kingpin play? - PeachParts Mercedes-Benz Forum

n10 · #1 01-23-2015, 12:58 AM

Hi folks,

So I have been getting a good vibration through the steering wheel/car from 50-65ish. I am looking at all the suggestions from searching but I think I may have an idea of what it might be...at least part of it.

How much play in mm is acceptable in the kingpins? The driver side barely moves but the passenger side has almost 3-4 mm of jiggle

Thanks

Tony H · #2 01-27-2015, 12:15 AM

There should be no perceivable movement. Usually the link pins are what wear out not the actual king pins.

n10 · #3 01-28-2015, 04:51 PM

Well turns out that wasn't the only thing causing the vibration.

Found my flexdisc cracked in half and one of the bolts just hanging there. The nut to it disappeared somewhere on the road! The drive shaft didn't separate completely, (thank the goodness) but did break at one of the flexdisc mounting points. Replacement driveshaft enroute and will be back on the road by Friday.

I guess I got lucky as no other damage happened

Idle · #4 01-28-2015, 10:22 PM

A carrier bearing normally makes a bit of a rumble during starting and stopping but smooths out the speeds you are talking about.

But this is not the carrier bearing.

Can you describe the sounds and feelings for future reference? I would love to know just what you were hearing and feeling so when and if it happens to me I would know what was going on.

n10 · #5 01-29-2015, 02:29 PM

Sure! Keep in mind that I have an auto trans.
Well it started as a slight vibration at 60 for about a week but would go away around 70. During hard accel up hill it was more pronounced. Could feel it in your butt and steering wheel and see the rearview mirror shake.
Fast forward a week.. it would still happen up hills and at 60+. Once everything got warmed up, (20 min of driving) it would happen for a moment around 40 then smooth out till 60. At coasting the vibration picked up more at those speeds.

Toward the end after I found the bolt hanging out and really saw the damage... I limped it to my mechanic buddy about 2 miles from home. That was a terrifying short drive. Accel was sketchy but coasting was sloppy as all get out. Thankfully it was rush hour so I never got above 30 which at that point was very sloppy. Coming to a stop when the auto would downshift it would hit pretty hard and you could tell there was slippage.

I should have had it towed but I didn't want to cash in one of my free tows for 2 miles. It got there fine without further damage but next time I won't take the risk.

Hope that helps!

Tony H · #6 01-29-2015, 09:14 PM

Another good reason to check rubber parts regularly. You don't want to know what happens when the flex disc fails. Glad you found it time.

n10 · #7 01-29-2015, 11:01 PM

Those stories were all I could think about on my short drive that day

Tony H · #8 01-30-2015, 10:48 PM

I have heard of the driveshaft coming through the floor when a u joint or flex disc fails

Baxterdown · #9 01-31-2015, 09:47 AM

n10

Make sure your mechanic marks the driveshaft and puts it back in the way it went out or you'll end up having to rebalance it. -- I learned that tip from the experts here

I wanna hear if your vibration goes away after replacing the flex disks.

I've had an ongoing vibration since I got my car last year. I started with replacing the flex disks, then onto king pigs, and engine mounts, and trailing arm bushings, and tires, etc. It's still there.

The only thing I haven't done is re-balancing the driveshaft because the vibration is not present at all times. It's only there between 30-40 miles per hour and much more prevalent when its cold; less pronounced when its warm. I was told by my mechanic that if it were the driveshaft the vibration would be there all the time.

Keep us posted on your progress!

Jose

Carpenterman · #10 01-31-2015, 10:09 AM

I'm not sure your mechanic is correct about vibration all the time with an unbalanced driveshaft. My experience has been that an unbalanced driveshaft assembly has a resonance that may cause vibration only at certain speed.

Tomguy · #11 01-31-2015, 11:08 AM

I agree with Carpenterman. Harmonics in a driveline can be a funny thing. Too slow, the driveshaft can't overcome the play in the flex disc, u-joint, carrier, etc; no vibration. Too fast, and it can't vibrate because it's being bound up by extra forces in those areas that reduce or eliminate the play at speed (Centripital force, torque, and other fun physics things). The Goldilocks speed of "Just right" and you get the vibration. The driveshaft should be balanced independently of the rest of the drive system, I am not 100% sure if this is how MB did it "Back in the day" at the factory, but replacing a flex disc (hopefully not with a Uro one) would potentially unbalance said factory balancing. 1 gram here, 1 there, on a driveshaft that spins fairly rapidly, and you can get a shimmy at what otherwise seems like random speeds and even then sometimes only on some conditions (coasting, deceleration, acceleration, cornering while flogging it, cornering like a granny carrying 12 dozen eggs in her trunk...)

Baxterdown · #12 02-01-2015, 09:30 AM

Tomguy, LOL!!! That's funny!! -- Thanks for the great info guys.