grind? grumble? roar?

Hey guys,

Well, I am out in Reno now, and my VX made it. However, I am wondering about a new noise I am hearing now. I started noticing it as I was going up and descending steep mountain roads. There is a lot of this out here, and its going to be common place for me from now on.

Anyway, the sound is what I belive to be my diffs or trans grinding or stressing. I only hear it when I am accellerating and in gear. After I come down a steep hill, and stop at a light, I can hear and feel the VX growling. If I put it in NEUTRAL or PARK, the growling stops. Whatever the sound is, it does not sound good or normal. I did have my diff fluids changed right before I left. Also, it is shifting totally smooth and normal and driving seems otherwise unaffected. And this is why I am leaning toward my diffs.

Anyone have any ideas? I read a few older threads about diff noise and driveline noise, but the symptoms seem to be different (i.e., when coasting, I do not hear or feel this grumbling sound). I have not been able to determine if the noise is coming from the front, rear or middle of the VX. Its hard to tell over the sound of my roof rack slicing the air and the loose jar of change underneath that rattles non-stop (I gotta find this loose thing, its driving me nuts, I already found one loose heat sheild but it was not the culprit).

Any help would be appreciated...

Thanks -Bart

If the noise is only under load (like uphill, cruise or acceleration) then typically that's differential related as the power transmission is at 90 degrees. If it just started after changing your diff lube then you may want to try a different grade or type of lube. Fortunately this is something you can experiment with since changing diff lube is simple, quick and inexpensive.

Usually diff noise is more of a whir/whine than a groan or roar. I did have a friend call once about something similar when she was on the road and it turned out to be the local road surface, which was significantly coarser than anything she had noticed driving on previously.

Yeah, I personally think it must be the diffs, probably the front diffs. Like I said, the tranny is shifting nicely so I do not think this is the issue. Tomorrow I'm gonna zoom around with POWER MODE turned on so I will see what happens with that. The roads out here do make more noise, and the wear on my brakes and tires is probably going to double compared to flat Illinois. That said it is not road noise, as I can hear this grumble when in gear and stopped at a red light.

My mech did tell me that I will probably hear some noise from the diffs after a fluid change, don't know the logic behind that however.

I did do a hell of alot of cruising on my way out here too. After the 8th hour your legs start to cramp up and the cruise becomes a very nice feature. I did not cruise when going uphill however as I noticed the cruise control tries to compensate for the incline and I do not care for the stress it puts on the engine and tranny when it handles it with the cruise control.

Someone needs to do a tutorial on changing the diff fluids (with photos) hint, hint.

:) Bart

PS - Also, a "A guide to finding wierd under-carriage rattles for VX owners" needs to be written up as well. ;)

Quote:

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Originally Posted by Joe_Black

If the noise is only under load (like uphill, cruise or acceleration) then typically that's differential related as the power transmission is at 90 degrees. If it just started after changing your diff lube then you may want to try a different grade or type of lube. Fortunately this is something you can experiment with since changing diff lube is simple, quick and inexpensive.

Usually diff noise is more of a whir/whine than a groan or roar. I did have a friend call once about something similar when she was on the road and it turned out to be the local road surface, which was significantly coarser than anything she had noticed driving on previously.

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If it makes the noise while you're sitting still then that's not the diffs. That little tid-bit of info would indicate something engine or accessory (Fan, AC compressor, alternator, PS pump etc.) related as those are the only things in operation while your stationary and running. In that case you need to pop the hood while the engine is running and just alternate from one fender to the other while you gaze into the wonders of the engine bay. ;) Hopefully your ears will point your eyes to the culprit.

If you look in my gallery I've got some pics of the drain and fill points for the diffs. Locating the fill and drain is the hardest part of doing the diffs.

As for your cruise control, there really isn't any additional strain put on the engine. The cruise control actuator is simply a servo that moves the throttle based on your speed preset and info from the speed sensor. Since it doesn't move the throttle as aggressively as your foot it can take some time to reach the kick-down point for the tranny to go into a lower gear for inclines, and that can get annoying in hilly areas.

Keep us informed on the noise issue, I'm curious with it happening while stopped. :confused:

Hey Joe,

Well, I have determined that the noise seems to be a vibration. When I come to a stop after a good drive, I can hear and feel the vibration from what seems to be the front end.

Now, yesterday, I was sitting in a parking spot with the vibration happening and I cut the front wheels all the way to the left, and the vibration stopped. I turned the wheels back straight again and the vibration returned. Again, this is with my foot on the brake and in DRIVE. If I put the VX in NEUTRAL or PARK the vibration stops completely, no matter which way the wheels are pointing.

Once I get into a house (hopefully this week) I will be able to get under there and see a little more hopefully. I need to figure this out.

Bart

Quote:

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Originally Posted by Joe_Black

If it makes the noise while you're sitting still then that's not the diffs. That little tid-bit of info would indicate something engine or accessory (Fan, AC compressor, alternator, PS pump etc.) related as those are the only things in operation while your stationary and running. In that case you need to pop the hood while the engine is running and just alternate from one fender to the other while you gaze into the wonders of the engine bay. ;) Hopefully your ears will point your eyes to the culprit.

If you look in my gallery I've got some pics of the drain and fill points for the diffs. Locating the fill and drain is the hardest part of doing the diffs.

As for your cruise control, there really isn't any additional strain put on the engine. The cruise control actuator is simply a servo that moves the throttle based on your speed preset and info from the speed sensor. Since it doesn't move the throttle as aggressively as your foot it can take some time to reach the kick-down point for the tranny to go into a lower gear for inclines, and that can get annoying in hilly areas.

Keep us informed on the noise issue, I'm curious with it happening while stopped. :confused:

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Thanks for the additional info Bart. The turning of the wheels puts a load on the PS pump, and that it happens only while the driveline is torqued up helps. I'm going to share this info with some mechanic friends and see what comes up as I'm drawing an ineffective blank just yet. :p

Hope to have something for you very soon if no one else forwards a theory in the interim.

OK cool, I did have my PS fluid changed before I left, but my steering seems totally fine...

Thanks - Bart

Quote:

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Originally Posted by Joe_Black

Thanks for the additional info Bart. The turning of the wheels puts a load on the PS pump, and that it happens only while the driveline is torqued up helps. I'm going to share this info with some mechanic friends and see what comes up as I'm drawing an ineffective blank just yet. :p

Hope to have something for you very soon if no one else forwards a theory in the interim.

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Bringing this post back to life. Has the cause of this problem ever been identified? I'm having the same symptoms.

where it sounds like a roar while you're driving/accelerating? yeah, i'm having that too. I think it's a GM thing...since my wife's Sonoma has the same issue.

I am also having the same issue, anyone ever solve this?