2007 Tahoe 5.3L 4WD vibration while accelerating
 

Hi All, my hoe vibrates as I accelerate, at any and all speeds. If I take my foot off the accelerator the vibration is completely gone. This is not a tire or tire balance issue.

I just replaced two coils and associated plugs on cylinders 1 & 6 today since I knew I had these couple of coils going bad (code 300 intermittent misfire and tested with oscilloscope). I found it a strange coincidence when the guy at the dealer ship told me he had to replace the exact same 2 coils in other 5.3L's??? I thought the vibration might have been caused by the misfire. If I am driving and put it in neutral I can rev the engine, no vibration. If i'm stopped and put my foot on the brake and rev engine, no vibration.

It seems to be related to the drive train only while accelerating? But I checked the universals and they seem fine.

Sometimes there's a noticeable clunk or loud click when I engage reverse. I loosened the drain screw on the transfer case and the lube began to flow out so I assume there's enough in there but not sure.

I jacked up the entire rear end and turned the wheels, never noticed anything strange.

Like I said with my foot off the gas the vehicle drives very smooth, around turns, while braking, etc...no problem. I do get a couple of messages on the dash computer sometimes: "Service Stabilitrak", and "Check 4 WD" or something along those lines, especially if I'm parked for some minutes...I hope it's not related to that stuff...sounds expensive and not something I can probably fix myself.

If no one's sure, how can I further test the issue?

Thanks!!

Just a hunch, but I'm thinking U-Joints, that clunk in reverse sorta says that too. Get under it again, do each one, shake it up and down, then turn the shafts 90 deg and shake um again. Gotta be in there somewhere. Do you U-Joints have Zerts in them, might give um a shot of grease and see what happens.

Thanks swhouston, I jacked up the entire rear end, both wheels off the ground so I could spin the wheels. Then I got up under and turned/pulled the drive shafts front and rear by hand and they're smooth. I also noticed the counter weight on the rear shaft so that didn't fall off. I could hear the gearing inside the transfer case when I turned the shafts so I checked the oil in it by loosening the drain plug and some oil leaked out but I have no idea really how to check how much oil's in there other than drain it all out, not even sure if low oil in the transfer case could be the problem, there are no signs of a leak. I don't think it's U-Joints after the checks I did on them like you said, rotate 90deg push pull, but it could still be like you said. I never noticed any grease nipples. Could be a case where I have to wait for something to break completely before I find the problem? Any other ideas?

Thanks!

Don't quote me on it, but it seems like I recall something about the flex plate being cracked that could cause vibrations?:confused:
Just thought I'd mention it, could be completely off base...

Thanks in2pro, what/where is the flex plate on the tahoe?
Thanks!!

Flex plate, formally known as the flywheel... also might want to check your motor and transmission mounts for cracks or tears...

OK, thanks again, however can you tell me how I would be able to check the flywheel? Isn't that enclosed?

On manuals, there's a removable dust shield on the lower part of the bell housing. Not sure about these autos. My GTO had access as I had to tighten the bolts holding the flex plate to the crank. Made a clunking sound at idle.

Did you ever find problem? my Tahoe is doing the exact same thing. It vibrates the worse when foots barely on pedal. Any help to the issue would be appreciated.

Thanks
Brandon

Hi yes it turned out to be the front to left drive axel assy. It comes as one piece refurbished for $250. I replaced it myself, need 26mm socket and a new control arm bushing with bolt. Not too big a job, if that's the same issue your having. I could only figure it out by really hanging out the Window and listening. First I thought wheel bearing until I took it apart.