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Discussion Starter · #1 ·
HI All, just wondering if someone might have a wild guess what to look at here: car is making a groaning/vibration (or maybe rubbing?) sound when turning left. It seems to be coming from the front. I haven't had a chance to really look at it; car is at shop today (for new Torsen diff) and they are going to take a look at it.

Sound happens when turning left and when straightening our after a left turn. It's sort of a groan or vibration; doesn't sound like something rubbing to me, but it could be.

Car has been sitting all winter. 2010 GT with 105K miles on it. Last year I replaced lower control arm bushings, ball joints, struts, springs, upper strut mounts. I had a trouble accessing some of the bolts for torque wrench and might not have torqued everything just right. Before taking to shop I retorqued the front LCA bolts as best I could; which I found a little loose. Ball joints were greased when I installed them; wonder if they need more?

I do have brake cooling ducts, which I installed last year, and need to be re-routed a little because the driver side rubs on a full-lock right-turn. I don't think this is it; the sound is different, plus it happens when turning the other way.

Brake pads are track pads, left over from track days last year. Since the car hasn't been driven much since sitting, they are squealing a bit; wonder if they might be making the groan somehow?

I know this is pretty vague, hard to diagnose over the interwebs, but any thoughts, guesses, suggestions appreciated.

Will report back later . . . thanks in advance
 

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There is a foam or plastic panel that closes up the front fenders at the door hinge side. They are friction fit and sometimes come loose.
 
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Maybe:
 

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Discussion Starter · #4 ·
thanks for the ideas . . . if it is the diff, it should be cured by the new Torsen that is going in today . . . I am actually not sure it was coming from the front, and that thread has some ideas on how to narrow it down later, if it is still there
 
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I had a groan a little while after changing struts (dismounted springs). It was my daily driver then, and I found out quickly it got worse sounding and more consistent as I drove each day. I put some witness marks on the top nuts for the front struts and found that the top nut on one side was backing off! :oops: I had torqued the nut to appropriate torque setting and it was a nylon lock nut, but it still backed off. I re-torqued the nut, but it came loose again.

I am not one to use an impact wrench for tightening things down, but I ended up using an impact wrench to carefully synch down the nut (making sure not to spin the strut shaft) and remarked the witness mark. Hasn't backed off 40k miles later and the witness marks are intact, though a little dusty. :D

You mentioned you did struts and springs last year, so you might check if this is happening.
 
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Discussion Starter · #6 ·
thanks, yes that strut nut is definitely a possibility also . . . I had the same difficulty with no good way to torque that thing down
 

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You are welcome. Also, just to add, the noise I had occurred on a single steering direction too (I think left). Both nuts moved tighter when I used the impact wrench, so I can't see exactly which strut it was that had backed off. However, I do see that the driver's side strut top nut had tightened more than the passenger side; if I had to surmise, it was the left, driver's side that had loosened and caused the noise on left hand turns for me.
 

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Discussion Starter · #8 ·
Hi All -- thanks again for the suggestions. It turns out, we think, that the sound is caused by the rear brake pads; they are worn down almost to the backing plate and/or the calipers are a little stuck. I never heard brakes make a noise like this before; but the shop that did my differential thinks it is caused by the rear end shifting slightly during the left turn and the backing plate is rubbing and/or the caliper is sticking. I do check my pads regularly, usually before track days; last time I checked (before my last track day) they were getting a little low but I thought I had plenty left. Apparently I ate up more pad in those sessions than I expected.

The shop also suggested that I replace the calipers while I'm at it; since they are fairly cheap and they could be sticking. I think I will look into a rear caliper upgrade; but last time I checked there was nothing available, other than an entire rear big brake kit, which I don't really need.

I did ask the shop to torque the upper strut nuts; they said that they did and they were pretty close already. They can be torqued with an open-end torque wrench attachment (which I don't have) while holding the top of the shaft with another wrench. I think I will mark them to check that they are staying put, like SVT suggested.

I'll report back when it is fully cured.
 

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The shop also suggested that I replace the calipers while I'm at it; since they are fairly cheap and they could be sticking. I think I will look into a rear caliper upgrade; but last time I checked there was nothing available, other than an entire rear big brake kit, which I don't really need.
That is a suggestion, but not sure if I would take the replacement. Most calipers are reman or off-brand, which you don't know the longevity of. I would not run off-brand calipers if you are doing track events. Stay with the original Motorcraft ones. As for big brake kit, don't do it on the rear. Even the '12-'13 Boss 302 have the brake size and caliper you have (though a slight modification on the casting); same brake pad and rotor. If you go to a bigger diameter rotor/caliper setup in the rear, the knock back on the track driving will become more noticeable due to how the axle shifts in and out of the housing on turns, as you mentioned.

The new Torsen you mentioned should take up a good deal of that slack and now that you don't have clutch plates that wear down, that slack will be consistent, but there is still slack or slop in the shafts even on the Boss 302 LS with the Torsen. Also, most big brake kits are a fixed caliper design which is not what you want on the axle that slides in a out; the OEM calipers with slide pins are more forgiving with an axle that slides in and out on turns.

