[wrx.jordy]

So i recently purchased a 2004 wrx about a month or two ago and recent i’ve had this really hard clunk that feels like it’s coming from the bottom of the car. It does NOT happen when the car is coasting with my foot off the gas but as soon as i put my foot on the gas to accelerate it starts to have little clunks. The really hard clunks happen when i’m going at slower speeds and when i have my steering wheel turned over to either side all the way and give it some gas the car will even jerk a bit when the clunk happens. I’ve taken it to many places and everyone has given me a different answer. The dealer said it was most likely the center diff but i have also replaced the cv axles and motor mounts but that didn’t do anything there is also a low whining that happens when i’m in higher speeds these both started happening at the same time.
im open to any ideas really stressed trying to figure out what’s wrong with this car everyone’s telling me to sell it but i just can’t love this car too much for the short time i’ve had it.

 

[XJman]

Go under there and grab the driveshaft at either end and wiggle it. There should be zero movement at the joints.

 

[wrx.jordy]

Go under there and grab the driveshaft at either end and wiggle it. There should be zero movement at the joints.

just checked there wasn’t any play at all

 

[XJman]

The other thing I would check that won't be grossly expensive would be the struts. It wouldn't explain the whine, but that may be unrelated.

On a side note, have you changed the gear oil lately?

 

[wrx.jordy]

The other thing I would check that won't be grossly expensive would be the struts. It wouldn't explain the whine, but that may be unrelated.

On a side note, have you changed the gear oil lately?

i haven’t changed the gear oil and i was going to change all the fluids but then i started having the clunking sound. Do you think it could really be the viscous coupling/center diff ? i’ll take a look at the struts

 

[XJman]

Could be I'm just trying to run through things to check that don't require disassembly of the entire car to fix as to hopefully find a more common and cheaper problem

 

[wrx.jordy]

Could be I'm just trying to run through things to check that don't require disassembly of the entire car to fix as to hopefully find a more common and cheaper problem

i also don’t see anything out of the ordinary with my struts

 

[Tarzelus]

Do those models have a center bearing in the driveshaft? What you describe to me sounds like a toasted midshift bearing allowing the driveshaft to move up and down under load. I've seen that a lot on multi-piece driveshafts.

 

[wrx.jordy]

Do those models have a center bearing in the driveshaft? What you describe to me sounds like a toasted midshift bearing allowing the driveshaft to move up and down under load. I've seen that a lot on multi-piece driveshafts.

i actually don’t know is there a way to check ?

 

[Tarzelus]

Yes, there should be a big loopy thing around the driveshaft about half way between the trans and rear diff if there is one. It's not often I work on Subarus and only got mine last Saturday so I'm not super familiar with these drivetrains yet, so please pardon my ignorance if they don't even have them at all..

 

[Tarzelus]

I just looked at my car and it has one. Hard to see when the car is on the ground but I spotted it from under the rear bumper

 

[wrx.jordy]

I just looked at my car and it has one. Hard to see when the car is on the ground but I spotted it from under the rear bumper

and if my car has one is there any way to tell if it’s bad? not home rn so i can’t look but i will when i am

 

[Tarzelus]

If it's as bad as I think it would be per your description you should be able to grab the shaft at either side of the bearing assembly, as opposed to either end, and mostly recreate the noise just by giving a good wiggle. There will be a lot of slop. If it's good it should just feel like the driveshaft is supported in the center by a piece of rubber (cuz it kinda is, soaks up driveline vibes).

Otherwise I've lifted cars/trucks enough to get all 4s off the ground, put it in gear and get the wheels spinning a decent pace (20-30mph is usually enough) and carefully put a hand on the bearing housing/stethoscope the housing to feel/listen for noise. Sometimes in this situation you can see the issue without having to feel or listen as the shaft will be moving erratically. The last one I did ('10 Explorer Sport-trac) didn't have any in-cabin indication until it was driven a few miles. The hotter it got the looser it sounded.

However.. if the dealer checked it out and didn't find this, I would be pretty surprised. Maybe. I've seen some real WTF stuff come straight outta dealerships. I personally know a guy that works at my local Subaru/VW/Volvo dealer and I wouldn't let him touch my car with a 10 foot pole.

