Pulsing in Driveline - Need help diagnosing (1 Viewer)

[MaverickFiveO]

I'm the new owner of a 2009 GX 470. 105k miles on it. I'm thrilled with it, and makes trails seem easy that would have given me enormous amounts of heartburn in my old Outback. Everything is in pretty great shape, except I hear a pulsing in the driveline at any speed. I don't feel any vibration or pulsing until about 55 mph, then a small vibration through the wheel and seat (maybe 2mm of movement on the wheel at 75 mph). I don't know if those are related.

I can add that the sound is most noticeable when *rolling* down a hill. Under power, the sound is much quieter. It's loudest under engine drag, which is what makes me think it's somewhere in the driveline.

(Also, I just had new tires put on with a mount/balance/alignment, so I can rule that out. The brakes are also good, no warped rotors.)

Does this sounds familiar to anyone? I'll try to get a video with the sound uploaded soon.

I'm mostly concerned this is a symptom of a bigger problem, or that this is an imbalance that could cause problems if I don't address it soon.

Thanks!

 

[MaverickFiveO]

Describing this to a friend who is a mechanic, he suggested checking the pilot bearings. I'll dig into this more soon, but thank you in advance for any suggestions or help any of you can provide!

John

 

[GXO]

Sounds like u-joints to me. Could also be a CV outer giving up, or rear wheel bearings. Off chance the rear pinion is starting to kick it.

 

[ArBrnSnpr]

John,

I would throw some grease in the driveline and drive the same roads and see if there's any changes. If your noise is dulled, you likely need new u joints.

 

[MaverickFiveO]

I was afraid of the u-joints, but didn't want to bias it by mentioning them. I'll get under there and get it checked out. I'll report back with whatever I find and try to document my search. Maybe my efforts can help someone else down the road.

Thanks!

 

[joabmc]

You mentioned under engine drag... so along those lines, if you throw the vehicle in neutral while rolling down a hill does the vibration subside?
This may help you further isolate to the driveline or possibly a bearing.

 

[MaverickFiveO]

You mentioned under engine drag... so along those lines, if you throw the vehicle in neutral while rolling down a hill does the vibration subside?
This may help you further isolate to the driveline or possibly a bearing.

Good idea! I'll check that. I haven't tested it rolling in neutral. I live at the top of a canyon road, so I cruise down in 3rd or 4th gear, usually. Rolling down in neutral without braking for a while will be an adventure!

 

[MaverickFiveO]

Update: I tried the neutral rolling test. No change.

I tried cornering to test the CV and the wheel bearings. No change.

Greased up the u-joints. No change.

I gave up and took it to my friend’s shop. He drove it, and he couldn’t recognize it. We threw it up on a lift and hunted around.

The rear differential fluid is absolute glitter. Big shavings in there. The thing munched a gear tooth. The good news is that is a pretty definitive diagnosis. The bad news is that I need a new rear diff. This is probably the most subtle symptoms of a potentially serious problem I have seen on one of my cars.

I didn’t expect to be replacing something this significant this quickly on my new GX.

Thanks everyone for your help in trying to diagnose this. It helped me rule things out efficiently and ferret this out before something bad happened.

 

[GXO]

8" life. If you plan on wheeling it find an 8.2 cheap or go big for the axle upgrades.

 

[MaverickFiveO]

Dan, I would, except I got a pleasant surprise and the dealership is covering it. I have so little faith in dealerships, I had just written it off, but they are going to do the right thing and cover the rear diff. So now I have a stock differential, but it's a stock differential with a 12-month warranty on parts and labor...

...until I start playing in the rocks and dirt, at least.

 

[GXO]

Very nice!!