Grinding/Howling noise while coasting

[COdsm]

So lately I've noticed when coasting at about 30-40 in 3rd and 4th there is a howling/grinding noise from the rear. It's not extremely violent, but it can be heard. It doesn't happen in neutral or any other gear. My best guess from doing research is its the rear diff bushings. My other question is how harmful is it to the car? Or is it more just an annoyance?

 

[SrKegler]

Rear diff problems wouldn't be gear dependent. Since you said under deceleration in 3 or 4, I wonder if its one of the carrier bearings. Just throwing a wild guess out therr

 

[Crash429]

Are 3rd and 4th gear on the same shaft in the transmission? Of they are could be a bearing going out on the of the shaft, is there any grinding when up or down shifting between 3rd and 4th if there is could also be a synchronizer, goodluck let us no what u findout

 

[spook302]

I believe first and third and 2nd and forth with reverse and 5th sharing shafts. No noise in 5th gear? I rebuild differentials often as well as regear and lockers. Does the noise change pitch when going on and off throttle? Carrier bearings and pinion bearings will do that when pitted. Usually almost always a single bearing in the diff. I'd start with draining some fluid out of the drain hole. Just enough to see what color it is and if there is any signs of metal debri inside, like metal flake in the fluid. I have seen straight grey metallic lube come out of some that where driven to long on. A bad pinion bearing will sometimes have a pinion seal leaking if its loose because the bearing deteriorated. I'd start there. It could be a drued out u joint squeaking or a center support bearing as well. There are the four rear inner and outer wheel bearings as well. Keep all the in mind when you drive it next. Try and decide if its coming more from the right rear or the left rear. The direct rear center or under the seat. That will help you decide where to investigate. I like to lean and get my head right over the center console so I'm in the middle of the vehicle while listening. It helps get an equal approach.

 

[COdsm]

Rear diff problems wouldn't be gear dependent. Since you said under deceleration in 3 or 4, I wonder if its one of the carrier bearings. Just throwing a wild guess out therr

My guess is its more speed dependant, I just happen to be in those gears at that speed.

is there any grinding when up or down shifting between 3rd and 4th if there is could also be a synchronizer, goodluck let us no what u findout

I'm fairly confident its not the trans, as it is not showing other symptoms of it being trans problems.

I believe first and third and 2nd and forth with reverse and 5th sharing shafts. No noise in 5th gear? I rebuild differentials often as well as regear and lockers. Does the noise change pitch when going on and off throttle? Carrier bearings and pinion bearings will do that when pitted. Usually almost always a single bearing in the diff. I'd start with draining some fluid out of the drain hole. Just enough to see what color it is and if there is any signs of metal debri inside, like metal flake in the fluid. I have seen straight grey metallic lube come out of some that where driven to long on. A bad pinion bearing will sometimes have a pinion seal leaking if its loose because the bearing deteriorated. I'd start there. It could be a drued out u joint squeaking or a center support bearing as well. There are the four rear inner and outer wheel bearings as well. Keep all the in mind when you drive it next. Try and decide if its coming more from the right rear or the left rear. The direct rear center or under the seat. That will help you decide where to investigate. I like to lean and get my head right over the center console so I'm in the middle of the vehicle while listening. It helps get an equal approach.

As soon as I get on the gas the noise goes away, it only happens when I let off completely. I'll start there and let you know, thanks for the suggestions, I'll keep a close ear on the sounds.

 

[AWDPetmitsu]

Was your car ever towed with two wheels on the ground?

 

[5150DSM]

As soon as I get on the gas the noise goes away, it only happens when I let off completely. I'll start there and let you know, thanks for the suggestions, I'll keep a close ear on the sounds.

Are you sure it's not a wheel bearing. Car noise under acceleration may be masking the sound so you only hear it coasting.

 

[poteau]

My evo 1 has the same issue. I ripped apart the rear diff looking for the issue.
Check out this post:

http://www.dsmtuners.com/forums/art...rear-differential-inspection-replacement.html

He ripped apart the rear diff and found nothing as well.

I contacted shep trans today regarding this issue and after talking to John, he told me that it's clutch and harmonic related due to aftermarket clutch and the only way to fix it is to go to OEM. John said people just learn to deal with it and it's nothing major.

I am not sure how convinced I am with this, I want to take apart the PTU to see if there is anything there that can be wrong.

 

[TSImuchforyou]

Yeah I would go with wheel bearing.....just replaced mine and it sounded just like your issue also thought might be carrier bearing on the driveline.

 

[97blkeclipse]

Wheel bearings or carrier bearings would be my guess.