also has a position it has to be put into, but this adjustment can be done with a straight edge and a ruler.  If this bushing is bad the car will wonder in the rear and cause the rear tires to wear funny.   

LWB250

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Re: Rear Axle Adjustment with Cross Arm Rubber Replacement
« Reply #2 on: March 01, 2019, 06:41:26 PM »
Aaron,

How difficult is it to replace the bushing? That is, with the bolt removed from the end of the pin it pivots on, is it likely the bushing will just come off, or will it require some force to remove? Or will it come off with the arm when the arm is removed?

I'm slowly accumulating all of the rubber bits for the rear axle, and just got the tubular bushing in a load of parts today. I was looking through the service manual and found nothing about R&R for it.

One of the MB clubs in Germany have offered a stiffer mount in the trunk that they had made as a group buy for their club, and they're selling the extras. I was wondering if that might be a good idea, as the cost is similar to the stock mount?

Thanks,

Dan

Aaron H

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Re: Rear Axle Adjustment with Cross Arm Rubber Replacement
« Reply #3 on: March 02, 2019, 10:02:10 AM »
Dan, if the axle is lowered enough for the trunk mounted arm to clear the car, then after removal of the large cap bolt on the end of the tube and flange that holds the pinion seal the arm should slide off of the metal tube.  However, the rear axle pretty much has to come out of the car to do this job.  You'll need the slotted socket to remove the pinon gear flange slotted nut, and you'll need a new crushing sleeve to reset the pinion to ring gear lash. 

After the metal trunk arm is removed from the rear axle, only then can the tubular bushing be removed and replaced.  This bushing also has a particular set position it must be in.  While the arm is off, you might as well renew the rubber boot between the axle halves.....but with a solid one.  You'll be opening a can of worms doing this job, but it's necessary all these years later. You won't regret it!  :) 

The job that instructs how to renew the tubular bushing will not be in the regular maintenance manual book.  This job is in the big 3 volume set....a set that took me 15 years to find all three volumes of.  However, I'm certain that the information can be found online.  I've never look, as I detest online repair manuals. 

The measurement you're interested in is distance "a" depicted in the picture below.  As you can see, the job is involved, and isn't easy or simple.  However, if you're comfortable with your aptitudes then go for it!  :) 

Edit......the cast iron mounting arm that goes up in to the trunk MUST be at a 90 degree right angle relative to the left side axle tube when taking the above measurements. This is done with the rear axle assembly sitting on a flat and level surface.  Otherwise the set up will be skewed.


« Last Edit: March 02, 2019, 10:08:15 AM by Aaron H »

LWB250

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Re: Rear Axle Adjustment with Cross Arm Rubber Replacement
« Reply #4 on: March 02, 2019, 09:24:25 PM »
Yikes! pulling the pinion gear flange? Yeah, I think this will get set aside for completion well into the future. I'm certainly capable of doing this, but it's a pretty substantial job, probably more than I want to take on any time soon.

So I can't just unbolt the cap bolt and slide the tubular bushing off of the rod?

And your thoughts about the stiffer upper mount for the metal arm?

Thanks!

Dan

drew56cus

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Re: Rear Axle Adjustment with Cross Arm Rubber Replacement
« Reply #5 on: March 03, 2019, 05:55:46 AM »
Hmm Aaron, I kidded myself once that i could do the pinion seal on the diff. I needed a special allen key for the drain plug, then a special tool for the pinion, and so on. Every step in the manual had me stumped. I decided it was best left to someone who had all the special tools and experience as it seemed beyond me. I don't regret that decision...
I remember fighting with those rubber bushes on the adjustable horizontal locating arm - new ones are about 3 times the thickness of the old ones, so i could not compress them enough to get the nut started. I remember trying big vice grips and clamps to try to help me. I can't remember what ended up working for me - does anyone else have any tips?
Cheers, Drew
A few W111 and W112 projects...

LWB250

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Re: Rear Axle Adjustment with Cross Arm Rubber Replacement
« Reply #6 on: March 03, 2019, 06:51:24 AM »
Hmm Aaron, I kidded myself once that i could do the pinion seal on the diff. I needed a special allen key for the drain plug, then a special tool for the pinion, and so on. Every step in the manual had me stumped. I decided it was best left to someone who had all the special tools and experience as it seemed beyond me. I don't regret that decision...
I remember fighting with those rubber bushes on the adjustable horizontal locating arm - new ones are about 3 times the thickness of the old ones, so i could not compress them enough to get the nut started. I remember trying big vice grips and clamps to try to help me. I can't remember what ended up working for me - does anyone else have any tips?
Cheers, Drew

Thanks for mentioning that, Drew!  I've got a set of those bushings waiting to be installed. It's way down the list of things to do, but at least now I know what to expect and will hopefully have a solution once someone responds to your question.