 

[wrx.jordy]

If it's as bad as I think it would be per your description you should be able to grab the shaft at either side of the bearing assembly, as opposed to either end, and mostly recreate the noise just by giving a good wiggle. There will be a lot of slop. If it's good it should just feel like the driveshaft is supported in the center by a piece of rubber (cuz it kinda is, soaks up driveline vibes).

Otherwise I've lifted cars/trucks enough to get all 4s off the ground, put it in gear and get the wheels spinning a decent pace (20-30mph is usually enough) and carefully put a hand on the bearing housing/stethoscope the housing to feel/listen for noise. Sometimes in this situation you can see the issue without having to feel or listen as the shaft will be moving erratically. The last one I did ('10 Explorer Sport-trac) didn't have any in-cabin indication until it was driven a few miles. The hotter it got the looser it sounded.

However.. if the dealer checked it out and didn't find this, I would be pretty surprised. Maybe. I've seen some real WTF stuff come straight outta dealerships. I personally know a guy that works at my local Subaru/VW/Volvo dealer and I wouldn't let him touch my car with a 10 foot pole.

if it was that wouldn’t the noise be constant tho? the noise doesn’t always happen but it happens enough and hard enough to where it makes the car pretty much undrivable

 

[wrx.jordy]

if it was that wouldn’t the noise be constant tho? the noise doesn’t always happen but it happens enough and hard enough to where it makes the car pretty much undrivable

often enough*

 

[Tarzelus]

Not necessarily. It's possible with a smaller diameter driveshaft with smaller less articulative u joints (compared to the trucks I'm used to seeing) to spin fairly true until opposing forces are put on it like say torque from throttle or a parking situation where there is the typical difference in rotation between axles and individual wheels and what I like to call "driveline bind".
Driveline bind is basically the front and rear diffs fighting each other thru the driveshaft and transmission. Add in some torque to the differential and a poorly supported rear shaft wants to flex and bend wherever it can, namely the center u joints at the bearing on a multi-piece shaft.

Under deceleration/coasting they usually smooth out because there isn't really any torque being applied - the rear diff is trying to slow the shaft but the viscous coupler in the back of the trans allows enough slippage that the shaft isn't trying to twist away.

Hope I made that understandable.. People often tell me to speak english

 

[wrx.jordy]

Not necessarily. It's possible with a smaller diameter driveshaft with smaller less articulative u joints (compared to the trucks I'm used to seeing) to spin fairly true until opposing forces are put on it like say torque from throttle or a parking situation where there is the typical difference in rotation between axles and individual wheels and what I like to call "driveline bind".
Driveline bind is basically the front and rear diffs fighting each other thru the driveshaft and transmission. Add in some torque to the differential and a poorly supported rear shaft wants to flex and bend wherever it can, namely the center u joints at the bearing on a multi-piece shaft.

Under deceleration/coasting they usually smooth out because there isn't really any torque being applied - the rear diff is trying to slow the shaft but the viscous coupler in the back of the trans allows enough slippage that the shaft isn't trying to twist away.

Hope I made that understandable.. People often tell me to speak english

i’ll have to double check my drive shaft but yesterday i wiggled it and it didn’t seem to have any movement and much less be able to recreate the noise

 

[Tarzelus]

It may be worth noting to not have any stress on the shaft when checking it, i.e. rear wheels off the ground and trans in neutral. If there is stress on the shaft the movement will have already been taken up and you won't be able to oppose the force on the shaft enough to feel the movement. This goes for the u joints and center bearing both.

Hope this helps, and curious to hear what resolves your issue. Please post when you get it figured out

 

[wrx.jordy]

It may be worth noting to not have any stress on the shaft when checking it, i.e. rear wheels off the ground and trans in neutral. If there is stress on the shaft the movement will have already been taken up and you won't be able to oppose the force on the shaft enough to feel the movement. This goes for the u joints and center bearing both.

Hope this helps, and curious to hear what resolves your issue. Please post when you get it figured out

for sure will i’ll be taking apart my center diff soon and while i’m at i’m gonna check a few other things. i’ll post once i figure out my problem just gonna pray and hope the dealer was right