In my '84 300tdt, I have knocking sound when going over bumps from front left of the car...sounds exactly like a bad lower ball joint...especially pronounced when driving over "washboard" surface...dirt roads, rail road tracks, etc....

BUT when I try to confirm this by jacking up front end, I cant confirm a bad ball joint, or find anything with obvious play....I have done the following:

- jacked up front left, shake wheel with hands, lift wheel quickly with a lever...no knocking sounds...ball joints seem ok...wheel bearing/spindle nut tight, no play.

- tightned lug nuts in case of loose wheel...they were fine

- removed upper control arm (UCA)...which was replaced recently, and checked ball joint, rubber torsion bar bummpers, etc... upper control arm is like new, ball joint very tight with no play

- while the UCA was removed, I held the steering knuckle/rotor/caliper assembly in my hands and rotated it around on the lower ball joint, and violently shook up and down, side to side, etc., and I feel absolutely no play in the ball joint.

- grabbed onto other suspension components and shook....no play

- I checked for any other odd item that might be knocking (exhaust system, front grille components) and checked if maybe I left a tool in the engine compartment, and everything seems tight

- I recently installed new bilstien shocks...I checked to make sure that all bolts/nuts were tight, and the both rubber "bumpers" were in place...everything ok

-checked torsion bar bushing under brake booster...its fine (the knocking sound is not in that vicinity, its lower toward the front)

When I put everything back together, I'll be darned.....the knocking sound is still there!!! I would swear it is the ball joint, but I can't verify!

The car has new tie rods, new guide rod bushings and mounts.

I haven't removed the new bilstien shock to see if it is bad...I cant imagine this to be the cause.

What am I missing?

Thanks,

Mark

__________________
1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)

A ball joint is a very stiff device.............even when it's bad..............it takes many hundreds of pounds to move it. You'll not move it by shaking the wheel or attempting to move the wheel with a lever.

You've got to get a big prybar between the LCA and the spindle and attempt to force the ball joint off the LCA. At that moment, you can see the movement in the ball joint. How much to allow is generally a matter of opinion, but, if the joint is truly bad, you'll see a decent amount of movement...........1/4" inch or more.

NYS inspection used to include ball joints. My recollection is that a mechanic would typically jack the tire off the ground and put a large pry bar under the tire and pry up while the joint was observed.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

That's how I've always seen them checked too.