Growling/Clunking noise in rear while accelerating hard in 1st or 2nd ??

[Turninconcepts]

With the extra power I have now I can get the noise in ANY temp!

 

I am willing to try any new part, just send it this way!

 

I'll be honest - we had pushed this to one side until the weather got cooler since it seems that we wouldn't be able to get a good test platform. Now that you can do it in all temps I'll move it up in the development plans.

[LittleBlueGT]

I'll be honest - we had pushed this to one side until the weather got cooler since it seems that we wouldn't be able to get a good test platform. Now that you can do it in all temps I'll move it up in the development plans.

 

I will be waiting. I can likely do whatever testing you need.

[SeeeeeYa]

Unless I am mistaken, the parts are not available from the aftermarket yet for the LGT. As a group we do not represent a particularly lucrative developmental investment, like, for example, STis or WRXs whose focus is intrinsically performance oriented.

 

But that doesn't mean a) a solution is not possible, nor b) that a solution will never be available.

[HansGT]

As a group we do not represent a particularly lucrative developmental investment, like, for example, STis or WRXs whose focus is intrinsically performance oriented.

 

shhhh. we want them to make them anyway.

[NewScooby]

I am considering taking out my rear Diff and doing the "windshield crack filler mod" that I have read on other forums to stiffen the bushings as I can sometimes make the growl even in 80 degree weather now.

 

That or buying a new set of OEM bushings and modifying them.

 

Do any of the poly bushing companies sell cheap chunks, that we can cut down on a lathe?

[SeeeeeYa]

I am considering taking out my rear Diff and doing the "windshield crack filler mod" that I have read on other forums to stiffen the bushings as I can sometimes make the growl even in 80 degree weather now.

 

 

You don't have to take it out. Trust me. And, yes, it works.

 

While you are at it do those two forward rear lower control arm bushings.

 

Not only are the noises irritating, they are warning you. Bad things happen when drive trains are loaded and unloaded in such a manner. Destroyed my rear diff, for example. As I've said, DON'T MAKE THE NOISE.

 

In preliminary testing of the mods alluded to above I have stopped the noise. But because I'm cautious and because a lot of people's actions hinge on accurate and complete information I've kept quiet.

 

In the rear there are four bushings that are simply not up to what our modded cars can give them. I have modified them in a rudimentary way with spacers and the results are as I said, no noises. But it is still HOT out there, logging today I had 97 to 100+ IATs. That means whatever goes on now isn't necessarily what will go on when it gets cold out. But, frankly, the problem is obvious when you look. As such I don't see why the answer to that problem now won't be the answer later.

 

I'd like other people with the issues presented in this thread to make the same modifications so we can end this without more people needing diffs like I did. As far as I know I found the ONLY used diff in the US. Good sign in one way, bad if you need one.

 

Part of the noise is the driveline loading and unloading. This causes the VERY flexible bushing in the two piece driveshaft to flop around. Primarily, I believe, this is caused by the rear end with its limited slip diff to drive/spin alternately side to side. It's not hard to see why if you get under there and look at four bushings: two hold the rear of the diff to the sub frame, and two are in the forward ends of the lower control arms. These bushings are of the same construction as those many of us happily replaced in our front LCS's with poly bushings. But.........

 

The aftermarket would have no trouble coming up with better, polyeurethane, bushings for these four sloppy ones. Unfortunately, they wouldn't sell them. That's because to replace these bushings would require a dissassembly and bushing replacement beyond belief.

 

This is where true modding comes in . By using either polyeurethane as outlined in a well known online guideline alone, or as I will use it, in conjunction with a spacer, the rear should be stiffened enough to prevent problems and yet flexible enough to keep unwanted NVH to a minimum.

 

The jury is still out. I have installed the spacers and have no noise now. The 3M WS poly I just got will be installed in the next days. I can't imagine it NOT working successfully. But I am as yet unsure whether the motor mounts are a critical factor. Certainly, they are not now.

 

So, get out there under your cars and fix them! We need more data from more people who have experienced this problem.

 

Oh, this will help: http://importnut.net/motormount.htm

[NewScooby]

:icon_arroThanks, good to hear I don't need to disassemble everything!

 

I didn't start getting the growl in warm weather until I put new firmer front and rear struts on and started putting the power down much more effectively without all the squatting it was doing before.

 

BTW if anyone is interested, 3M Windshield poly available at Autozone for $14.95. I'll be putting the car on jackstands some upcoming weekend and going to town, and I'll do the two forward rear lower control arm bushings too!

[LittleBlueGT]

:icon_arroThanks, good to hear I don't need to disassemble everything!

 

I didn't start getting the growl in warm weather until I put new firmer front and rear struts on and started putting the power down much more effectively without all the squatting it was doing before.

 

BTW if anyone is interested, 3M Windshield poly available at Autozone for $14.95. I'll be putting the car on jackstands some upcoming weekend and going to town, and I'll do the two forward rear lower control arm bushings too!

 

Awaiting!

[Joon525]

Just throwing something new on the table for you guys.

 

I'll assume the 2004+ is for JDM years.

