Re: 2006 Sonata Rear Suspension Noise--SOLVED.

Happy to HT.

Looks like you may get the part no. before me.

They sent me home without a fix, but said the parts were being shipped from Korea. The part numbers haven't even been assigned yet. My Service Manager was puzzled that the fellow I mentioned had a fix already. He said it must have been an experimental fix, because no official parts exist yet according to Hyundai.

Highest praise go to my SM and Tech. They were very patient and nice, and very sincere in wanting to resolve the problem. As soon as the parts come in, they will set me up with a loaner and apply the fix. Why a loaner for a 30-45 minute fix? My guess is that he wants to have a show and tell on the procedure with the Techs, and drive the car a good bit before and after the fix.

Incidentally, the Hyundai Rep. said the problem is specific to the V6. The I4 has different shocks, as you are aware.

Maybe Hyundai buys the I4 shocks from a different supplier, and that's why the bushing material (or size) is defective only in the V6 shocks. All speculation on my part! -

Bob

Right now you're on pretty much the ground floor of an engineering solution. Someone figures out (or thinks the've figured out) the cause of a problem and they create a potential repair. Technical assistance usually gets a small supply of parts for these repairs and sends them out to a few cases and monitors the results. If it works well, a TSB is typically issued (after a significant period of time) with repair and part information. If this solution is still in the experimental stage, it's somewhat likely that there is not yet a part number, and Hyundai will just send the parts free of charge to the dealer.

I'd wager that the cause of the issue being present on the V6 and not the four cylinder is one of the following:

1. The difference in the stiffness of the suspensions makes a difference in resonance, and/or
2. The four cylinder engine is just loud enough to make the noise less noticeable.

I think "defective" is probably a strong word. More likely, there's nothing wrong with the bushing that prevents it from operating properly, but it's constructed in such a way that it transmits the thumping noise a little too well for the driver's aural comfort.

Funny, nobody told my I4 as it makes a noise in the rear suspension from time to time. Or is your noise in the front? I'm wondering why the rear shocks would differ from the I4 to the V6? That doesn't make much sense as the weight difference at the rear from the 200 lbs or so of weight different up front would be negligible.

Matt

That's exactly what I've been doing for the last 40 years. Requesting engineering changes, testing the changes, final approval, the whole process is very familiar to me.

You're right. It could be something as simple as the Durometer in the rubber or urethane compound. Too soft and it allows too much movement, too hard and it could transmit noise to the body. It may not even be the bushing for all I know. It could be a slight mismatch in the shock profile and the spring rate... which is about what you said.

It could be noise transmission through the shock mount due to lack of rigidity, aggravated by sudden fast movement of the shock. Don't know if the shock mounting pads are welded on or bolted on. If bolted on, a rubber pad under it could help isolate the drumming noise.

Regardless, I'm impressed with my SM and the Hyundai Rep. for coming up front. -

Bob

I spoke to a Hyundai field engineer today and asked him about this. He indicated that there were new struts with a different damping coefficient and new, softer bushings. I got the impression this was phased in for the '07 model year.

It's possible the retrofit may be for the bushings only to avoid introducing ride quality complications from changing the damping coefficient.

Is this the specification for the production build now (Korean build for the UK)? Any way of finding out when this was introduced? cheers nn

Thanks for the info HT!

I just got a P/N from the original person (mat22trees) that got the first fix:

P/N: 3536966 Description: Seal, 1.456"

That doesn't sound like a bushing or pad as Matt first reported. I'll chalk that up to normal miscommunication.

Bad news: Matt reports that while the fix improved the K-thunk noise, it didn't eliminate it.

Good news: He reported that the noise was reduced enough to satisfy him.

If it improves around 50%, I'll be satisfied too. I will report back as soon as I hear something from my dealer. -

Bob

Unfortunately, 3536966 isn't a Hyundai part number. I suspect that the dealer, like I alluded above, received the parts for free and this was simply their way of recording them on the repair order with a number assigned by them.

Hyundai part numbers will have five digits, a dash, and five more digits, typically. The first five indicate the type of part and the second five indicate model (loosely) and revisions.