I installed the same cat back system several months ago with secondary cats deleted. The drone is irritating. I have been pondering that 17748 muffler replacement for awhile.After 16 years of stalwart service, my stock exhaust reached the point of rust induced death. I've been patching it up over the years, but could no longer stand the exhaust leaks. However, I'm not a fan of loud exhausts, and will not tolerate drone. Ideally, I would have replaced it with a stock replacement, but those are just not available and they are quite expensive when you start piecing together a cat back from OEM parts. So after a bit of research, I found the Dynomax Cat Back system. I found it for less than $300, so it is pretty cheap for a fully stainless cat back. I didn't want a fabricobbled exhaust from a shop, even though that is cheaper. Lots of people do a 2 into 1 muffler and have everything else bent up. But for the price, and not having to see bubblegum welds and kinked bends under my truck, I pulled the trigger. The whole thing is well constructed with good quality welds and a polished exhaust tip.
However, I'm very aware of the complaints about loudness and drone from Dynomax's kit. But there is an easy solution. In addition to the cat back kit, I also ordered Dynomax's Super Turbo muffler to replace the Dynomax Ultraflow muffler that comes with the kit. The Ultraflow is a welded stainless steel constructed strait through design. The Super Turbo is of galvanized crimped construction with an 's' shaped exhaust path through the muffler.
See: Mufflers for details.
Dynomax makes a 2-1/2" offset inlet with a 2-1/2" center outlet muffler of the same length in both lines. So it was as easy as ordering both the Catback Kit and the extra Super Turbo muffler. You end up with an extra muffler, but its still under $400 for all of it. The kit comes with U clamps and gaskets, but I hate U clamps on exhausts, so I ordered 3 x 2-1/2 Walker Mega-Clamps to replace the U clamps. These look more professional, in my opinion, and make removing the exhaust, for say replacing a clutch, much easier down the road.
The parts I used are:
Dynomax Cat Back Stainless Kit (Part Number 19443)
Dynomax Super Turbo Muffler (Part Number 17748)
3 x Walker Exhaust 2-1/2" Lap Joint Mega-Clamp (Part Number 33226)
This is very easy to install. The hardest part is removing the old exhaust. Be prepared to break many of the studs between the secondary cats and the downstream exhaust pipes. There are two studs per side, threaded into the secondary cats. If you break one, don't panic. Drill out what's left of the stud and replace it with a nut and bolt. You may be able to drill out broken studs on the truck, or if you are unlucky, you may have to drop the secondary cats which will probably result in more broken studs. Just soak all the studs in penetraing oil well before hand. If you don't break any studs, you can have this done in a couple hours. Or if you have to drill them all out, this could take all day. Budget time accordingly. Other than that, its pretty simple. You may also find cutting the stock exhaust apart easier than trying to unbolt the parts from each other. A reciprocating saw with a fresh metal cutting blade may prove useful.
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Noise Level: Even with the replacement muffler, this is noticeably louder than stock. On a scale of 1 to 10, with 1 being the stock exhaust, and 10 being no muffler at all, this is about a 3 in terms of sound level. At idle, its nearly stock quiet, which is almost silent inside the truck. Under load, starting at about 2k rpm, you start to hear it. It's not annoying, but its noticeable. To me it sounds about like a stock 370z when its under load. Not bad, but its still a growly little VQ. At speed or under load, there is no drone.
Lots of folks bemoan the restrictive stock crimp in the two exhaust pipes as they join to enter the stock muffler. This kit does away with that using a simple 2 into 1 welded joint before the muffler. I have been sceptical that removing the stock crimp joint would make a performance difference, but in my case, the cat back made a measurable improvement. I don't know if its the new joint or the less restrictive muffler, but in testing roll-on 0 to 60 times, the truck is 0.4 seconds quicker with the new exhaust in back to back runs. So color me impressed. (2006 Xterra Off-Road 6MT OBD-2 logged times)
If you are looking for a nearly stock sounding exhaust, and don't mind giving up a fully stainless cat back to get that sound level, this is about as easy and cheap as it gets for a high quality bolt on exhaust. And it may just make your truck just a bit faster.
After what you report, I'm going to pull the trigger and buy it