2004~Legacy Diff. Mount Support Bar

http://www.machiii.net/suspension/beatrush/subaru.htm

http://www.machiii.net/images/suspension/beatrush/Subaru/36.jpg

[LittleBlueGT]

Just throwing something new on the table for you guys.

 

I'll assume the 2004+ is for JDM years.

2004~Legacy Diff. Mount Support Bar

http://www.machiii.net/suspension/beatrush/subaru.htm

http://www.machiii.net/images/suspension/beatrush/Subaru/36.jpg

 

Nice find (also they have a real nice front "performance bar", better then Cusco but more $$s).

 

I may actually buy this piece come this winter.

[SeeeeeYa]

That rear diff pictured is not our diff. And while firming up all the bushings is necessary, the upgraded one shown is not the most responsible for allowing the rear diff to rotate. That is handled by two longitudinal studs that fit into bushings in the rear subframe. I'm not sure but I don't think the car pictured has our subframe.

 

The two studs on the rear cover of the diff, for our cars (check the vac pic data), fit into two common, floppy, bushings in the rear subframe to both locate it as well as contain its tendency to rotate. These are the bushings I have partially modified and will be finalizing shortly with the 3M poly. As it is, however, the noise is all but gone, muted and unnoticeable were I not searching for it. The filling of the entire bushing with the poly should fix those two bushings.

 

But the other two in the forward end of the rear LCA must be addressed similarly to complete the job. I have a solid PVC spacer in the rearward (most obviously worn) slot of the two in those bushings, and will fill in the rest with the 3M when I do all four bushings.

 

Again, until this is done I won't know if it will be necessary to address the engine mounts as well. From what I experience now that may not be necessary. Time will tell. However, once you look at the rear and see that it is a combination of wheel hop and oscillating traction it become obvious what the players are. This problem is as old as cars. But because of our great four wheel drive and, relatively, mild horsepower only those who have significantly increased their power to the wheels can cross that barrier and break traction.

 

It is worse when you are OVER the traction threshold but not powerful enough to really burn them, just grab/spin/grab. This is what kills parts.

[LittleBlueGT]

That rear diff pictured is not our diff. And while firming up all the bushings is necessary, the upgraded one shown is not the most responsible for allowing the rear diff to rotate. That is handled by two longitudinal studs that fit into bushings in the rear subframe. I'm not sure but I don't think the car pictured has our subframe.

 

The two studs on the rear cover of the diff, for our cars (check the vac pic data), fit into two common, floppy, bushings in the rear subframe to both locate it as well as contain its tendency to rotate. These are the bushings I have partially modified and will be finalizing shortly with the 3M poly. As it is, however, the noise is all but gone, muted and unnoticeable were I not searching for it. The filling of the entire bushing with the poly should fix those two bushings.

 

But the other two in the forward end of the rear LCA must be addressed similarly to complete the job. I have a solid PVC spacer in the rearward (most obviously worn) slot of the two in those bushings, and will fill in the rest with the 3M when I do all four bushings.

 

Again, until this is done I won't know if it will be necessary to address the engine mounts as well. From what I experience now that may not be necessary. Time will tell. However, once you look at the rear and see that it is a combination of wheel hop and oscillating traction it become obvious what the players are. This problem is as old as cars. But because of our great four wheel drive and, relatively, mild horsepower only those who have significantly increased their power to the wheels can cross that barrier and break traction.

 

It is worse when you are OVER the traction threshold but not powerful enough to really burn them, just grab/spin/grab. This is what kills parts.

 

I think you are right.

 

It is the two high mounted bushing at the back of the diff, that look like an O with a little line through it, right? They are puny and waaaay to flexible. I may try the 3M mod first seeing as it seems fairly easy.

[Joon525]

That rear diff pictured is not our diff. And while firming up all the bushings is necessary, the upgraded one shown is not the most responsible for allowing the rear diff to rotate. That is handled by two longitudinal studs that fit into bushings in the rear subframe. I'm not sure but I don't think the car pictured has our subframe.

 

The two studs on the rear cover of the diff, for our cars (check the vac pic data), fit into two common, floppy, bushings in the rear subframe to both locate it as well as contain its tendency to rotate. These are the bushings I have partially modified and will be finalizing shortly with the 3M poly. As it is, however, the noise is all but gone, muted and unnoticeable were I not searching for it. The filling of the entire bushing with the poly should fix those two bushings.

 

But the other two in the forward end of the rear LCA must be addressed similarly to complete the job. I have a solid PVC spacer in the rearward (most obviously worn) slot of the two in those bushings, and will fill in the rest with the 3M when I do all four bushings.

 

Again, until this is done I won't know if it will be necessary to address the engine mounts as well. From what I experience now that may not be necessary. Time will tell. However, once you look at the rear and see that it is a combination of wheel hop and oscillating traction it become obvious what the players are. This problem is as old as cars. But because of our great four wheel drive and, relatively, mild horsepower only those who have significantly increased their power to the wheels can cross that barrier and break traction.

 

It is worse when you are OVER the traction threshold but not powerful enough to really burn them, just grab/spin/grab. This is what kills parts.

