Say Goodbye to the Flat Spotted Tires / Shuttering Theory

[arcman]

Finally got around to getting the car up in the air to do some investigating. With three items on the list, this turned into a two-dayer. Rotate tires, craft a drain line so I don't have to lift the car to change oil (yeah, I did just buy a vacuum pump but it will be quicker this way). The third was the driveline shutter/noise.

I actually got quite elaborate/anal on this (I tend to do this on a lot of things). I set up three lav mics and laptops running Audicity to record where the noise was coming from. One mic on the rear u-joint on the front prop shaft, one on the rubber coupler and one on the mid bearing/U-joint.


With the car up on stands under the suspension so the axles weren't in droop, I ran the car up to 30mph. Expecting to hear the usual clicking, it didn't happen. But... it had a nasty vibration like I've never felt before. My car just emits a few minutes of clicking from under the console and then it goes away. One key thing with this test is the wheels were off. So that ruled them out.

Since the clicking I expected didn't happen, the mics didn't help much. Big waste of time in setting all that crap up.

Here's the reason you can kiss off the tire theory... I disconnected the rear driveshaft rubber coupler from the trans, ran it up again to 30mph and the vibration is GONE. (I assume the clicking also) Too bad you can't road test it this way without completely removing the rear driveshaft.



Before I bolt it all back up, I wanted to check with others here who have the vibration. I've never really noticed the vibration, maybe because the 30mph portion of roads from my house to town or to the interstate are so rough, I never feel it. After five miles there's no clicking. This only happens on the initial drive of the day.

Does your vibration lessen after a few miles? If that is the case, I'm leaning again to the rubber coupler. If it were a rear driveshaft balance issue, it would be there every time the car was at 30mph.


Here's a couple pics of the drain hose. I found a 14mm x 1.5 to AN6 adapter for the pan. A hose which leads to the outside of the car behind the front left fender well liner. I put an old ratty piece of firesleeve over the hose where it is near the exhaust to protect it from heat. I ty-rapped it near the outer edge of the undertray panel and when it comes time to drain the oil, I'll just snip the ty-rap and let it hang out over a pan.

 

[Markymark]

Nice work!

Yes, my fluttering goes away after a few miles. Worse when it’s cold out. Not really noticeable at all during the Memphis summers.

 

[Gennadiy]

So how much to replace that coupler to see if it fixes it? Looks like the rest of the rear end was disconnected during the trial as well so I guess the vibration could be coming from anywhere past the driveshaft. Anyone know if it’s one of the things replaced when they swap the driveshaft for the flutter noise fix? I had my driveshaft replaced but the vibration is horrible.

 

[princelybug]

Nice work!

Will some of the oil remain in the drain hose when changing the oil?

 

[arcman]

princelybug...

Glad you asked that. I took another look at the hose routing and when going over the cross member, it actually gained 3/4" over the oil pan outlet so I routed it under. Didn't need the firesleeve after that.

To answer your question, it's slightly downhill from the pan to the end of the hose. All of the oil should drain out. And if any did stay in the hose it's negligible.

 

[arcman]

(I posted this on one of the other 'Flutter' threads.)

I am now 99% convinced the problem is with the flexible coupler on the back of the trans. Yesterday I swapped that coupler for another used one and the vibration was cut in half. I believe the coupler takes a set when parked overnight (worse the colder it is) and it takes a few miles to 'loosen' it up and then the problem goes away. I also believe this is why replacing the dirveshaft may fix it for a while but it eventually comes back.

I am starting to think (uh, oh... conspiracy theory...) this is one of those 'dirty little secrets' the automotive industry doesn't want to talk about. How on earth could something so common on these cars not be dealt with by Hyundai? They've replaced owners driveshafts, tires, transmissions, transfer cases and rear ends and (eventually) none of these fixes seem permanent. One other thing to contribute is the rubber center bearing support. The used driveshaft I purchased, the center support has sagged considerably, creating more of an angle between the shaft and output flange on the trans. This bends the coupler even more so the flexing during a rotation is amplified.

I've got calls out to manufacturers SGF (who makes our coupler) and Dana Spicer but no one's in a hurry to get back. I'm guessing they won't.

 

[Kraig Wilkinson]

Finally got around to getting the car up in the air to do some investigating. With three items on the list, this turned into a two-dayer. Rotate tires, craft a drain line so I don't have to lift the car to change oil (yeah, I did just buy a vacuum pump but it will be quicker this way). The third was the driveline shutter/noise.

