Hello everyone. Recently I have just changed both my rear axles and both rear wheel bearings . I have an 06 g35 coupe , and I upgraded to the z1 Motorsports 370z axle and bearing kit that can fit on g35s . After the install my steering wheel and for the most part the cabin will vibrate when I’m going 45-60 mph and it did not do that before . My wheels are balanced so Ik it’s not that . I also hear a humming noise while just cruising . I havent done an alignment on it yet but I’m not so sure if bad alignment will cause vibrations . If anyone has done the install or has had these issue lmk . Thanks for the help

 

I have done that upgrade and no there were no issues.

Put the car on jackstands, get open ended lugnuts and install them directly on the rotors without the wheels installed. You will need to use washers to shim up a tiny bit.

With the car on jackstands drive up to the same speed and see if the vibration is still present, this will either confirm or rule out the driveline/axles as being the issue. Be aware the engine revs INSANELY fast without the tires on up in the air like that, very easy to hit the rev-limiter, you can pretty much just start in 4th gear, no need to go 1-2-3-4.

If the vibration is not present then it's somewhere else in the car either wheel/tire or somewhere in the front.

You will probably find something not torqued properly while tearing it all apart.

 

had exactly the same issues.. was coming home the other day and barely made it back. Started with the whining between 45-60mph...
changed out the wheel bearing hub assemblies. Got back on the road. 1 week later, I"m in stop and go traffic crawling... and I'm hearing a cyclical grinding from the rear. Thinking it's the diff... Now I'm taking the CV Axles off again.. Put the car in gear and "clunk" in reverse and :clunk: ..
12 miles to go and a horrible loping grinding sound of metal.. couldn't go over 40 without feeling safe.. Horrible.

Now I'm considering: alignment issues causing brand new upgraded parts to go bad so quickly?
Everything is torqued correctly. and this is the second time I've tried and failed on cv axles.. Surely it can't be that difficult.

 

Get the car up on jackstands and find out what the culprit is, might not be the axles.

Read my previous post about driving the car while up on 4 jackstands. You can also unbolt the CV axles and let them hang separated from the diff to isolate the issue further.

 

good advice. I'll likely do just that when I swap out the diff.
Something back there made a loud crunch when put into gear.
Just moving by hand the Differential is pretty Loud and cranky.
The dif is from an 04 has about 100K miles on it by now..
Originally i took the stock diff out to upgrade,
looks like that day has finally come..
Prolly put the original back on and use the blown as a core to upgrade.. suggestions?

 

You can always drain the fluid out of the diff and see if it's full of glitter, if it's still clean then just pump it right back in.

Definitely keep troubleshooting until you find the culprit though.

 

good tip on the Diff Fluid. thanks for that.
Have done lots more research and realized it was the driveshaft.
I originally diagnosed that when I got the car some 7 years ago (un-serviceable U-joints and two piece driveshaft lasted 170K. I got lucky it just gave me a bunch of racket and didn't fly off... lol)
Went with Concept Z single Driveshaft with Foam (for noise dampening)
Main reason: serviceable u-joints
Bonus: half the weight and better throttle response.

 

i had same issue.. whining noise between 45 and 60 mph
vibration ended up being the drive shaft.
replaced that and still hear the whine but the car feels solid.

 

Keep in mind that gearboxes and differentials are noisy. The G was pretty light on sound deadening insulation through the transmission tunnel so you WILL hear both those components at certain speeds, usually the higher the speed the noisier the gear.

 

yeah, I’m starting to understand a lot more with every modification.
not every part is going to be spectacular and often time minor modifications may be needed when installing upgraded parts.
par for the course I figure.
I I’ll say, the driveshaft did last 170,000 miles. It’s now a floppy POS. Very happy it’s the new single shaft. Very! It’s also nice to have new cv axles as well.
the ole ‘03 never drove this good!! Thing is on rails.
having the biggest urge to get new wheels now. 😁

 

I have the same issue. I did the upgrade alongside new wheels/tires, adjustable control arms and a fresh alignment. It's either time for a new alignment or I'm going to have to do what cleric670 suggested (jackstands).

 

have you looked into putting collar/inserts for the rear subframe bushings? My 03 G35 vibrated with every mod until I stiffened up the subframe.
now its all kinds of smooth.

 

I put the car on jack stands, removed the wheels and snugged down on the lugs. Without the wheels I'm still getting the vibration coming from the same rear passenger side. I did notice that the rotor hat looked as if it had a bit of very slight off-axis movement. I put the wheels back on because I needed the car today but I'll investigate further. I'm leaning towards ordering some new bearings even though the ones I have on only have about 12k miles on them (same as cv axles).

Whutch1 mentioned subframe bushing collars. I do have those, though I suspect it makes the vibration more, not less pronounced — not sure. When driving at 60mph, the vibration causes my trunk lid to vibrate.

 

If this vibration did NOT exist prior to your repairs then I would take everything apart again and look for something obviously wrong or missed.

 

It turns out that I had a chip in the inside edge of my rotor. These are the two-piece rotors from z1.