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.

__________________
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?

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.

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

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.

__________________
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.

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.

__________________
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: http://www.peachparts.com/shopforum/diesel-discussion/92874-diy-bearing-bracket-guide-rod-mount-replacement-mercedes-benz-300sd.html. 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

 

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

Ah, I see why I didn't understand
What I'm referring to as the "dogbone" is part #110 above, while you're calling part#120 the dogbone. I'm calling part #120 the guide rod bushing.
Does that mean that part 120 can spin inside of part 110? Is this how the caster is adjusted? I thought the fit would be too tight for the bushing (ball joint) to be able to be turned inside the dogbone (bearing bracket).

Yes, the caster is adjusted by turning the shaft of the ball joint (#120) into or out of the guide rod (# 92).The fit is tight but it can be turned. On photo # 2 of post # 10 of dmorrison's thread, you can see the hexagonal hold (painted light green) on the threaded shaft of the ball joint (where you place your wrench).


To remove the bearing bracket (#110) you are essentially over-adjusting the caster (until the threaded shaft of the ball joint is finally free of the threaded end on the guide rod).

Remember to count and write down the number of exposed threads on the ball joint shaft before you wrench on it.

This gives you the rough caster setting for the new ball joint you will be installing later.

Also remember to install the washer (#128) and nut (#131) on the threaded shaft of the ball joint before threading it back into the guide rod. BTDT.


Happy wrenching.

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

I don't believe this to be an alternative because the OE bolt is too long to move clear of the guide rod with lower spring perch in place. I thought about cutting a hole in the spring perch to allow the bolt to go through but either or both the highly remote chance I'd do this job again on the same car and possibly the bolt is directly under the spring dissuaded me. But why is this alternative unsafe? If you unbolt the guide rod mount carrier (110) from the frame, the spring doesn't push the LCA away and break free. It takes tremendous force to move the LCA forward with a jack or come-along as it is.

Sixto
83 300SD

That's my thought as well: if you remove the bolts holding the carrier to the car (as recommended in the FSM), this is no different from loosening the guide rod bolt on the LCA as far as the spring is concerned.
My only worry is if I'll be able to get a wrench on the bolt head up top in order to loosen and tighten the nut below.

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?