I actually got quite elaborate/anal on this (I tend to do this on a lot of things). I set up three lav mics and laptops running Audicity to record where the noise was coming from. One mic on the rear u-joint on the front prop shaft, one on the rubber coupler and one on the mid bearing/U-joint.

View attachment 29513
With the car up on stands under the suspension so the axles weren't in droop, I ran the car up to 30mph. Expecting to hear the usual clicking, it didn't happen. But... it had a nasty vibration like I've never felt before. My car just emits a few minutes of clicking from under the console and then it goes away. One key thing with this test is the wheels were off. So that ruled them out.

Since the clicking I expected didn't happen, the mics didn't help much. Big waste of time in setting all that crap up.

Here's the reason you can kiss off the tire theory... I disconnected the rear driveshaft rubber coupler from the trans, ran it up again to 30mph and the vibration is GONE. (I assume the clicking also) Too bad you can't road test it this way without completely removing the rear driveshaft.

View attachment 29514

Before I bolt it all back up, I wanted to check with others here who have the vibration. I've never really noticed the vibration, maybe because the 30mph portion of roads from my house to town or to the interstate are so rough, I never feel it. After five miles there's no clicking. This only happens on the initial drive of the day.

Does your vibration lessen after a few miles? If that is the case, I'm leaning again to the rubber coupler. If it were a rear driveshaft balance issue, it would be there every time the car was at 30mph.


Here's a couple pics of the drain hose. I found a 14mm x 1.5 to AN6 adapter for the pan. A hose which leads to the outside of the car behind the front left fender well liner. I put an old ratty piece of firesleeve over the hose where it is near the exhaust to protect it from heat. I ty-rapped it near the outer edge of the undertray panel and when it comes time to drain the oil, I'll just snip the ty-rap and let it hang out over a pan.

View attachment 29518

View attachment 29516

View attachment 29517

Nice work arcman! You are an artist.

 

[ntmehan]

(I posted this on one of the other 'Flutter' threads.)

I am now 99% convinced the problem is with the flexible coupler on the back of the trans. Yesterday I swapped that coupler for another used one and the vibration was cut in half. I believe the coupler takes a set when parked overnight (worse the colder it is) and it takes a few miles to 'loosen' it up and then the problem goes away. I also believe this is why replacing the dirveshaft may fix it for a while but it eventually comes back.

I am starting to think (uh, oh... conspiracy theory...) this is one of those 'dirty little secrets' the automotive industry doesn't want to talk about. How on earth could something so common on these cars not be dealt with by Hyundai? They've replaced owners driveshafts, tires, transmissions, transfer cases and rear ends and (eventually) none of these fixes seem permanent. One other thing to contribute is the rubber center bearing support. The used driveshaft I purchased, the center support has sagged considerably, creating more of an angle between the shaft and output flange on the trans. This bends the coupler even more so the flexing during a rotation is amplified.

I've got calls out to manufacturers SGF (who makes our coupler) and Dana Spicer but no one's in a hurry to get back. I'm guessing they won't.

Would be curious to see what others who have this issue's parking habits are. If it's the flex-coupler, then is it better if you set the parking brake prior to shifting into P and the pawl applying to the trans, thus unloading the drivetrain and coupler? I park in my garage facing out and just put the trans in P (no parking brake) so the car pulls against the parking pawl in the forward direction. I'm still having the flutter on my first drive of the day even though temps have heated up here and the garage is staying in the upper 60s (I'd guess) at the lowest. How does everyone else park?

 

[Gennadiy]

I inside a level garage. It’s well over 100 degrees in the garage when I leave for work in the afternoon and the vibration is there.

 

[TinsleyC]

Wonder what would happen if you put the car in reverse before setting the parking brake, then go to park and power down. Might stress the flex coupler the other way?

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[Gennadiy]

Wonder what would happen if you put the car in reverse before setting the parking brake, then go to park and power down. Might stress the flex coupler the other way?

I’ll do you one better. I’ll apply the ebrake and leave it in neutral overnight. I’ll let you know what happens.

 

[Suburbazine]

I’ll do you one better. I’ll apply the ebrake and leave it in neutral overnight. I’ll let you know what happens.

battery will go dead if not on a 20A charger.

 

[Gennadiy]

battery will go dead if not on a 20A charger.

I’m not going to leave the car on. Not sure why the battery would be draining.

 

[Kraig Wilkinson]

I’m not going to leave the car on. Not sure why the battery would be draining.

It will keep making a dinging noise saying that you are not in neutral.

 

[Gennadiy]

It will keep making a dinging noise saying that you are not in neutral.

