JBT3

Starting a dedicated thread to this noise I’m getting from the back of the car. Link to a video trying to capture the sound. It’s a lower frequency level whomp-whomp-whomp type noise (ignore the tiny rattles - that is just road debris kicking up under the car.

I thought this might be a wheel bearing, but I jacked up the car and can’t rattle or move the wheels at all. It’s not the wheels themselves b/c 2 different sets made the same noise. The noise is speed dependent but not consistent, meaning sometimes it’s not there and varies in loudness.

any ideas on how to diagnose or what this could be? Appreciate any input.

joejoe

Maybe half shaft need grease? (binding) It is a different sound, or brake/pad?

Tom. M

My rear bearings sounded like I was running super aggressive snow tires. I could make the sound go away by swerving left and then it would come back when swerving right. Replaced them and now nice and quiet.
Yours sounded more like something on a tire, or perhaps the road?

Mrmerlin

spin the front wheels off the ground,
look for binding or roughness in the bearing,
spin very slowly to feel this.
if nothing then,
its a safe bet one or both rear wheel bearings are going out.

NOTE check the axle nut torque first 320 FT/lbs 32 mm socket

Speedtoys

Ya know..for all the hassle its all worth....

If you dont know how old the bearings and axle shafts are....replace them all at once.

Noises like this roam all over the place, and 50/50 6mo from now you will have replaced most of it, to finally find it anyhow.

JBT3

Thanks for the replies guys. @Mrmerlin Stan - I’ll try the fronts. I have 3 torque wrenches but none go that high! Holy cow a torque wrench to hit that number must be really long. ( edit: I see some that go that high but might just take it to a shop if I can’t find one to rent somewhere.)

@Speedtoys I was afraid that might be the ultimate answer. I’ll dig through the cars records to see if I see mention of bearings or half shafts.

From what I’ve read this does not look like a very fun job.

Speedtoys

One at a time, its much worse...just diving in, not so bad.

Landseer

The axle nuts can be loosened with a 3/4 inch drive socket and handle, onto which you can slide a 4 or 5 or 6 foot pipe for leverage. I use a pipe made for holding the dies for bending 1 inch conduit, it was cheap and strong, though a tad short.

It's possible to tighten them well enough with such apparatus. You can then drive the car to a truck repair shop for torquing. Can access the nuts simply by removing wheel center caps. (I've done this job at least 8 times across various cars and just estimated the torque). The bigger worry is what to do with the outers.

Sounds to me like axles need to be replaced. My experience is that if they sound bad then they are worn. Often the ***** and raceways are pitted, making repacking questionable. Inner joints are replaceable with new. Outers can be repacked, but require a ton of effort to flush them clean first. Outers I think are a core that require a special rebuilder, they are not removable and can't be inspected. You can flush, repack, reboot and hope for best.

It's a little late to repack though once you hear the thumping. Repack is for when boots are broken, before the they start binding and making noise.

If found bad wear on inners, replaced them, and flushed/repacked the outers, flipped sides, and just called it good. Feels better to replace with rebuilt or new axles if you can find them.

Wheel bearings, that's a big enough extra job that I'd plan to replace the axles first to solve and go back in a second time if needed. You can feel the bearings with axles removed. Depends on your situation. Always more satisfying to do the WYAIT stuff, one fell swoop, replace all wear parts.

Another source of noise is torque tube bearings. My experience I'd they sound more gravelly.and less thump thump. Similar with rear wheel bearings, though more of a drone. Axles give off both a thump and drone.

Petza914

Bad wheel bearings usually make a rhythmic grumbling noise like a raw-raw-raw sound and as mentioned, if a front bearing the noise will be present when doing a long sweeping turn in one direction but not the other. It's also possible the front wheel bearings are loose and they're adjustable on our cars. If you remove the front wheel and the grease cap, you should be able to move the washer behind the bit with a little force and a screwdriver tip. If it slides with no resistance, the nut needs to be adjusted tighter.

joejoe

On my first sharktoberfest many years ago ('04 I believe) I had just rebuilt motor from tb failure on start up. Any way at the fest rear bearings were discussed and being paranoid took my car for a spin, and sure enough had the rear wheel symptoms. Made me not sure of the car I did not go on cruise but drove home instead. Pulled offending bearing (driver side was where 'noise' was from) and replaced, well after ruining 1 bearing, had it profesionally pressed in, put it together, and sure enough .....sound still there. As it turned out it was the tires with aggressive 'V' tread pattern sounding like bearing going out. The sound would dissappear when in turns (loaded) and come back when straight. Got rid of the 'V' tread tires (actually put them on the '90 944 cab.) and running more conventional tread pattern now with no wierd sounds. Kind of long to get to .... might be tire related...

Tom. M

Another question for you. Is the car driven regularly?
If not, sometimes the tires get flat spotted and it'll take some long driving to get them "round".
Check the pressures, and drive it some more to see if the sounds goes away or diminishes....
Check the easy stuff before you dive into replacing stuff...
good luck.

JBT3

had the same sound on two different sets of wheels and tires, so I’ve ruled that out.

driven weekly and I experienced flat spotted tires before. This is different.

I’m leaning towards a half shaft issue at this point. I want to check the inner bolts as a first step. I’ve been reading they often don’t get torqued down correctly. Wouldn’t be the first time on my GT where the fix was simple b/c the last guy to touch it was either lazy, incompetent, or both.

Speedtoys

"that's a big enough extra job that I'd plan to replace the axles first to solve and go back in a second time if needed."

You have to do all the same work to do these...I still vote that if these are 20yrs old, swap em, because you WILL be in there again...soon. If you have the tool, it's just a procedure...I mean, there's no way you can do them "by hand"..it's not that bad.

A growly set of axles has annoyed them...

19psi

Exactly what I hear on my car coming from the rear tires. Lighter the pavement the worse it gets and the hollow wop wop wop sounds are from tar snakes...fresher they are the louder it is, and in my area there can easily be over 1000 per mile. Find some freshly laid black top and the "bearing roar" and wop sounds disappear 100%.

JBT3

Well, inner bolts on the half shaft were tight. No noise when spinning the fronts off the ground. I don’t see anything loose on the rear suspension. I still need to fine a torque wrench big enough to check it’s at 320 ft/lbs but barring finding they aren’t torqued right, it Looks like the half shafts and bearings are getting R&R’ed.

doesn’t look too bad if I can get my hands on a Sir Tools B90 kit. Anyone got one to lend or rent? Happy to leave a deposit.

thanks
JT