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BMR lockout kit causing clunk when not in gear??

vtchopperdude

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Fellas, I've owned my Mustang for about 6 months now. Since the weather has been nice, I've been driving it more often. I purchased it will all the suspension mods already done (listed in my sig). I have noticed a clunk/rattle from the rear when turning at low speeds and not in gear. If I am in gear, then no clunk or rattle. For example, when I turn into my driveway, I notice it. Or pulling into a parking spot, I notice it. It seems to only do it when going parking lot speeds, but it may be doing it at all speeds, but I just can't hear it. Again, only makes noise from the rear when NOT in gear. The clutch can be in or out, but as long as it's not in gear, it clunks.

That being said, I reached back to the previous owner. He was confident that the BMR bushing lockout kit was causing this. He mentioned that it made this sound when he had the bushing kit installed. It bothered him, so he had the stock bushings put back in, and the sound went away. He later had the BMR bushings put back in for track use.

His rationale (his mechanic's rationale) was that the bushing kit firms up the IRS, and when not in gear, the sound of the gears in the differential not under load (not in gear) while in a turn is magnified. Does this seem reasonable??? Or is something not torqued to spec??

Of note, the car drives great! It handles great! And will spins the tires without issue. Am I being overly worrisome?

I uploaded some pics of the rear suspension components. Nothing looks out of place to me...
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KellTrac

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Performance Pack car?

Probably your diff. Make sure all the bolts under your car are torqued properly and enjoy it.
 

moffetts

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If it's only happening in gear, then the diff bushing inserts (or are they the bushing replacements? I can't tell) are probably the culprit. They convey all sorts of strange noises straight into the cabin. If they are the full blown bushing replacements (BK049) then you are screwed because short of replacing the entire subframe, you can't go back to the stock bushings.
 
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vtchopperdude

vtchopperdude

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Performance Pack car? Probably your diff. Make sure all the bolts under your car are torqued properly and enjoy it.
Yes, it's a PP. I didn't check torque specs when under it yesterday. Just tried to see if anything obvious was out of place, or it was an exhaust hanger bumping on something. Like I said, it drives great! And it loves to eat rubber! It is just more "clunky" thank previous Mustangs I've owned. It seems the S550 is notorious for random clunks, rattles, and squeaks. I still enjoy the hell out of it though!!!

If it's only happening in gear, then the diff bushing inserts (or are they the bushing replacements? I can't tell) are probably the culprit. They convey all sorts of strange noises straight into the cabin. If they are the full blown bushing replacements (BK049) then you are screwed because short of replacing the entire subframe, you can't go back to the stock bushings.
To clarify, the clunk ONLY happens when in a turn and OUT OF GEAR. As far as the bushings, they must be inserts. Like I mentioned in the original post, the previous owner noticed the same clunk, so removed them, and the noise went away. But, wanting to use it on the track, he put them back in, and the noise came back. I didn't specifically check the torque on them, but if they firm everything up, then maybe that is just magnifying the sounds coming from the diff when not in gear and things are not under load in the rear end. Maybe?? I don't know. That's why I'm asking to see what others have experienced when running the BMR lockout kit. Thanks.
 

Dr. Norts

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Just curious why are you out of gear when turning?

I'm trying to think of a situation that warrants this.
 

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vtchopperdude

vtchopperdude

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Just curious why are you out of gear when turning?

I'm trying to think of a situation that warrants this.
As I approach my driveway, I slow down, push the clutch in, and turn in. I get the rattle/clunk in this scenario.

And similarly in a parking lot, turning into a parking spot. Same rattle/clunk.
 

thebaldlatino5.0

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it's the torsen diff. It'll make noise when you stiffen things up and when it's not under load, it'll make small noises.
 
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vtchopperdude

vtchopperdude

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That's the Torsen diff. You are hearing it because of the IRS modifications.
it's the torsen diff. It'll make noise when you stiffen things up and when it's not under load, it'll make small noises.
Copy all! Thanks fellas! That's the knowledge and experience that I was looking for! I'll press on and not worry about it anymore!
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