I just checked my car and it does look like the car pictured. I do have the piece that the Beatrush product replaces as well.

I know what you're referring to in regards to the two studs on the rear cover to help stop rotation but after looking over the PDF in the "vacation pix" I think this would help as well (maybe not as much as stiffening the rear though).

 

I do think trying to fill in the stock bushings with the 3M poly is worth a shot though. I would definitely try that first as you've already started.

Good luck man! http://legacygt.com/forums/images/icons/icon14.gif

08 - Rear Differential Front Member.pdf

[LittleBlueGT]

I just checked my car and it does look like the car pictured. I do have the piece that the Beatrush product replaces as well.

I know what you're referring to in regards to the two studs on the rear cover to help stop rotation but after looking over the PDF in the "vacation pix" I think this would help as well (maybe not as much as stiffening the rear though).

 

I do think trying to fill in the stock bushings with the 3M poly is worth a shot though. I would definitely try that first as you've already started.

Good luck man! http://legacygt.com/forums/images/icons/icon14.gif

 

It looks lie the same diff to me as well.

[SeeeeeYa]

I just checked my car and it does look like the car pictured.

 

Sorry guys, there I go thinking the whole world revolves around automatic cars .

 

Yes, you're right, with the manual trans you get one rear and with the 5EAT you get another. They look different but mount the same.

 

And yes, as I said, that cross member shown with apparently poly bushings would be a nice addition. But it doesn't have those floppy ones that allow the diff to move around so much. A sort of big C clamp holds the front of the diff to that cross member.

 

But the other two bushings that hold the rear are/have become so flexible you can move the diff with little effort. Imagine what happens when over 300 lb/ft of torque gets to work. Same thing with the two rear LCA bushings. If you get close with a bright light you will see where the range of motion has worn the respective bump surfaces.

 

Interesting, the difference between the manual's rear differential and the 5EAT's. Mine has a finned aluminum rear, seemingly to dissipate heat better.

[LittleBlueGT]

Imagine what happens when over 300 lb/ft of torque gets to work.

 

or that amount multiplied by the gearbox.....so maybe 1000 ft/lbs.

[TRAC3]

any updates on this, is this the way to go? and where do I find a good description of how to fix the rear end, as this is getting louder and more prevalent in my car in any weather...

 

need to get this fixed!!

[LittleBlueGT]

I am here for updates. I hate the noise.

 

I will have to do something this winter.

[Turninconcepts]

I may have something coming in really soon that I will need someone to try. This person cannot be faint of heart, or have a lack of mechanical ability.

[LittleBlueGT]

I may have something coming in really soon that I will need someone to try. This person cannot be faint of heart, or have a lack of mechanical ability.

 

Send it to me, I will do it.

 

 

NOW!!!! JK!

 

In all seriousness I will install, take pics, and provide good feedback. I can make the noise in 80 degree weather in my car now if I want to.

 

When it is cooler outside it is just nuts! When it is -40 outside it is downright LOUD!!!

 

I can test all conditions for you.

[rony]

Seriously!!!

 

If you have a solution and need a test, let me know the details. I have access to a lift and can put it in for testing.

[LittleBlueGT]

Whatever happens, whoever tests it, let's get it done.

 

I have the noise all the time in my car, and I have access to really really cold days (-40) to confirm the part solves the problem.

 

I am also sporting a solid clutch and about 350 wtq to ensure the product gets a good test.

 

I don't really care how it happens, I just want a solid product that works.

[NewScooby]

My car is currently up on jack stands, and I filled the rear diff bushings with the 3M Windshield poly crap that comes in a caulk tube to see if that eliminates the growling noise. I call it crap because it takes a scotchbrite pad and brake cleaner to get this stuff off your skin.

 

If you try this, get some latex gloves and wear a long sleeved shirt. No pictures were taken either; I was way to dirty to pick up my camera.

 

I’m going to let the car sit for at least 24 hours before I drive it. It has been cool hear in the AM, so I will post up in a few days when I know for sure that the growl is gone. I am going to a track day next Saturday and Sunday so I went ahead and did this while I was changing out the brake pads and flushing the brake fluid.

[LittleBlueGT]

My car is currently up on jack stands, and I filled the rear diff bushings with the 3M Windshield poly crap that comes in a caulk tube to see if that eliminates the growling noise. I call it crap because it takes a scotchbrite pad and brake cleaner to get this stuff off your skin.

 

If you try this, get some latex gloves and wear a long sleeved shirt. No pictures were taken either; I was way to dirty to pick up my camera.

 

I’m going to let the car sit for at least 24 hours before I drive it. It has been cool hear in the AM, so I will post up in a few days when I know for sure that the growl is gone. I am going to a track day next Saturday and Sunday so I went ahead and did this while I was changing out the brake pads and flushing the brake fluid.

 

Good stuff!

 

We need real solutions.

 

If new bushings don't come out I will make my own eventually too.

[G.T.Subie]

It's been getting cooler here too.

 

I'm wondering if I will still here the noise now that I changed from stock/H-techs to the JDM GT Biksteins with the JDM springs. I guess I have some wishfull thinking.