Dan

Aaron H

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Re: Rear Axle Adjustment with Cross Arm Rubber Replacement
« Reply #7 on: March 03, 2019, 07:32:19 PM »
Yikes! pulling the pinion gear flange? Yeah, I think this will get set aside for completion well into the future. I'm certainly capable of doing this, but it's a pretty substantial job, probably more than I want to take on any time soon.

So I can't just unbolt the cap bolt and slide the tubular bushing off of the rod?

And your thoughts about the stiffer upper mount for the metal arm?

Thanks!

Dan

Dan, look closely at your rear axle again.  You'll see that the flange that holds the pinion seal in has to come off before the arm and bushing can slide off.  In order to do this, the pinion flange that the driveshaft connects to must come off......which means the special slotted socket must be procured, and backlash reset afterward with a new crush sleeve. 

No comment on the stiffer upper bushing.  A 220se engine doesn't put out enough torque or horsepower to merit a stiffer bushing, and I can't imagine it making the car ride any better.  A stiffer bushing may help with lessening body squat upon acceleration, but again, the M-127 isn't powerful enough to cause a problem like that.  I'm guessing that's why the W112, W100, and W109 cars had different/stiffer bushings in this location.....because they offered higher torque and horsepower output. 

LWB250

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Re: Rear Axle Adjustment with Cross Arm Rubber Replacement
« Reply #8 on: March 03, 2019, 08:23:57 PM »
Thanks, Aaron, I was studying the rear axle construction and design this afternoon after i posted that and saw what you are now describing.

I haven't seen any indication that the cylindrical bushing is worn or damaged, so I may just be overthinking this whole thing. However, the question did come up as to how to compress the rubber bumpers/bushings to get the catering rod back together?

Dan

Cam

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Re: Rear Axle Adjustment with Cross Arm Rubber Replacement
« Reply #9 on: March 19, 2019, 08:43:31 PM »
I replaced the trunk bush, the lower support arm bush near the pinion, the pinion seal, the front and rear trailing arm bushes in the car on my w111 230s. It was a very difficult job to say the least, but I did it on my own, under the car..... I must have been mad/crazy
W111 230s 1966, cream, black interior.
W111 220se coupe,1961, black,red interior
W108 280s/8 1969 white, navy interior, column shift manual.

LWB250

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Re: Rear Axle Adjustment with Cross Arm Rubber Replacement
« Reply #10 on: May 03, 2019, 12:09:39 PM »
Cam,

You are most certainly not insane.

Last night I removed the pinion seal cover, centering link and support arm, all without dropping the differential out of the car. I didnít even have to lower it substantially or disconnect anything such as brake lines. Donít ask me how, but Iíll have pictures this weekend.

I was able to pull the sleeve out of the support arm and off of the pivot rod once everything got loosened. As expected, the rubber inside the sleeve was pretty much nonexistent. After that, I removed the mount in the trunk from the support arm. I was just moving it around when I realized I could tip the support arm back far enough to slide it off of the pivot rod. Wooo-hooo!

Iím busy cleaning everything right now, but expect to start reassembly tomorrow, which Iíll document in detail and post on my blog.

The key here will be the ability to reassemble the support arm in frame. Hereís how Iím planning to do it:

Heat support arm in oven at 200 F for several hours to expand the sleeve area by a few thousandths of an inch.

Place support arm back into position on the pivot rod with top in the trunk opening where the mount is located.

Press new bushing onto pivot rod/into support arm.

Reassemble remaining components.

Hope this works. Iíll know in another day....

Dan

LWB250

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Re: Rear Axle Adjustment with Cross Arm Rubber Replacement
« Reply #11 on: May 04, 2019, 07:38:45 PM »
Rear axle and all related rubber bits have been replaced and are in operation. Last thing I have to do are the trailing arm bushings, which I'll do in a couple of weeks.

No problem getting everything reassembled, even the centering rod and bushings. Putting some upward pressure on the differential gave me enough to get the nut started on the end of the rod.

Did a short test drive to let everything settle and get the center bearing carrier where it needs to be before tightening it up. Tomorrow I'll take it for a drive when I go to bust some clays at my sporting clays range. Gotta reward myself after all this work...

Dan