Steering box mounts on W123

Hey yall,

I have a 1983 300D with 68k miles on it that has had a clunk ever since I got it. I have replaced every single wear item in the front end. Upper control arms (ball joints and bushings). Lower control arm bushings. Tie rods, drag link, steering shock. Shocks. Idler arm bushing. Lower ball joints. Brake support mounts and bushings. All of this work got rid of most of the clunk, but if I move the wheel quickly right or left I still have a clunk.

BTW, my steering box mounts were a little loose (started turning at 40 lb-ft). I tightened them up to 60 lb-ft (upper limit of spec per CD). Are W123's prone to cracking where the box mounts like some older cars?

Any suggestions?

[jylee]

I have the some problem with my 75 240D, the steering gear box design is similar with the 123's. The frame where the gear box is mounted have some cracks and it was repaired. I have a body shop weld a small plate over the crack area, but it only lasted two years. At this time, I check and tighten all three bolts once a month. If the bottom bolt slip off the socket, I know the vibration have loosen the bolt too much, and I replace the bend bolt.

jack

[stevebfl]

The 123 chassis doesn't have the frame problem that the 114/115 chassis' did.

I suspect the problem is the coupling between the box and the steering shaft (between box and steering wheel).

BTW I have fixed many of the frame problems on 114/115 cars and placing a plate on the outside is not the answer. The frame in that area is a rectangualar tube about 6-8 inches tall and 3-4 inches thick. The heavy steering box is bolted to one side by bolts that tighten from the other side. If this was the whole story, tightening would crush the frame as it isn't much ticker than the fender in material.

Inside the frame at the attachment point are three heavy tubes that the bolts pass through. they space the side of the frame apart and when tightening they are squeezed. These tubes aren't loosely installed into the frame. They were originally built into a box that was inserted at manufacture and the whole thing spot welded together.

Once the frame has failed the first time all the internal box and tube structure is broken. For this ever to work securely again a good welder must cut a 3-4 inch diameter whole in the outside frame rail. Then he must reweld through the hole all the internal tubes. We also add some new bracing internally between the tubes. Then the hole must be rewelded and all cracks welded and reinforced.

We didn't come to this repair quickly. It took redoing a number of frames and a lot of exploratory surgury to come up with a repair that lasts.

[MikeTangas]

After checking the steering coupler as Steve suggests, there should be one last item to check - the sub-frame mounts (every other MB has them, the 123 should too). I had a very solid 'clunk' in the front end, turned out to be the sub-mounts. After replacement the clunk is gone, nice quiet ride. My mounts were still intact, but aged to the point they flexed so much the inner steel cone was making contact with the attachment bolt (clunk), and had worn partially through one bolt.