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Discussion Starter · #1 · (Edited)
Ok, here's a write up on my free mods. The airbox mod and the rear cat mod.

Airbox mod

Tools needed: Regular curved jaw vice grips, 10mm 3/8 drive socket/ratchet, 6" long extension, flathead screwdriver or something along the likes to etch a line.

First, unplug the MAF connector and position out of the way. Next, loosen the hose clamp around the throttle body. Take off the hoses to the breather box on the intake hose. Next, unclasp the airbox and set the whole assembly aside. Pull your air filter out and you will see where the tube comes into the factory box down towards the bottom. It is very close to the bottom of the airbox as you will see. There are 2 bolts that secure the airbox that you need to worry about. One is right behind the airbox off to the drivers side fender. The other is inside the airbox assembly. Loosen those and make a mark where the tube comes into the airbox assembly. Gently pry the airbox assembly out of the truck. You will need to pry the cold air tube from the side of the airbox assembly to make it shorter. After you get the cold air tube out, use the vise grips to take a bite and give it a sharp pull and a piece will break off fairly cleanly. It doesn't require much effort as the plastic is pretty brittle. As you make your breaks, you will see the pattern of how the plastic breaks. Just keep at it going around the tube until you get to your mark. You can use a file, sand paper or whatever else you want to smooth it down but I just put it back in there. The important thing is to make sure there is no pieces left loose. Put the shortened tube back into the airbox and you will see that it should sit flush inside the airbox where it used to protrude from. Reassemble everything the reverse of how you took it apart.

Secondary cats

Tools needed: Large adjustable wrench, 14mm socket, 3/8 drive ratchet, 14mm combination wrench, 3 or 5lb hammer, WD40, (never seize is optional) patience..........


First, spray the exhaust hangers with WD40. Then spray the cat flange nuts with the WD40. Let it sit for about 15-20min. After you let it sit, you will need to get under the truck and go loosen the O2 sensors. Use the large adj. wrench and get it really tight around the nut part. After you do, take the hammer and give the bottom of the wrench a couple of good sharp whacks and it should loosen right up. Unscrew them all the way out and set them aside to where you won't hit the tips. Next you want to use the same method with the 14mm combo wrench on the front and rear cat flange nuts to loosen them with the hammer. After they are loosened, use the ratchet to speed in taking them off. Set them aside somewhere where you won't lose them. Now comes the fun part........(remember patience). You need to push or scoot the exhaust system rearward just enough to where it clears the studs to which it was attached. 1" will suffice. Remove the gaskets noting the direction they were put on so you can put them back the same way. Now remove the front flange nuts and set them aside. Wiggle the B-pipe assembly out from under the truck and set aside. Do NOT mix them up!! Keep them separated on either side. Take your freshly removed B-pipe assembly and go outside. You will be using the same hammer as before and a large flathead screwdriver or prybar of sorts. Drive the tool down into the middle from the rear and just have at it. The cat material is surrounded by some kind of heat resistant fibrous wrap. Knock out all the chunks/pieces and make sure you have everything off of the walls inside. If anything lingers, just take your tool and scrape the insides until it's clear. After you get everything out, set it back down under the truck from where it came from. Reattach them to their respective primary cats. Slip on your metal gaskets, start the front nuts and wrestle the exhaust system back onto the rear studs. After you get it on at least half the studs, you can start the back nuts. Tighten the front nuts first, then the back ones. It doesn't have to be superman tight but pretty snug would help. I recommend using never seize on the O2 sensor threads before you put them back in. To put them in, twist them counter clockwise until you have enough wire twisted to get them back in with it not twisted. Now you gotta clean up the mess you made from the cat material.......lol. Fire it up and check for any leaks from improperly tightened nuts.
 
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Sprayed the nuts and o2 censor with wd40, waited 15 minutes, grabbed my tools and went to town....

5 minutes later my first bolt was stripped and I am back in the house watching TV. F&(#$) guess I needed someone elses help. anyone want to take a road trip to cheyenne and show me that I'm a retard?
 

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Hey Fly Boy, I love that video. lol
 

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Sprayed the nuts and o2 censor with wd40, waited 15 minutes, grabbed my tools and went to town....

5 minutes later my first bolt was stripped and I am back in the house watching TV. F&(#$) guess I needed someone elses help. anyone want to take a road trip to cheyenne and show me that I'm a retard?
If its stripped then just cut it off flush, drill it out and go get you a 1/2"x2 bolt and wiz nuts. I had to do the same thing on two of mine. Actually works better than those crappy studs nissan uses. Wish I would have done em all like that. You are talking about the studs on the actual flange right???
 

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The airbox mod took me all of 15 min. I got the top out of the way, removed filter, took sawzall to the offending tube, trimmed top of tube off, sucked chips out with a shopvac, reassembled, done!
 

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If its stripped then just cut it off flush, drill it out and go get you a 1/2"x2 bolt and wiz nuts. I had to do the same thing on two of mine. Actually works better than those crappy studs nissan uses. Wish I would have done em all like that. You are talking about the studs on the actual flange right???

I was going to take a torch to it, but now I think I might be a deet da dee. If your starting that the nut, its standard righty tighty, lefty loosey right? or is it going to be reversed looked at the nut?
 

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ok, then those b!tches are ON there!
 

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go get some PB blaster and let it soak in. that stuff works wonders! also get an O2 sensor socket, 5-10 bucks and it wont strip the sensor or crush the wires. Remember guys the right tool for the job will save you a trip to the dealer.
 

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Ok so I have done the Air Box mod and have attempted the Rear Cat Knock Out mod and this is where I am...

Air Box took me 10 minutes. Easiest thing I ever did, mod wise!

Rear Cat Knock out. Nissan bolt are crap. Headed to home depot or sears to get some stripped bolt removal sockets to get those crappy bolts off of there and replace them with thwe 2 1/2 x 2 bolts and the wiz nut. Will let you know how it goes.
 

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I suppose im luckey I work at a shop where I have my own lift that I can do whatever I want on after hours. :) not to mention over 15k worth of snap-on tools I have.
 

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photos pls... I need to do the secondary cats DIY mod... This is only for the 4x4 right?
 

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heres some pics I got from when I gutted my cats and my air box mod.
 

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Can anyone answer my question please? I'm a sportsbike person, new to modding trucks.

Thanks
These mods make your truck breath better. Which make it run better and faster. These two mods arent going to make it alot faster but it will help out some. I did the airbox mod and ran with it for 4 months and then got the S&B CAI.( Cold Air Intake) I also did the rear cat delete and I feel it helped my top end a little. Mabey .1 in the 1/4 Both mods together might give you .2 in the 1/4 mile. I do know that the S&B gave me .2 in the 1/4 mile and made me 2 to 3 mph faster in the 1/4 also.
 

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Discussion Starter · #19 ·
These mods make your truck breath better. Which make it run better and faster. These two mods arent going to make it alot faster but it will help out some. I did the airbox mod and ran with it for 4 months and then got the S&B CAI.( Cold Air Intake) I also did the rear cat delete and I feel it helped my top end a little. Mabey .1 in the 1/4 Both mods together might give you .2 in the 1/4 mile. I do know that the S&B gave me .2 in the 1/4 mile and made me 2 to 3 mph faster in the 1/4 also.
This man speaks the truth!! It's not a whole lot of gain performance wise, but it is free and those are the best mods, free ones......lol.
 

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This man speaks the truth!! It's not a whole lot of gain performance wise, but it is free and those are the best mods, free ones......lol.
I second that.
 
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