4.0 air intake tube on 2.5?

J

Jainee

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Oct 19, 2019
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I have CEL and I noticed my air intake box is melted.

I read a lot about cold air intake and thought if I could just use stock air box with different tube. To avoid open filter but new tube kit.

I could buy 2.5 cold air intake kit from airaid or aem or rough country and try to link it into stock filter box. That’s expensive trial.

I wanted to ask if anyone did use 4.0 intake hose and tube for 2.5? Do you see any issues in fitment around throttle body or stock filter box?

if yes, is there any place I could buy 4.0 (stock or aftermarket) tube and/or hose for my 1998 TJ 2.5?

Any advice.

42053D51-E28F-43E1-B064-D5857AD07B1D.jpeg
 
Thank you.

My question is if I can use 4.0 air intake assembly on 2.5? The fitting, length, location or concerns?

I’m not changing the throttle body or the filter setup. It’s stock 2.5 1998. It’s only tube and hose what I want to use from 4.0.
 
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I'm not sure how a 4.0 intake tube is going to fit on a 2.5.

I've never heard of it being done, but I highly doubt it will fit.
 
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Thank you.

I read a lot of posts and I see cold air intakes aren’t recommended. I also started to look for stock replacement but the used stock 2.5 itself is costly.

I wanted to keep stock and thought if I could just use 4.0 hose started from throttle body and use tube to connect.

it looks like it was a bad idea :)
 
I seem to remember someone doing this a long time ago but I can't be sure. My TJ started out with a 2.5L 4cyl in it and back in 2001 when I bought it I remember a lot of talk about the stock intake tube just being a noise reduction thing. I had to lose my stock air box to be able to fit a Kilby OBA bracket and York compressor so I ran a cold air intake. But I would buy a 4.0 tube and see if it fits and if it's too noisy or not.
 
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Thank you. I guess it’s not a bad idea to try it out. :)

I Wasn’t sure because there is different cold air intake kits for 2.5 and 4.0. I don’t know the difference if it’s space or connectors.

I kinda thought if I change the throttle body in that case it should definitely fit. I soon realized throttle body isn’t just plug and play and I have very limited knowledge mechanically :)
 
Chris said:
For comparison:

4.0 intake:

View attachment 147867

2.5 intake:

View attachment 147868
Click to expand...
I don't see any issue with it fitting. You can always cut or splice it for length. My issue would be that the 4.0 is the same diameter Throttle body with the bonus of it being long and straight. The velocity of air on the 4.0 is smooth and fast. The 2.5 has 2 expansion chambers to slow the air down. I have the 2.5 and have run it without the airbox with no issues, but haven't driven it far or with a up and down hard throttle to test. I personally would like to use the 4.0 Tube keeping the stock airbox. I live in Montana where it is very dirty, dusty and very wet in the winter. An aftermarket would have an exposed filter being open to the elements and having to constantly clean it. From what I can tell the two motors are Identical except for the number of cylinders. On mine I had to replace the injectors, water pump, fan clutch, thermostat, fuel pump and steering box. Both Salesman at Napa showed all the parts were interchangeable between the 4 and 6 cylinder. Besides the 4.0 tube actually fitting I don't see why it wouldn't work except for connection.
Any Comments would be appreciated. I am new to Jeeps but have alot of experience with drag racing, motorcycle CV carbs and Dynos although about 20 year ago!
 
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Yes it can be done. You will need to use the connector sleeve that connects the silencer to the throttle body and a small piece of tubing make up the gap from the 4.0 tube being too short to reach the airbox.
 
The throttle body outer diameter of the 2.5 vs the 4.0 is the same, so no problem there.
 
Last edited:
If you decide to just go with a stock replacement, check the “for sale” forum on this thread. @Goreshnik has several early-year TJs that he parts out.
 
You could check Daveysjeep.com, or deadjeep for a stock replacement, or EBay or Craigslist for that matter.

Unless you’re wanting to go with a modified intake.

I’m sure someone on the forum will share their knowledge with their modified 2.5 intake experience.
 
Reviving an old thread.

Looking at Chris's post above that shows the 2.5 vs the 4.0. I'm wondering:
  • I learned about the 'resonator' here. But now I wonder why the 4.0 doesn't have one?
  • Now I'm also wondering about the large (expansion?) box over the throttle body. What purpose does that serve that the 4.0 doesn't need?
 
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