For possible caliper sticking, you can extend the rear pistons without the pads (care not to over extend so much the piston comes out of the bore), remove the dust boot, clean the dust boot with water and some mild detergent, and then clean the piston surface. Before putting the boot back on, use the caliper windback tool to return the piston inside the bore all the way then extend again with the brake pedal. Look for any particles or fragments from the inner seal. If you see shredded rubber fragments or excessive brake fluid accumulation on the piston, then you might be looking at a replacing the inner caliper seal. If you find particles or dusting, then wipe the piston down again and then repeat the process until the piston comes out clean, then return to piston into the bore. Then put the dust boot back over and ensure the boot gets pressed in well into the retention channel so it doesn't pop out.

I had a dust boot on one side of the rear pop out at the end of last year's HPDE events. Found it over the winter while I had the car up on the jack stands. The piston was very dirty and mucked up with brake dust and everything else. After a few cleans the piston worked very easily and brakes felt great on the track.

I did ask the shop to torque the upper strut nuts; they said that they did and they were pretty close already. They can be torqued with an open-end torque wrench attachment (which I don't have) while holding the top of the shaft with another wrench. I think I will mark them to check that they are staying put, like SVT suggested.
Yep, sounds similar how I did the torquing of the top nut. I used a crows foot at a 90 degree angle to the toque wrench while holding the top of the shaft. A poor man's witness mark can be done with a Sharpie by marking a line from the top of the nut across the exposed threads of the shaft. If that line becomes disjoint, then you know the nut has moved in relation to the shaft.

Here's hoping you figure this noise out and it is something simple like rear pads being worn. (y)
 

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Discussion Starter · #10 ·
thanks again for these suggestions

. . . Most calipers are reman or off-brand, which you don't know the longevity of. I would not run off-brand calipers if you are doing track events. Stay with the original Motorcraft ones.
I have already replaced them once, with whatever they had at the local Advance Auto, so I assume they are remans. They look like OEM. They have been through a few track days, and they do tend to get pretty hot, so they might be due for replacement. I was thinking of maybe doing the powerstop "upgraded" calipers, link below; which look like OEM painted red and hopefully with good components, higher temp seals would be good. But I don't really want red, my front Brembos are black.


As for big brake kit, don't do it on the rear. Even the '12-'13 Boss 302 have the brake size and caliper you have . . . . If you go to a bigger diameter rotor/caliper setup in the rear, the knock back on the track driving will become more noticeable due to how the axle shifts in and out of the housing on turns, as you mentioned.
I wasn't aware of that side-to-side thing. I already have the upsized rear rotors from later GT500, which made a big difference to the heat in the rear brakes. So I'll stick with the "normal" calipers like you suggest.

The new Torsen you mentioned . . .
I'm hoping the new Torsen cures my spinning problem from last year, which I am trying to blame on my shot LSD diff, hoping it was not simple driver error. For sure the old diff was shot; my inside wheel was spinning like crazy on corners where it only slipped a little in the past.

For possible caliper sticking, you can extend the rear pistons without the pads (care not to over extend so much the piston comes out of the bore), remove the dust boot, clean the dust boot with water and some mild detergent, and then clean the piston surface. . . . The piston was very dirty and mucked up with brake dust and everything else. After a few cleans the piston worked very easily and brakes felt great on the track.
Thanks for that. Yep I will take a good look at them and try cleaning them up, before I buy new ones.

. . . sounds similar how I did the torquing of the top nut. . . . . A poor man's witness mark can be done with a Sharpie . . .
good idea, will do, now that I know they are torqued down correctly (at least I hope the shop did it right; they seem pretty reliable but you never know for sure unless you do it yourself)

Here's hoping you figure this noise out and it is something simple like rear pads being worn. (y)
indeed, thanks again for the helpful tips!
 

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I wasn't aware of that side-to-side thing. I already have the upsized rear rotors from later GT500, which made a big difference to the heat in the rear brakes. So I'll stick with the "normal" calipers like you suggest.
The up-sized rear rotors can result in more pronounced brake knock back while driving on the track due to their increased diameter. There are things you can do to mitigate the issue and ensure you don't get a sunken pedal in a critical braking zone. The Torsen was one of those things, so that helps. One of the easiest things to overcome it is to tap the brake lightly before the actual braking zone on the track. Then release the brake pedal and then do the actual braking. This takes up the slack and ensures the piston and pad on the rear are situated close to the rotor for minimal piston extension before initial grab or "bite".

