Hi guys,
I have a harmonic noise in my rear diff area that the dealer can't find. We have replaced the diff twice, and the driveshaft once. Gonna kind of ramble here, don't know what's relevant, but y'all are pretty smart on here.
I first noticed it at 3500 miles immediately (driving off the lot) after having downpipes and a diff brace installed. At this point, the car only had Eibach lowering springs, Fenfab charge pipe and turbosmart blowoff valve. The springs produced no issues for 2+ weeks before having the downpipes put in. I've been troubleshooting this the last 15k miles as a brace issue, but recently switched from AWR to ID Speed (improved bushing design) and found that the sound is present with the new brace AND with the brace removed entirely. The brace definitely makes the sound louder, but is not the cause. I drive a '23 ST now, but did not experience these issues on my '22 with very similar mods.
I've had a couple shops look at it to no avail. Ford just keeps replacing the diff as metal is present. The first driveshaft would not come out because the splines were twisted, and they had to destroy it to remove it. Got to thinking about the shop who did my downpipes, and remembered I sent them an install guide that suggests loosening the front subframe and possibly the transmission mount. I got under the car and checked the front subframe bolts, they all seem tight but the subframe is shifted to one side by a tiny amount, probably under 1/8-inch. The transmission seems OK.
The other thing that got me to check the subframe alignment is that I am getting what feels like driveline binding/mild vibration in the 30-40 mph range after installing a JXB driveshaft carrier. I'm totally OK with some vibration for the upgrade if this is expected, just wanted to include it as a data point.
Not sure where to go from here, open to suggestions. I'm having some pretty smart dudes look at it here in a few weeks, anything I should ask them to check? I'm very suspicious of the front subframe/diff area but do not have any drivability or alignment problems -- Just an annoying noise.
Thanks for reading
I have a harmonic noise in my rear diff area that the dealer can't find. We have replaced the diff twice, and the driveshaft once. Gonna kind of ramble here, don't know what's relevant, but y'all are pretty smart on here.
- It sounds very similar to this: Hellcat rear end whine. It is a terrible noise with a pitch that the radio and a thermal 3" exhaust can't cover. Multiple passengers are reporting it's coming from the rear diff area.
- Barely noticeable hum 30-40 mph. Loud at 58-63
- Noise disappeared entirely in the winter. Came back in the spring.
- Transmission gear does not affect noise.
- Turning does not affect noise.
- Load does not affect noise.
- Louder on decel, but present on light throttle in the listed speed ranges.
- Sound seems to go away if I put the vehicle in Neutral and coast down through the 63-55.
- This was not present when the vehicle was brand new.
I first noticed it at 3500 miles immediately (driving off the lot) after having downpipes and a diff brace installed. At this point, the car only had Eibach lowering springs, Fenfab charge pipe and turbosmart blowoff valve. The springs produced no issues for 2+ weeks before having the downpipes put in. I've been troubleshooting this the last 15k miles as a brace issue, but recently switched from AWR to ID Speed (improved bushing design) and found that the sound is present with the new brace AND with the brace removed entirely. The brace definitely makes the sound louder, but is not the cause. I drive a '23 ST now, but did not experience these issues on my '22 with very similar mods.
I've had a couple shops look at it to no avail. Ford just keeps replacing the diff as metal is present. The first driveshaft would not come out because the splines were twisted, and they had to destroy it to remove it. Got to thinking about the shop who did my downpipes, and remembered I sent them an install guide that suggests loosening the front subframe and possibly the transmission mount. I got under the car and checked the front subframe bolts, they all seem tight but the subframe is shifted to one side by a tiny amount, probably under 1/8-inch. The transmission seems OK.
The other thing that got me to check the subframe alignment is that I am getting what feels like driveline binding/mild vibration in the 30-40 mph range after installing a JXB driveshaft carrier. I'm totally OK with some vibration for the upgrade if this is expected, just wanted to include it as a data point.
Not sure where to go from here, open to suggestions. I'm having some pretty smart dudes look at it here in a few weeks, anything I should ask them to check? I'm very suspicious of the front subframe/diff area but do not have any drivability or alignment problems -- Just an annoying noise.
Thanks for reading
