Just bought a 2008 fit with a manual transmission with what I thought were bad wheel bearings. It makes a loud humming noise like bad wheel bearings do from 20-85 peaking at 40mph. I replaced the wheel bearings and that did not fix this. I raised the front wheels off the ground and put it in 5th and let it turn the wheels 20mph at idle. The noise was the same with the wheels off the ground and is not audible outside the car, only in the car. It doesn’t matter if the clutch is in or out or if the car is in gear or not, it happens when the wheels are rolling. It also does not seem brake related as the noise does not change when the brakes are pressed and no vibration in the pedal. Could this be the differential or maybe axle bearings in the transmission? Can post a video of sound if necessary, but basically it sounds exactly like a bad wheel bearing, but it’s not.

 

If the fault were in the transmission I'd expect it to change with gear changes, having to build up again in each gear, yuh know? But honestly I don't know transmissions, nor have I heard of any trouble with this one. No trouble with clutch behavior?..

And did you do the wheel bearings yourself?
If the sound grows/changes consistently with speed regardless of gear, we'd have to be looking at either the wheel hub or, i guess, where the cv shafts interact with the trans. I'd sooner redo wheel bearings a second time and make sure they're perfect and not overly-compressed. I'm a little thrown by the sound only being noticed in the cab though. How's your MTF look? No shavings or anything, right?

😅 Sorry for my writing style. A lot of questions far apart. hard to respond to.

 

when I tested with the wheels off the ground the first time I had both wheels off the ground and the differential chose to spin the driver side, so I did it with only the passenger side off the ground and the sound went away. So it was coming from driver side wheel. Also have had an abs warning light since the bearing job and I accidentally dropped the caliper once so I thought I just damaged the abs sensor. Turns out I was supposed to remove the sensor before doing the bearing… oops. Have never worked on a front wheel drive car w/ abs. At this point I assumed the sensor was crushed and toasted the bearing. I replaced the driver side bearing and the bearing wasn’t scarred or anything when I took it out. test drove it and the noise is still there, so I wasted another $40 on a bearing. It’s identical to before. I pressed the new bearing in with a disc the exact size of the outer race so I don’t think it could have been damaged on the install. I used a wrench on the press and stopped when it got harder to turn. Axle nut was tightened to the exact same spot as before. I don’t think it would be possible for it to be the transmission since it’s only on one side but I’m not familiar with how the differential and transmission work on these cars. Is the mtf what also lubes the axle outputs on the diff?

 

The MTF lubes everything. diff is internal. So when you drain your MTF, if there's some damage, you may be able to find debris. That would give is a hint, but if there's nothing I'd dive back into that hub assy.

knowing you did the job yourself, there's nothing you feel uncomfortable with? Man, if I could drive it I'd have some better input..
Don't feel bad for swapping the bearing though. That was essential to diagnostics. A pain in the butt, but it's what everyone would have said.

There aren't any differences you noticed between your two hubs, are there? It may be like, strange input, but ive seen a bearing nstalled without a snap ring once. that's kinda stupid given your description. The abs thing shouldnt matter..

Maybe I can take my drivers front wheel off and take some pics later. and of the cv shaft entering the trans. if you'd do the same we can compare 'em. Get the brake caliper, pads, and even the wheel.

 

So I pulled the cv shaft and ran it for a few seconds in 5th gear on the jack stands and the noise was gone, so it has to either be the hub or cv shaft. I’ve also tested with the caliper off and it was still there so I know it’s not brakes. I’m pretty confident I did the bearing correctly w snap ring etc especially since there are no issues with the other side, but just in case I ordered another timken bearing and a drivers cv shaft. Going to replace the cv and test and if that doesn’t work then I’ll do the bearing again and film it lol, 3rd times the charm right?

 

All the components, hub shaft brakes etc seem normal. No play on the bearing, no clicking on the cv shaft. I have not drained the mtf yet because I haven’t gotten a chance to pick up some Honda mtf yet

 

Hold up. Do you have original CV shafts, and was the car ever in a rusty area? this is a longshot.. but the oem cv shafts got recalled for rust forming hidden under an insulator.. That'd be on the passenger side though, wouldn't it? I dont see how that could cause your fault, but admittedly I'd be all kinds of interested if it did.

Also. You drove the car in 5th with no cv shaft? shouldn't the mtf have poured out?.. That's pretty ballsy 😂 I wouldn't have thought of that.
Timken bearing. I like this guy.

 

The car has been in Austin TX all it’s life, so no rust. Not sure on the age of the CV’s.

I had just the front driver raised overnight so I think a lot of the mtf was on the other side. I tested it for a few seconds in 1st and there was no fluid on the ground. Only had it in 5th long enough for the front driver cv output to spin to 25 mph for a split second to know there was no noise and then shut it off. Probably lost like a 1/4 cup of mtf after being in 5th with the open shaft. new CV shaft comes in today, I’ll update after.

 

You'd tell me if your old CV boots had goop on 'em indicating a rip, right?
Lookin forward to the update, and appreciative of the trick you shared. Thank you.

 

did you ever find what the problem is? my vehicle is doing the same thing. I replaced the bearings because of the noise, and it still makes the noise, starting around 40 MPH and getting louder the faster i go. the sound goes away when the speed goes below 40.

 

I had this for awhile too... It seemed to be related to tire pressure in my case, or perhaps a particular set of tires combined with tire pressure. When I would run 39+ cold PSI, this would occur, a kind of thrumming/hum. It wasn't relating to loading up the bearings on one side; i.e. cornering at speed. After experimenting with reducing cold tire pressure to around 32-34 PSI, it vanished, and now all is quiet again.