I'm hoping the new Torsen cures my spinning problem from last year, which I am trying to blame on my shot LSD diff, hoping it was not simple driver error. For sure the old diff was shot; my inside wheel was spinning like crazy on corners where it only slipped a little in the past.
If it is like what I found, my first track day a month ago was night and day different after I changed out the LSD clutch discs in my differential. During the previous year, I was finding I was spinning like crazy on the lightest throttle input at apex and wet track conditions were a nightmare. I couldn't get throttle steer to happen at early corner entry, and I thought I had lost my knack for track driving. 😄

As I found out last winter, I basically had an open differential before I changed the friction discs; I could easily rotate the rear wheel by hand while one side was on the ground! After the install of the new discs, I couldn't budge them and the torque wrench clicked at the lug nut torque without braking loose, so it is >90 ft-lbs of bias without being broken in. Throttle steer was night and day different and traction out of apex was straight and true. No more loosy goosey. SO much fun and safer!

The Torsen will make a world of difference for your driving, I am pretty sure. I was inclined to install a Tosen or actually a Truetrac, but decided I would do the simpler option and change out the LSD friction discs and new S spring. I figured I would get another season or two out of these new ones and see where I go from there.
 
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Discussion Starter · #12 ·
Well, turns out, yes indeed, the rear pads were very low; not gone but low enough that the spring clips were rubbing on the rotor, and that must have been the source of the noise. The rotors look fine.

Passenger side caliper looks OK, slides OK, generally seems to be OK; but the driver side has a torn rubber boot (on the piston). So now I am looking around for parts; I can get a "caliper repair kit" that hopefully includes the correct boot and seals; not sure how to change them but I can figure it out. I can get new caliper from Tasca Parts for $128 but probably not in stock for this weekend. I kinda like the Power Stop calipers, but I wish they were black, seems goofy to have black on the front and red on the rear. All the other auto parts stores around here only have the cheap remanufactured calipers; I guess they would be fine but I'd like something "better" while I am at it.

Decisions, decisions . . .
 
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Well, turns out, yes indeed, the rear pads were very low; not gone but low enough that the spring clips were rubbing on the rotor, and that must have been the source of the noise. The rotors look fine.

I kinda like the Power Stop calipers, but I wish they were black
Couldn't you paint the caliper before installing it? A buddy of mine painted his Audi calipers and they came out fantastic
 
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Discussion Starter · #14 ·
Couldn't you paint the caliper before installing it? A buddy of mine painted his Audi calipers and they came out fantastic
Yeah that could be a good option. I already have the black caliper paint. They come red powder coated and I assume the spray paint would stick OK to that, if I rough it up a little first.
 

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PowerStop is a good choice. As the rear brakes only do about 30% of the braking, doesn't pay to spend big $$ on rear brake calipers when the OEM's are sufficient. Think I mentioned this once before, years ago as we were upgrading our car, I spoke to a few mustang race teams to see what they were running for brakes and was surprised when I was told they run Ford OEM rear brake calipers. Naturally they run 4 & 6 piston up front, but most do....... Be sure the caliper paint is good for at least 1500* of heat. Little more than you'll hit, but always good to have more.
 
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Discussion Starter · #16 ·
I went ahead and ordered the PowerStop calipers from AM. They are supposed to be here on Saturday. I do wonder if the powder coat is good for 1500*F, I doubt it, but will probably paint over it with black and cross my fingers that it comes out OK, and holds up under high temps.
 
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JBert, I'm happy you solved your problem about the noise when turning left. I was at the point to offer you my limited logic, and recommend you avoid left hand turns and just drive straight or only make right hand turns to your destination like a UPS driver.

Let me know if I can be of further assistance. :D
 

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Discussion Starter · #18 ·
or always drive the wrong way around a NASCAR oval? LOL . . . if I ever do actually get back to the road track this year, it will be interesting to see how the powder coat holds up.

I think I might try the red calipers on the back (with the black brembos on the front) and see how much I hate it, before I bother painting them.
 

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or always drive the wrong way around a NASCAR oval? LOL . . . if I ever do actually get back to the road track this year, it will be interesting to see how the powder coat holds up.

I think I might try the red calipers on the back (with the black brembos on the front) and see how much I hate it, before I bother painting them.
J, just curious but what kind of speeds do you get up to out there? Sounds like a blast.
 

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Discussion Starter · #20 ·
Yes indeed it is a blast . . . I go to Thompson Speedway road course (Thompson, Connecticut) most often; main straight is around 115 MPH . . . car is solid as a rock at that speed and still accelerating strong, but turn #1 comes up quick. Getting my car out on a track was a "bucket list" item for me; but then I discovered, track days are like Lays potato chips; nobody can have just one. If you want to try it, check out tracknightinamerica.com ; probably the easiest way to get on track, assuming they run events at a track near you. But be forewarned, it is highly addictive, and gets expensive like any good addiction.

I ordered the calipers from American Muscle, mainly for convenience, plus the web site said I would have them on Saturday . . . when I didn't receive a shipping update yesterday, I wondered what was up, called American Muscle . . . they shipped this morning, and will be here on Sunday, supposedly. I do understand that reality, not the end of the world, but I'm disappointed that their web site lied, and I told them so on the phone.

~ John B.
 
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