I have a 05 G35x and after only 60K in Chicago the flanges connecting the muffler to the mid-pipe were shot and eventually separated. They completely rusted away, but the pipes were in ok shape. The pipes and muffler are well supported. Since the flanges are installed before the pipes are assembled they are considered one part/non-serviceable, old style/old problem. Dealer wanted $850 for 2 complete exhaust sections installed. I could have gotten cheaper replacements for a few hundred and done it myself. Or this could have been the excuse for a Stillen cat back system for a grand. But money is tight so I wanted to cheap the fix in a secure way.
I was first going to cut off the expanded edges and use a 2 1/2" butt/slip connector to attach them. But then I found these Walker split flange kits. Used two 2 1/2" sets #36130. Worked great. You can get them from NAPA ($56 total) or Summit Racing ($46 total). You need to supply the 2 bolts that connect the sets (2 1/2"-3" bolts, nuts, washers,). Even had some in my junk box. The metal compression gasket was is good shape so it seals fine. Be careful when removing any remaining flange not to ruin it. If yours is damaged you could get a generic 2 1/2" double beveled gasket to work. The rest of the exhaust will crap out before the repair does.
Shops never tell you about the easy repair kits. I assume many other have the same problem on their cars.

 

Thanks for posting this! I was able to follow your post and fixed my '05 G35x. The hardest part of this repair for me was to saw off the rusted flanges. Eventually, I used a hacksaw and an oscillating tool to get the job done.

 

Thats cool.
But wheres your grounding wire??0_o

 

Good post. My exhaust has been louder than usual lately. Took a look a d my flange is rusting apart. Was going to get a slip on tube, but this looks like it might be a better repair.

Is there a donut between the two flanges? Or is it ball and socket type?

 

I'm getting ready to do my '03 coupe. Looks just like the first pics. I purchased an OEM gasket from Infiniti ($11). It's just a ring/doughnut. I'd go to infiniti and purchase this part. They guy pulled out two items, different part numbers, but looked exactly the same. One for the coupe, the other for the sedan. Who knows why? I've also sketch a little drawing of the pipes from what I can see. I will try to take more pics durring the install.

Seams like an easy fix.

Edit: After attempting to do this fix, we ran into a lot of problems. The half of the flange that was left was so rusted on, it took 1/2 hr with the pnumatic chisle to get it off. Probably my fault because I let this go so long ( 2-3 years). Then the larger end would not fit into the smaller end.
In the end, my friend was able to make me a new beviled gasket to fit between the ends. So my sugesion is if you don't have the experience to come up with a fix like this, then take it to a muffler shop and have them fix it.

 

I got a local shop to just weld them back together. COst me $100 though.

 

I was working on 2006 G35x 111k driven in New England. Same issue as OP, flanges on both the muffler and B-pipe completely rotted.
I bought the split flanges planning to implement the same fix as OP, but when I took things apart I realized that both muffler pipe and b-pipe are the same diameter, 2.5 inch.
There is no way that one pipe could slide into another pipe. Perhaps I misunderstood what the OP did or perhaps his exhaust is different. Anyway, I had plan B for this repair, which is even cheaper than the OP repair.
I bought a pipe coupler from Advance Auto Parts with 2.5 inner diameter and 2 U bolt clamps, for grant total of about $10. In order for coupler to work, you have to grind down the remnants of the flange welds. I disconnected the muffler and ground down the metal on my
bench grinder. For the B-pipe, I disconnected the two rear hangers, letting the pipe to come down. Then ground it with my Rotozip and metal cutting disk. Will definitely invest into a small grinder. Once both pipes were ground flat, the coupler just slides on and 2 U bolts clamps hold everything together nicely.
Thank you to OP for an idea, would love to hear little elaboration on original repair.
Here are few pics from my repair.

 

they have these parts on Amazon for only $20.27 a piece:

 

I just took mine to an exhaust shop and had them weld it.

$40 and literally 10 mins later, i had a nice quiet car again and regained some low-end torque.

 

Guys so the exhaust flange at the rear of my 05 fx35 rotted off. I used a flange kit with a 2.5 inch diameter to fix it. With the flange all the way closed it only stops at the flare on the flange not on the pip at the muffler. My question is what is the correct size of the stock exhaust? I also did an external measurement and coming up with 2.4 on the external using a string at 7.5 inches and dividing by 3.14.

I am a little confused and considering using a couple and clamps instead to do the repair but I need to know what size. Does anyone know the exact size ?

 

I don't really know what an '05 FX exhaust setup looks like, so can't really comment.

I did end up buying the flanges and exhaust gasket the OP suggested, but in the end it was easier to have a shop weld it. It's been 2 years now and no prob with the repair.

 

Thanks for the response. I ended up using the original idea with a gasket but the gasket I used was like this -

https://www.google.ca/imgres?imgurl=...G8rs-AGdtrugCA

I am pretty sure these exhausts are 2.25 and not 2.5 like the g35's.

Thanks again. Wife said it is quieter and I am good with that .

 

Great DIY OP! Saved me a few $$$ and some time. I have 2005 G35X with 140k miles on it and on my trip to NY I noticed that my car became damn loud and irritating, I also noticed a metal-to-metal sound on bumps, checked the muffler and it was looking weird, appeared my muffler connection to mid-pipe was shot, 20k miles ago dealer noticed the leak and suggested a 1300$ fix (for 1300$ a fix I would do this all day long), I checked at a few shops if they could weld it but they also told me they wouldn't do this so i had to use google and found this thread. Had to go to two different advance autoparts and to a homedepot to collect the set (including OEM gasket from Altima or whatever it's called but fits 100%) but still took me around 40minutes to get as everything was in stock nearby (so far for living in US, you have in stock something for your 10 year old car you didn't know even exists), it was pain to get rid of the rusted flanges and I recommend a special tool to deal with this but I still managed to disassemble the rusted flange with a hacksaw and a decent pliers but I would recommend smth. automatic which would help you do the job, although hacksaw worked surprisingly well and I didn't expect it would do the job, it was pita but only a small one. Doesn't look as good as OP one yet it's pretty solid and I imagine it will not bother me anymore and probably won't bother inspection guys. Cost me 50$.

Except of that my G is still running strong.

 

Hey Guys just an update. So my flange is leaking at the gasket and I have decided to head back in .

I measured the external diameter on both sides of the flange and we are looking at 6cm. So going to use a 2.5 inch internal diameter coupler with cement and clamps. And well a grinder to take the good side of the flange off.

-B

 

The Walker split flange kits --- 2 1/2" sets #36130 -- are still available. Worked great. CarQuest also had a metallic gasket with a sleeve that slips into the pipe perfectly. JL