2015 wrangler JK. 88k miles, 35” tires, recently upgraded to 4.56 gears from stock 3.21. Noise was there prior to gears though.

I have this humming/groaning noise coming from the rear of the Jeep. Almost like exhaust noise but it’s not all the time. If i take my foot off the gas it stops completely. A little bit of vibration in floor accompanies it but hardly. Only audible when in gear, nothing when parked and engine is revved up. Shop who did my new gears inspected them today and changed gear oil and all is good in that department. They drove it and had a hard time hearing it because it’s only at certain points. They mentioned the parking brake assembly or spring or something seems off and that could make a noise but i don’t think that’s what I’m referring to, might be something else they heard. Noise seems like it’s more noticeable at 20-25 mph or other speeds right after shifting to a new gear, and after Jeep is warmed up. I’m wondering if the transmission is struggling or it’s a driveshaft or something. Or maybe exhaust leak? There is a dual exhaust.
Debating if it’s worth having dealer look at it or not, it’s under power train warranty but I know it’s gonna be hard for them to hear it & I’ll probably get the $159 diagnostic fee for not hearing it


link to YouTube video - noise in video starts about 3 seconds in through 12 seconds. And then again from 20 seconds to end.

 

Video isn't there. Usually easiest to upload video to YouTube, then just past the link here. It will embed the video.

 

Thanks! sorry about that. I added it. & Here it is here- noise in video starts about 3 seconds in and ends at 12 seconds. Then again at about 20 seconds through the end.

 

Man, that is really hard to hear, but admittedly I'm on a Chromebook that doesn't have the best audio. I listened on my phone as well but it wasn't any more clear. I could barely hear what I believe I was listening for, but to me it sounded more like exhaust. One thing to keep in mind is that after regearing, the RPM range at a current speed is going to be different than what it was before, and that will translate to exhaust sound with that aftermarket muffler. I'd also say that exhaust isn't going to sound the same revving it in the driveway at 3k rpm as it will driving 70mph down the road at 3k rpm in gear, under load for a period of time. Since the sound was there before the regear, and the gears aren't wearing abnormally and all bearings are new, seems like that isn't related. Maybe someone else might hear something and it rings a bell.

 

very insightful thank you! It is hard to hear in the video. If it was exhaust would it be audible any time I’m accelerating, or no? This noise is only at certain points so I wasn’t sure if it could be exhaust.
Trying to think of how else to describe it. When I took the doors off, it’s much much louder obviously and it’s a very deep sounding humming but the frequency of it actually irritates your ears. It almost feels like when you drive in a car on a highway with only the rear windows down. Not the fluttering obviously, but it irritates your ears like that. Idk! I guess I’m gonna bring it to dealer while it’s still under warranty in case it is transmission or something and see what they think

 

I don't suppose you have an old phone or something you could tape up under the jeep to record it closer to it's source huh?

 

Have you noticed a specific rpm range on the noise
If you can get it to make the noise at a set rpm, you might be able to make the noise sitting still without being on the road and might can narrow it down better

 

I ended up dropping it at the dealer last night for appointment today. They just called and said everything looks good and feels tight. They’re saying there is an aftermarket exhaust that is a little louder than stock and that’s all they’re hearing. He said the stock exhaust has a double wall and this one seems thinner so that’s most likely what I hear.

 

I have an aftermarket muffler on mine. It doesn't have the same drone as a lot of those catbacks out there, but I hear it. When I remove my foot from the gas pedal, and groan, growl, droan....however you want to reference it...drops off very quickly. Like a second or two. This is the same whether cruising on the highway at 3k RPM or driving 30mph down a residential road in a lower gear. You might just play around and and see if you can replicate it at will at various speeds. I suspect it's just that your RPMs are now in a different range after the rear, which is translating to a different exhaust tone in that range vs what you were used to before. I do think though that if you have an old phone (or a gopro) that you can stick under the jeep and drive around, you're going to get a much louder and clear sound which could help identify it. Pinpointing noises is typically a little trial and error.

 

Thank you so much. I do hear it at lower speeds too they are just different tones at different RPMs, but yeah I think you are right that after the regear it sounds different at different points to me. I am definitely going to borrow a gopro from a friend and hook it up underneath while I drive. Should get to it early next week. I will post that video on this thread and if you get to it let me know what you think! I appreciate all of your advice.