Need help diagnosing bad vibration

[jaggedfish]

Hey all,

My van has recently acquired a bad vibration/banging thing when driving. Basically, when I am driving I get a regular clunking sound but when I ease off the throttle the clunking and vibration gets worse - even at speed - and the van sort of jerks along as if it has a warped brake disc. When slowing to a stop, the jerking is like something grabs then lets go at regular intervals.

The vibration (for lack of a better description) is at regular intervals which would indicate to me that it is cause by something that rotates. It slows as the van slows and speeds up as the van speeds up. I don't feel it in the steering wheel which makes me think it is either in the driveline or rear brakes. I haven't had any hot brake smell. Front calipers were recently replaced at CVI. A quick check of the temperature of the hubs after driving indicated the driver side rear was a little warmer than the other three sooo... maybe a brake problem?

The only reason for doubting the brake problem is the vibration gets quite severe when feathering the throttle (letting off the throttle but not all the way) while driving.

Has anyone had any similar experiences. Any suggestions? I am on the Sunshine Coast so it's not as simple as taking it to CVI for diagnosis...
Thanks for any input... will check back later today.
Cheers!
Ian

[Big-Bird]

Check the universal joints on the rear drive shaft. From what you listed it is most likely a U-joint with excessive play.

[nxski]

I have basically the same symptoms, I replaced the u-joints which helped but didn't get rid of the problem, the wheel being out of alignment causes more vibration as well, but unfortunately I've yet to find the root of the problem.

[RickJ]

Same issue with my l400

[jaggedfish]

Thanks for the replies!

I think I may have found the problem... seems like it might be the passenger rear brake has seized or partly seized. The wheel hub was definitely warmer than the other three after a drive and a bit of a burning brake smell as well. Will have to have a closer look. The vibration only shows up after driving for a short while - presumeably once the brake heats up - and occasionally goes away after a while so perhaps the brake is not entirely seized but well on it's way and in need of replacement.

It is a tough one to diagnose based on vibration alone as it lessens when the drivetrain is under load and gets worse when there is no load but still rolling. Will see if this is the culprit...

Cheers!
Ian

[RickJ]

I had the exact same issue. I replaced both the rear calipers but the problem still persists. I keep a temp gun in my tool box and every now and then when it becomes bad I hop out and check the temps of all 4 hubs and rotors. They have maintained even 20's all around so I'm not convinced this is my problem. Keep us updated please.

[jaggedfish]

RickJ... when you did your rear brakes did you have the rotors turned or replaced? The heat from a seized caliper is enough to warp the brake rotor so they must be turned or replaced so they spin true again. Just replacing the calipers will only fix part of the problem and you will likely still feel the surging or bumping because the pads are only hitting the rotor in the "high" spots. In that situation you shouldn't notice any significant heat problems because the brakes are still able to cool off but the brakes won't do their job fully as they can't fully grap the rotor. Just a thought on that.

Will be looking into mine as soon as I can and will report back.
Cheers!
Ian

[jaggedfish]

Okay... so I finally have a bit of time to report back on the problem I had...

Replaced the rear rotors, calipers and pads last Monday and the problem is now gone! The driver's side was seized hard and I had to hammer the caliper off the rotor just to remove it! The job is very easy to do at home - only 2 bolts and a brake line on each side.

Now I am back in business building our new hot tub deck!
Cheers!
Ian