Front end messed up after steering knuckle swap w123 -> w126
 

Swapped out steering knuckles from my '85 w123, non-abs, for a set from a 1985 w126 with ABS today, and also replaced my front rotors. Now that it's bolted back together it's driving awful. Steering feels very odd, like a sloppy steering box (very light and no desire to self-center), and when the wheel is turned to go around a corner it wants to pull hard to that side.

Background: Point of this was originally to buy the second set of knuckles to have new lower balljoints pressed in and ready to go, to avoid taking the car off the road during the balljoint change. However, when my friend parted out the w126 that was to serve as the knuckle donor, he discovered the balljoints looked nearly new so I decided to just stick with them and install the knuckle as-is.

I did move the w123 backing plates over to the w126 spindle, as the ABS ones are quite different.

It has been a long day in the sun and I may be buzzed enough to have missed something. I am going to start pulling it apart again tomorrow but if someone has input based on the symptoms, it will be most appreciated.

These knuckles are supposed to be a direct swap item, however right now if I had to guess, I would say that the car feels like it has tierods that are mightily out of whack (feels a bit like a car I bought once that had hit a curb hard and bent the tierod and center link).

They are a direct bolt on, but I don't think there is consistency in the casting process. So my hunch a wheel alignment would fix the issue.


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Thanks for the reply, and glad to hear that comment. I had it fixed in my mind, for whatever reason, that an alignment wouldn't be needed, so it wasn't even on my radar.

I don't like posting on Saturday evenings as it seems like a pretty dead zone....

I swapped a spindle from an ABS W126 into my non-ABS 300SD because I had a ball joint pressed into the new spindle. I don't notice any difference but then again, I went from W126 to the same. You should not have to do an alignment for a ball joint replacement unless the old ball joints were extremely worn.

Now that I have driven it after a night's sleep and in a more calm state of mind, I can readily see this is an alignment issue.

Also whomever installed the previous balljoints didn't tighten them down properly. It would appear they stopped turning the locknuts as soon as they started to get snug. It took very little to remove the nuts yesterday.

I am thinking that as the car was aligned previously that way, after I changed the center link and one tierod when I got it ~19k ago, the reinstall itself was enough to throw off the alignment.

I also hear the comment on the knuckle possibly being slightly different, in fact my friend who provided them raised this question just from his visual inspection. I did put them side by side at one point but I wasn't too concerned about a minute inspection.

When I was bolting up the right tierod the fit just seemed a bit odd, like the opening in the knuckle was oversized versus the original one. I didn't think overmuch about it at the time.