So I finally got my dream XJ but my partner hates how loud the car gets past 60mpg. She's very sound sensitive unfortunately (migraines are very debilitating) and I need this car to be right to justify keeping it around. I was wondering how folks have been quieting their cab and how effective they've been.

I'll be doing the basic headline upholstering this weekend and just ordered 80mil kilmat to do the roof at the same time. But the videos I've seen aren't too convincing and most of the threads I find about it seem to say more that the sound does get quieter, but others point to placebo because the sound simply changes, as opposed to significantly silences.

I also have a stock muffler that has some rust on the bottom. I don't see any holes, so I don't think there's too much plugging to be done. I was thinking about getting a flowmaster as well, but again the videos I've watched don't seem too convincing. Interested to hear what folks have experienced and recommend.

Also here's the pic of the baby

 

If she is sensitive to noise, stick with the stock muffler. When you take the headliner down, get some stick on sound deadening material from someplace like Summit Racing and install it in the roof under the headliner. Pull up the carpet, put some under there too. Take the panels off the doors and put some inside the doors too. Panels in the back also. Anyplace you can remove panels, put sound deadener there. Sometimes, if you can, layer it. Make sure the carpet has sound padding under it too.

 

I have found the majority of the noise comes from the floor closest to the engine. Some good street tires will help keep noise down too. And as usual, check for noisy bearings and exhaust leaks, which can make a significant improvement in cabin noise.

Bottom line, it's not a quiet vehicle by today's standards. I also doubt that it can be brought anywhere close to that.

 

The killmat will dampen some vibration but it has it's limits considering it's pretty thin. Avoid the asphalt based stuff, btw, the nauseating tarmac smell sticks around a lot time. Dynamat makes some stuff that's a sandwich style acoustic mat that works far better than the cheesy stick on vinyl tile junk. https://www.crutchfield.com/S-Rryc47...ound-pt-4.html Dynamat is expensive and there are comparable alternatives out there, too.

Pull the carpet up and treat the floor, particularly up and over the transmission hump and front of the foot wells. My cabin noise is a lot louder and the transmission much more noticeable without the carpet. You need to look under the carpet anyway to assess and deal with any rust before you have a Fred Flintstones replica. As a last resort

 

Thanks for the responses. So I'm already planning on doing the roof, doors, floors, and as much of the interior firewall as possible. There's no rust on the unibody (thank god), but It sounds like it won't make any considerable changes. Am I reading that right?

Also thinking about getting the Walker quiet muffler.

 

Lawsoncl gave you some good advice.
The only thing I could add to it is also consider getting your XJ asphalt undercoated including inside the frame rails. It's famous for rust prevention but it's a heck of a sound and vibration deadener.
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Don't forget underneath the rear seat and the cargo area. Get a good quality thick carpet to throw over the cargo floor. That whole area acts like a drum transmitting sound from the rear suspension.

 

Cab noise comes from many places. One I don't see mentioned above is wind noise. Check your door and window seals, as well as your jamb adjustments. Your doors should have plastic sheets under the trim panels to keep wind and water out.

The XJ is not the most "aero" design (more like barn door) so there are limits but you can drastically reduce noise and draft.