Ok, I'm 99% sure I broke my Diff (well, If I had to guess I broke a tooth off the gear), but could It be driveshaft u-joint I

 

IMO a bad diff would be whining constantly. since you're indicating that it does not whine while in neutral "rolling" i would guess it's the tranny, not the diff.

 

I say drain the diff and check for metal bits. could certainly be the diff, if you're sure the noise is coming from behind you, not beneath you.

 

i disagree. the diff would be a constant whining noise. I would concur with the OP and say it could be the drive shaft u-joint or like i said earlier the tranny.

 

The more I think about it, the more I'm thinking cracked bearing race in something, maybe output shaft, or diff bearing race, maybe drive shaft u-joint or im hoping anyway. Its the only thing I can think of where the noise would nearly go away under load. I'm considering taking it to the dealer down the street at lunch. A Diff fluid drain and inspection is definatly going to happen tonight, but thats about as far as Im comfortable going as far as mechanical Diff work DIY.

 

vtec9 Posted on Apr 3 2007, 03:17 PM

And after the diff oil has drained for a while (with the car level) you could get underneath and look at the ring gear throug the drain hole.
Watch for drops of oil getting in your eye.
(don't ask me why I'm warning you )

I also hope you're not using any multiweight 75W-90 diff oil with 300 rwp.
A straight 90 weight (LE-607) or even a xxW-140 is better for you IMO and change it more frequent.

Change the transmission oil too while you're at it.
Look for metal shavings in the old oil as well, the transmission does not have a magnetic drain plug (OEM) the diff does btw.

Downshifting like you did puts a load on the outer (smaller) pinion bearing, as the pinion is drawn into the ring gear and may have created a bit of play / wear.

Succes!

 

Cars has never had a Diff/Tranny fuild change AFAIK. So I'm sure its running whatever fluid is OEM. But thanks for the suggestion, I'll watch for gear oil when looking through that hole plus now I know what to put back in it! (I wasn't sure If I should use Honda OEM Gear Oil or not) It only has 8000 miles on it, but I'm sure warranty is a pipe dream since its a 2003 modded all to hell, and purchased from an individual out of state.

 

But more I think about this, it doesnt make the noise when not in gear, so that rules out rear diff mostly, doesnt it? Im REALLY hoping for a U-joint behind Door #2!!

 

Well, as Spitfire and vtec9 suggested, change the diff and transmission fluids. With your low mileage this is the opportune time to change them anyways because you can get the factory fill drained and thus remove a lot of break-in metals that were suspended in the fluid. While you're doing this basic maintenance you can also check your diff for any obvious damage. You seem pretty competent so I bet this would take maybe 2 hours of your time to do both items on the car.

 

well just wanted to kick in a side note, there are no U joints or yokes on our propeller or drive shafts. your symptoms lead me to believe tranny, but you say it isnt RPM related, so it would have to be an outputshaft. Does the noise occur in neutral at any speed?