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welcome to the forum. you will find lots of info on swapping a 2.5 for a 4.0. its a lot cheaper and easier to find another jeep with a 4.0.
 

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I've wheeled my 97 2.5 for years. Other than it's not so fast on highway inclines, it does just fine on the trails and moderate rock climbing.


Sent from my iPhone using Tapatalk
 

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I recently bought a 1997 TJ 4x4 with a 2.5 engine. It runs great but I feel the 2.5 is kinda weak.
Exactly what size tires are on the Jeep? You can tell from the photo they're larger than what the factory installed and the larger the tire's diameter, the worse the performance will be.

Cheaper and easier than installing the 4.0L engine would be regearing the axles to a lower ratio to match the bigger tire size, depending on what size tires they are. Regearing the axles would raise the engine rpms enough to give you more power.

It may or may not be worth regearing depending on what size tires are installed. Or if you don't care, you could install factory size tires which would restore the performance lost by the previous owner having installed larger tires.
 

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Discussion Starter · #8 ·
I recently bought a 1997 TJ 4x4 with a 2.5 engine. It runs great but I feel the 2.5 is kinda weak.
Exactly what size tires are on the Jeep? You can tell from the photo they're larger than what the factory installed and the larger the tire's diameter, the worse the performance will be.

Cheaper and easier than installing the 4.0L engine would be regearing the axles to a lower ratio to match the bigger tire size, depending on what size tires they are. Regearing the axles would raise the engine rpms enough to give you more power.

It may or may not be worth regearing depending on what size tires are installed. Or if you don't care, you could install factory size tires which would restore the performance lost by the previous owner having installed larger tires.
I actually just got gifted some Toyo tires 31X10.50R15LT A/T II. I was planning on putting on those tires on.
 

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With the 4 cyl TJ you have to keep a few things in mind; keep the tire size reasonable (33 max), use alloy (light) wheels, keep over all weight as light as possible, install lightweight accessories and keep accessories to a minimum, keep the engine running in top condition, and keep the gearing deep.

Cruise rpm's in top gear on the 2.5 should be at or very near 3000 at fwy speed. Adding taller/wider/heavier tires will kill the power by dropping rpm's out of a usable range.

If you can live with all that, be happy with the 2.5 as it is a stout little engine that will go a few hundred thousand miles with proper maintenance. If not, sell it and buy a 4.0 model.
 
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