Well isn’t that something. It sure did. I used the manual release button to put it in neutral after shutting it down in park.

 

[ntmehan]

Could just turn off the main switch in the interior fuse box, right?

 

[arcman]

Most likely that won't help. But, if you bump the car from it's position enough to rotate the driveshaft 180 degrees an hour before you drive the car for the first time of the day, it may make a difference.

My thinking here is the coupler takes a set when left in position overnight (more so in colder conditions).

The shot below is over exaggerated but this is what's happening on each revolution of the driveshaft. Each of the three mounts on both the trans flange and the driveshaft flange are pulling and pushing (forward and backwards) on the coupler because of the angle offset.



A couple days ago I had a nice long talk with an engineer who works for a firm in the Detroit area that specializes in automotive rubber isolation and vibration. He said this a quite common. They've worked with Chrysler and Ford and one big problem in particular was with the Ford Mustang. They had thousands of complaints about vibration and noise in the driveline. It all came down to harmonics. Just like the Genesis, it only vibrated at certain rpm's. On most cars it didn't show up until around 30K miles but some had the problem with only 5K on them.

He did agree with my 'dirty little secret' comment and that car manufacturer's focus on comfort and quiet for this type of car. That's why they went to the rubber coupler in the first place. Make it dazzle to make the sale. After that they don't care. He even said they designed a suspension part that would last forever and Chrysler said "why would we want that?" Their reply was they wanted it to last five years max. There's a huge incentive to sell parts. Our driveshaft is one good example. You can't buy the coupler from Hyundai and the U-joints are not replaceable. Much better to sell a $1,100 driveshaft then a $40 U-joint. That's a trend with many car makers.

I am a bit disappointed in seeing that Genaddly still has the issue in 100 degree heat. I was thinking heat would help. Only thing left to try is rotating the shaft before driving.

Still no word back from SGF or Dana/Spicer and I want to find why the current part was superseded before buying one.

 

[TinsleyC]

Excellent info, arcman!

 

[osnv]

Most likely that won't help. But, if you bump the car from it's position enough to rotate the driveshaft 180 degrees an hour before you drive the car for the first time of the day, it may make a difference.

My thinking here is the coupler takes a set when left in position overnight (more so in colder conditions).

The shot below is over exaggerated but this is what's happening on each revolution of the driveshaft. Each of the three mounts on both the trans flange and the driveshaft flange are pulling and pushing (forward and backwards) on the coupler because of the angle offset.

View attachment 29768

A couple days ago I had a nice long talk with an engineer who works for a firm in the Detroit area that specializes in automotive rubber isolation and vibration. He said this a quite common. They've worked with Chrysler and Ford and one big problem in particular was with the Ford Mustang. They had thousands of complaints about vibration and noise in the driveline. It all came down to harmonics. Just like the Genesis, it only vibrated at certain rpm's. On most cars it didn't show up until around 30K miles but some had the problem with only 5K on them.

He did agree with my 'dirty little secret' comment and that car manufacturer's focus on comfort and quiet for this type of car. That's why they went to the rubber coupler in the first place. Make it dazzle to make the sale. After that they don't care. He even said they designed a suspension part that would last forever and Chrysler said "why would we want that?" Their reply was they wanted it to last five years max. There's a huge incentive to sell parts. Our driveshaft is one good example. You can't buy the coupler from Hyundai and the U-joints are not replaceable. Much better to sell a $1,100 driveshaft then a $40 U-joint. That's a trend with many car makers.

I am a bit disappointed in seeing that Genaddly still has the issue in 100 degree heat. I was thinking heat would help. Only thing left to try is rotating the shaft before driving.

Still no word back from SGF or Dana/Spicer and I want to find why the current part was superseded before buying one.

Excellent info, arcman. However, from what you described, it appears that even if the brand new coupler is installed, it will be subjected to the same "abuse" by the driveshaft, the vibration will quickly return, and the coupler replacement will not completely/permanently fix the vibration issue. Or am I missing something?

 

[arcman]

That is correct. That's why some owners report the problem coming back after Hyundai replaces the driveshaft.

Maybe I'm talking out my butt here but that is why, after (and before) speaking to that engineer, I feel it's a problem that won't get fixed and Hyundai is just appeasing owners by replacing parts. The small crowd getting parts tossed at their cars is way cheaper than Hyundai admitting there's a problem, engineering a fix, tooling up and possibly having to recall tens of thousands of cars. Why else would Hyundai replace all these expensive parts when we know for sure it's coming from the rear driveshaft? I proved that by removing three bolts, and I am not the first to figure this out.