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dmorrison · #1 03-31-2003, 01:01 AM

Well I was under the car today assesing the rear suspension rebuild.
In the 123 Service manual I reviewed the section on the coupled semi trailing arm rebuild. I realized that this was going to be quite a job. Your basically rebuilding two axel bearing assemblies per wheel hub and require some special tools. I figure out why they designed most of the tools so I could rig or make something to use instead. This morning I was looking at the wheel hub assembly and boy was I happy to realize that I did not have this on the 300TD.
I removed the dirt and coating of grease that had accumulated over the 22 years (81 build date) the car has been around, what a mess using the degreaser,the hose and a brush to clean everything.
Disconnected the rear brake lines and sway bar link. Took the caliper off and removed the rotor. Again cleaned more of the assembly again. The caliper and rotor were replaced about 25,000 mile ago and are fine along with the parking brake shoes etc.
Now on to the Hub bearings. I rotated the hub and felt for smoothness in the bearings. I think they are fine so I will not mess with them untill I have to.
I removed the leveling actuator ( called the spring strut in the manual, its what would be the shock absorber on a 123 sedan ). Boy what a mess with all the hydraulic fluid. I was amazed at all the dirt in the trailing arm section where the spring strut attaches. Again more cleaning.
I removed the Coil Spring, more dirt, and was able to get a feel on the weight of the trailing arm. It is actually pretty light. But you dont want it falling and hitting the wheel hub section or being damaged.
I place a floor jack under the trailing arm where the shock would attach. I have the car sitting on a 12 ton jack stands just behind the holes for the Mercedes jack that comes with the car. I proceeded to release the sub frame bushing bolts ( on the right side only, one side at a time). All three at once and removed the subframe bushing using a crow bar. It came out rather easily. The 123 does not have the top bushing that is shown in the service manual.
The movement of the subframe for those who want to know. I have the differential still attached at all the normal points. The right wheel hub has the sway bar link removed, the rotor off, the brake line removed and the caliper off. The coil spring and spring strut ( shock absorber) are also removed. The supporting points for the subframe in the wagon are the forward bushing and the rear differential mount. The top of the differential is bolted to the subframe. When I disconnected the items I have listed above the subframe did not really move at all. It dropped maybe 1/2-1 inch.
To get access to the outside trailing arm bushing I had to pull down on the front of the subframe and I actually shoved the old subframe bushing into the gap sideways. It seemed like a nice amount of gap. I was able to get a socket, a universal and an extension for the Pneumatic air hammer. I had to use the 500 Ft. Lb impact wrench to get the bolt for the outside trailing arm bushing to release. But you can not lower the trailing arm yet until the inner bushing is released
I was able to get the inside trailing arm bushing nut and bolt to release with the impact wrench also ( a 125 ft/lb unit). Then I ran across my first problem.
I could not remove the bolt to the inner bushing because the flex disk for the driveshaft is in the way. I now have to lower the driveshaft so that I can move the flexdisk out of the way to get the bolt out so I can lower the trailing arm to remove the bushing. Because of the offset of the driveshaft, the left side will not require the dropping of the driveshaft. Except it will already be done.
I am considering disconnecting the axel shafts to allow better cleaning and easier working on the trailing arm since I will then be able to remove it from the car. I also figure that if I have done that I might as well replace the axels since I'm half way there.
I'll keep posting to let you know how the job goes.

Wish me luck.

Dave