My 2005 Infiniti G35 has 144,000 miles, two new rear tires and two good front tires. Sometimes, and I cannot nail down or reproduce-on-demand this situation, my car will suddenly begin to vibrate as if I’m driving over a smaller version of those rumble strips on the side of the road. The vibration continues when I take my foot off the accelerator, and will continue at a slower rate as I decelerate until I stop. Often it seems that when I come to a dead stop and accelerate again, the vibration stops, but other times it will continue as I accelerate.
But what’s really odd is other times I’ll just be cruising along and the vibration will begin, keep vibrating for a few miles, then peter out and disappear. I haven’t totally nailed down whether or not braking affects it, but if pressed I would say that I would use the brakes at least once before it disappears. Also, it only seems to begin once I hit 50-60 mph, but again, it doesn’t happen every time I go this speed. Other times this car drives incredible and makes the road feel as smooth as glass.
I haven’t taken it to the shop because I’m sure they won’t be able to reproduce it, so I’m hoping there’s someone out here that has some ideas. Thanks all!
Sounds like you have two or more tires out of balance. Vibration starts and stops as they get in and out of “phase.” Also, possibly internal tread problems with the tires.
I predict that, in time, all will be revealed… when either you get new tires or the part that is causing it falls off.
If you shift into neutral when this happens, does the noise stop or change?
Ok, got the tires balanced, didn’t fix the problem.
@lion9car: When I shift to neutral nothing changes. In fact, when I rev the engine in neutral as I’m cruising along the vibration doesn’t get any worse. But when I punch it while in gear the vibration gets much worse (this is an automatic, BTW). It actually sounds pretty rough, and I would almost say the engine sounds and feels like its running pretty ragged, but I’m not sure how that fits with the fact that I can punch it in neutral with no negative effects.
But then a mile later everything is back to normal and the car is running like a dream.
Has anyone considered the possibility that this is a problem related to the Torque Converter Lock-Up mechanism?
@VDCdriver I read up on this, and it certainly sounds like a possibility. Is this something that needs to be fixed right away, as in if it goes bonkers it could screw up my tranny?
“I haven’t taken it to the shop because I’m sure they won’t be able to reproduce it, so I’m hoping there’s someone out here that has some ideas.” - OP
As much as I appreciate your confidence in us, don’t you think the shop with a certified mechanic would be better able to isolate the cause hands-on than we strangers of unknown knowledge level can over the internet?
My thinking is harmonic dampers, maybe even motor mounts. Others here have different ideas. I’m thinking powertrain, they’re thinking drivetrain. That level of variation is normal in internet diagnosis, mainly because there’s a whole lot of different areas that can cause vibrations. But we can’t fix it from here anyway. Try a reputable independently owned and operated shop.
Well said, and noted. In fact, as I was driving around today I thought I should take it to the shop and tell them to put as many miles on it as necessary to recreate the issue.
- alignment
- tire balance
- check tires for out of round
If those are all ok, sounds like something in the driveline. Engine, transmission, drive shafts, wheel bearings.
Are the four tires the same manufacturer and model. Years ago I had two new tires installed on my wife’s 86 Dodge Colt (115/80R13). At speeds of 35-40 mph the car felt like it was going to shake itself to pieces. The two pairs of tires were from different manufacturers and even though the tire sizes matched there was a noticeable difference between the diameters of the tires. Four matching tires solved the problem. I suggest measuring the diameter of front and back tires.
On the other hand my wife’s 98 Ford Windstar came with 3 tires of one model and one replacement of a different model. It drove with no issues, but the four tires were Goodyears.
Ed B.
I’m inclined towards driveline. Driveshaft?? Or differential maybe? This sounds like a case of RWD driveline problem. Either the rear u-loint (or-CV, not sure what a G35 has) is failing or dried out of lube or possibly the pinion bearing has gotten a bit loose. A good driveline guy should be able to figure it out pretty quickly with your description and a test drive.
I’m with Mustangman on this one. Just so you don’t think i’m another kook throwing random possibilities around. I have 40 years experience in the automotive repair industry and a damn good track record in diagnostics weather it be steering/suspension and alignment.Drive train/power train.And even tire related issues.First off the tires are ruled out.Why? Because if it was a tire or balance issue it would not be intermittent It would be there every time you drove the car at the noted speeds.PERIOD! I also rule out an alignment issue because the alignment being out of specs may create a stability and or a control issue but not an intermittent vibration anywhere on the vehicle. It would be every bit as consistent as a bad tire or a balance issue. But now lets add a carrier/center support bearing into the equation. You have a rear wheel drive vehicle with an intermittent vibration that kicks in somewhere between say 50-70 MPH. If you are hearing/feeling a popping/knocking sound around the center of the car along with a vibration which can range from mild to wild at any given time that is constant when your speed does not change, but changes as you accelerate or decelerate it may well be a driveshaft carrier bearing,(AKA) Driveshaft Center Support Bearing. Which are used to support the center where a two piece driveshaft comes together in the middle.
And this person has probably solved their problem after 3 years.
Wow, I’m both amused and shocked that someone actually replied 3 years later. It took me minute to even remember what this issue was (I sold the car a year ago).
FWIW, I believe the problem was a stuck brake caliper on one of the rear wheels. I don’t know why the vibration only occurred at that speed, but I had the calipers and brake lines replaced, and the problem went away.
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Thanks for the follow-up OP. Goes to show internet car repair diagnosis leaves a lot to be desired compared to an actual mechanic looking at the actual car in their shop. Nobody here even mentioned brakes as far that I can see.
Thanks OP! This exact same thing just started happening to my 2002 Toyota Highlander this week, and I was at a loss. Cheers 
thanks for the help, i got the same issue and somehow it was the hand-break break was stuck and rusted.