I've been reading about this procedure both on this forum and others and still have some questions.

1) I've read that's its possible to remove the dogbone without compressing the spring and without using a puller. At least one person claims that simply removing the nut that holds the guide rod to the LCA (the bolt is still trapped by the spring perch, of course) gives enough wiggle room to unscrew the dogbone. Anybody have any luck with this method?

2) I'm not sure I understand exactly what problem a puller/removing the above nut is supposed to solve. Is the dogbone simply too wide otherwise to unscrew without hitting the bottom of the car?

You will either need to move the LCA forward or remove the bolts holding the carrier to the bottom of the car. I found that supporting the LCA with a ratchet strap was necessary to relieve tension even with the adjustment screwed all of the way in.

There are 2 bushings that go into the top of each carrier. They were shot on one of my SDs and needed to be changed with the guide rod mount. I didn't replace them on the other SD but am thinking that I should have looked closer just because. One car is on stands until Spring when I'll reassemble. Change everything you can. It wil never be easier.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

So I only need to remove the 2 bolts holding the carrier (dogbone) to the car? You're saying that if I do this, then I DON'T need to move the LCA forward?

I had to move the LCA forward. I'd consider relieving pressure of the spring with a spring compressor if I had it. It was much easier to install the time I had the spring out. Regardless of how yo relieve pressure, you have to unbolt the carrier from the floor to clean the carrier push the new joint in. My indi said that he leaves the carrier installed but I ended up needing a press to get my new bushings in.

Spring removal wasn't necessary but moving the SLA Forward was. I used a ratchet strap that I use to hold a 4,000 lb sail boat on the trailer. You don't want the strap to break.

Perhaps it should go without saying but attach the strap to something solid on the car ie bumper. You don't want to pull the car off the stands by hitching to something external ie tre or parts car that sits in front of your work space. I didn't have a helper and used mechanical leverage instead of fighting.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

1) I've done this job on my W126 raised on jack stands using the FSM writeup for procedure #33-600.

http://www.startekinfo.com/StarTek/outside/12253/program/Chassis/33-600.pdf

You can do this job without compressing the spring and without using a puller.

2) The lower control arm gets in the way when you try to remove (or install) the 'dogbone'. But you can simply push it forward about an inch to get it out of the way (if you have a helper).

Some have used a come along winch with a strap to pull the lower control arm forward.

I've just used the OEM Bilstein jack wedged in horizontally into the wheel well to slowly move the lower control arm forward. It can't be too high up in the wheel well otherwise you can't turn the crank. I placed a piece of wood between the jack and wheel well to protect the undercoating.

Remember, safety first. Use wheel chocks, place your spare tire under the frame to support the car in case the jack stand fails, have someone within earshot, and wear safety glasses. Spraying the fasteners beforehand with thread penetrant (PB Blaster, etc.) makes for an easier job.

Good luck in tackling this job.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

Thanks for the info! But when you say the LCA is "in the way" of removing/installing the dogbone, do you mean the dogbone won't unscrew all the way off the guide rod with the LCA in it's resting position?

Yes, you can't completely unthread the guide rod (AKA Supporting Tube 49) from the 'dogbone' mounting point (AKA Supporting Joint 48) as the guide rod jams against the lower control arm. It "grows longer" as you unthread it and jams against the LCA.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

Ok, I'm a little challenged when it comes to visualizing this
I'm going to be spinning the dogbone off of the rod, correct? The rod basically remains stationary. It "grows longer" as more threads are exposed by spinning the dogbone off, is that what you mean?

Yes more threads are exposed, more pressure is put on the LCA and it gets harder and harder to unthread the ball joint (dogbone) from the guide rod.

Here is a numbered diagram of the assembly and dmorrison's invaluable DIY guide from 2004: DIY Bearing Bracket guide rod mount replacement for Mercedes Benz 300SD.. There are great photos of the parts and repair kits in Posts # 1 and # 10 of that thread.

You need to remove the bearing bracket (# 110) from the vehicle to remove and replace the ball joint (dogbone) # 120.

A) If the spring is removed (DANGEROUS PROCEDURE), you can remove the nut (# 107) and bolt (# 89) that hold the flat end of the guide rod (# 92), the rubber grommets (upper and lower), and metal grommet holders (upper and lower) (no #'s but part of repair kit # 146) in the recessed pocket of the LCA (# 77).

This would release the guide rod from the LCA and allow you to remove the whole bearing bracket (# 110) and guide rod a a unit. As a bonus you could then renew the parts that hold the guide rod in the LCA.

B) It may be possible to remove the nut (# 107) and push the bolt (# 89) out of the LCA with the spring in place, thus allowing the removal of the flat end of the guide rod AT GREAT PERSONAL RISK. This is just TOO DANGEROUS. The stored energy of the spring can be very dangerous. I would never do it. IT'S JUST TOO UNSAFE.

C) If you want to do it the FSM or dmorrison's way without removing the spring, then you have to unthread about three inches of the ball joint (dogbone) out of the tube end of the guide rod.

This allows you to remove the bearing bracket (# 110). However, the guide rod remains attached to the LCA. You have to pull the LCA forward while unthreading the ball joint from the guide rod. If you don't, everything will bind up.

Option C is the safest method by far.
Hopefully this unmuddied the waters a bit.

Attached Thumbnails

 

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

You can get at least an open wrench on the bolt head, It might help access if you remove the shock absorber. I wonder if loosening the bolt gives enough movement to where the carrier clears the frame without moving the LCA. If a quality spring compressor is a risk, Sixto and a come-along is a bigger risk

Sixto
83 300SD

I read a post on another forum where someone with a w126 gained the necessary clearance by simply removing that nut and washer and didn't have to fiddle with the LCA any further.
Is it just a matter of getting enough room to be able spin the carrier without the bottom of the car getting in the way?

Spinning the carrier will make quick work of it but anything you do to not have to move the LCA or deal with rusted perch bolts seems like a win to me.

Sixto
83 300SD

Of course I haven't tried Option B yet, nor will I for the forseeable future.

Just to be clear, are you meaning that after step 4, the bearing bracket (# 110) will be able to drop down low enough that there is enough room so you can spin the whole bearing bracket (# 110) without interference from the body?

If that is so, then there is no need to do step 5 or step 6 and that would be sweet.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

Don't over-analyze this. I've changed out the guide rod bearing mounts and the bushings in the bearing mounts, as well. There is no need for a spring compressor if you do a couple of things.

The spring needs to have a load, so I used ramps. I know some have sworn off the use of ramps but I'm not skinny enough to get under there far enough to work. Just be safe and don't take short-cuts.

As you mentioned, removing the "dog bone" bearing mount bolts. Mark the threads then you unscrew the guide rod bushing from the end of the guide rod.

Where a come-along comes into play is when you try to install the bolts for the bearing mount after the repair. I hooked one end to the LCA and the other towards the rear (I believe I used a large punch in the jack point for an anchor.

I haven't tried this but you might even be able to just use longer bolts, replacing them one-at-a-time, for the bearing mount. This may be just enough to pry the bearing mount down and replace the bushing. I doesn't take much to get enough clearance to unscrew the bolts holding the cover on the back side of the bushing. This might work if you don't have ramps or a come-along and need to support the wheel with an alternative.

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Sam

84 300SD 350K+ miles ( Blue Belle )

It's simple. Just take it apart, push the dog bone onto the shift then unscrew the bushing.

Putting it back together, is the reverse, use long bolts to reinsert the bushing into the dogbone.

First time I did it, I put bushing into dogbone and couldn't spin in place, had to take it all back apart. Goes smoothly if you use the right sequence.

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