Saturn Sky Forum banner

1 - 6 of 6 Posts

·
Premium Member
Joined
·
552 Posts
Discussion Starter #1
So I have noticed lately that whenever I first start out on a drive there is very distinct rotational humm/vibration that can be heard inside (top up)and felt in the gas pedal. It only occurs during on-throttle and not when coasting; in or out of gear. It comes and goes rhythmically/ cyclically (what I call rotational) as I accelerate. It does get somewhat faster as I increase speed but not in relation to the amount of RPMs from the engine (the engine revs faster than the humm/vibration increases). It does tend to go away the longer I drive it. When I first start off it does get pretty noticeable in the "feel" of my hands on the steering wheel. It only occurs when "on-throttle", so I'm not thinking of anything to do with wheel bearings, brake pads (I only say that because I just recently replaced pads/rotors) or tires.

If the work schedule and weather will cooperate I need to jack up the rear end and check for slack/backlash in the drive line.

So barring any catastrophic rear-end explosions has anybody noticed these symptoms prior to a rear-end going out?
 

·
Super Moderator
Joined
·
11,084 Posts
The only diffs that were known to be an issue were the LSD diffs in the early 2007 base models (due to GM assembling them without the proper diff fluid additives). With a 2008 Redline, diff failures weren't common.

The classic symptoms of that were a whining noise coming from between the seats down below the "waterfall" on the back panel when reversing or turning slowly in a parking lot at full steering lock.

Try to get a better idea of where the sound is emanating from. The diff sits right between the seats directly behind the passenger compartment so if it is the diff, that's where you'd be hearing it. Otherwise, it could be related to something else. If the noise/vibration is something you've only noticed since doing the pads and rotors, it could be brake related. You can double check that work too just to be on the safe side.
 

·
Premium Member
Joined
·
552 Posts
Discussion Starter #3
Thanks!

It has been some time since doing the brake pads and I just recently started noticing this phenomenon. I also double checked the hub bolts at each wheel while I was there. All were good. I will double check the pads though.

It could be something to do with colder temps?? It does tend to go away (or at least becomes much less noticeable) after a few miles of driving. I'm just puzzled that it only does this when I am accelerating; not while coasting. Maybe something to do with mounts (motor, trans).I just can't correlate the rhythm/ cadence with something the engine is doing RPM wise. I can feel it on my foot via the gas pedal and sometimes in the steering wheel (not a shimmy just a vibration).

Maybe I just need to turn up that new Kenwood and wait till something breaks...haha
 

·
Super Moderator
Joined
·
11,084 Posts
Thanks!

It has been some time since doing the brake pads and I just recently started noticing this phenomenon. I also double checked the hub bolts at each wheel while I was there. All were good. I will double check the pads though.

It could be something to do with colder temps?? It does tend to go away (or at least becomes much less noticeable) after a few miles of driving. I'm just puzzled that it only does this when I am accelerating; not while coasting. Maybe something to do with mounts (motor, trans).I just can't correlate the rhythm/ cadence with something the engine is doing RPM wise. I can feel it on my foot via the gas pedal and sometimes in the steering wheel (not a shimmy just a vibration).

Maybe I just need to turn up that new Kenwood and wait till something breaks...haha
It COULD be an axle. They will make more noise when you accelerate than when you coast. However I don't think that has anything to do with temp changing it. I had it happen to me but that was more of a knocking type sound than humming.

What you describe though sounds like drivetrain related but after the trans since the sound changes with vehicle speed and not engine speed.
 

·
Premium Member
Joined
·
552 Posts
Discussion Starter #6 (Edited)
Thanks guys!

OK, more info; it's definitely engine related and more than likely cold start/pre-heat cycle related. I started the cold engine and after a couple of seconds rev'ed it up to 2k RPMs and held it there. The humm/vibration was present just sitting still. I then rev'ed it up to 3k and the cadence quickened and grew more intense. Just to be clear this vibration isn't something earth shattering just not exactly normal. It all but goes away after the temps reach normal operating range. After my errands I repeated the 2k hold/ 3k hold and it was not there. I have no codes but I am wondering about the VVT components. I did have the water pump changed but that was many miles ago. I would be reluctant to suspect any of the hardware/chains/ tensioners but I can't seem to remember what happened to elff's sweet white car. I think it was something timing chain related. I can't afford a Alfa Romeo replacement like he did.


EDIT: In my defense I don't normally sit there and rev the engine so I only noticed it while driving.
 
1 - 6 of 6 Posts
Top