Bad diff bearing or axle. SOLVED.
 

2005 Civic, MT, 120k

So after a couple days of troubleshooting I'm pretty sure the left diff bearing is what's causing the humming noise I've experienced for the past week. The humming is def coming from the tranny.

If I took the axle out would I be able to easily tell if the diff bearing is bad w/out pulling the tranny?

It's either that or the left inner axle joint. It is the original axle and I delivered pizza's for 5 years in this car so it's had a difficult life. Boots are fine and I see no signs of leaking.

Here's the wild card, I've had a broken front/tranny mount for a couple months. They're not totally twisted like some pic's I've seen but there is a cut that goes through one of the rubber supports. You can't even tell they're broken unless you move the motor around to see the gap open up.

Would broken motor mounts cause the inner axle to go bad or the diff bearings?

If I do need a rebuild should I take it to a local shop or snag one of those synchrotech trannys off ebay? Or perhaps get a junkyard tranny?

Front mount crack shouldn't cause diff bearing issue and diff bearing RARELY goes bad. Humming noise can be your wheel bearing or tire noise, but should investigate more.

Why do you think it your diff bearing ?? diff bearing is inside your tranny, can't see it just by pulling you axle off, you'll need to open up your tranny.

I jacked the car up, put it on jack stands, started it up and put it in 5th gear. Noise continues so it's not tire noise, that's exactly what it sounds and acts like though.

So I isolated each side by jacking up one side, starting it up and get the tire spinning. It makes the noise when the left tire is off the ground, not right. At this point I figured LF wheel bearing.

The hum is VERY noticeable in the cabin however when I get out and stand next to the LF wheel while it's spinning I can't hear it at all. You figure if it was a wheel bearing I'd be able to hear it.

So my only other thought would be the LF axle? Would that cause a hum? Boots are fine, show no signs of leakage. Car has had 5 years of delivering in the city so it's had a rough life. Maybe I just wore out the axle?

I got under the car and looked at the LF inner joint very closely. 1st thing I noticed at the very end of the joint, closest to the tranny, is black, like it got too hot. 2nd it seems like there's very fine metal shavings around the inboard joint, the metal end of the axle. I cannot move the axle up or down, only in and out.

have you check your tranny fluid?? or change it??

Tranny is full.

I had been getting my tranny flushed at jiffy lube. A few months ago I did it myself and used Honda MTF. Shoftly after that I noticed gear noise, most noticeable in 1st and 2nd but I think all gears make the noise. It seems to go away when I get over 2k rpms.

Now I have this.

I've heard about people having problems with trannies after flushes....maybe that's what did it.

ok.. on the noise, when u step in the clutch does it make noise?? and when you driving/rolling and step in the clutch, does it make noise or the noise goes away went step on clutch or the other way around.

Doesn't matter if the clutch is in or out, noise is always there. Gets faster and slower with speed.

It does get more intense when I turn right.

so you hear noise only when rolling? or at stand still too??

Only when I'm rolling.

Most likely not your tranny, possible belt area, look at tensioner, brake system, timing belt change??

Oh didn't read that when you turn it make humming/whining noise too?? check your power steering fluid for possible air in the system.

Did you have your car service before this issues??