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2.5 4 cylinder. why do a lot of people hate

27K views 50 replies 24 participants last post by  Mykl87yj 
#1 ·
Why do a lot of people hate on the 4 bangers
 
#2 ·
I don't think anyone actually hates the 2.5l, they just tire of seeing the questions from people about how to run 33"+ tires from an engine that had to be backed by 4.10 gears from the factory just to maintain highway speeds with 27" tires.

The 2.5l engine is a perfectly fine engine if you don't plan on running anything larger than a 30" tire, but the engine is a car engine stuffed into a brick, it doesn't put out the torque an engine needs to move a Jeep, even the 4.2l / 4.0l starts to putter out in stock form with 33's and anything smaller than 3.73 gears.....lots of people out there want to improve the performance of this engine and they think that keeping the 2.5l is the most cost effective method, when in actuality your best (and cheapest route) is to toss in a readily available 4.0l/AX15/NP231J combo....and your fuel mileage rarely actually suffers from the swap.
 
#4 ·
If you are going to step up to tires that size and swap gears in the ford 8.8.....I would recommend that you upgrade the trans to an AX15 and go with 5.13 gears instead of the 4.88.

33's and 4.88 will put you back to stock performance with the AX5, the 5.13/AX15 will give you more strength and better bottom end gearing, the steeper OD on the AX15 will compensate for the lower gears. Either combination might be a bit of a stretch for regular 5th use on anything but flat ground.

Gear Ratio Calculator <--- Great site for a breakdown of stock vs. the suggested setups above (215/75/15 tires are stock) Pay special attention to the road speeds at 3,250RPM....that is the tq. peak of the 2.5l +/- 250 RPM of this range is where I would typically run in each gear before shifting.
 
#6 ·
I don't think that I actually hate a 2.5L. They are good capable engines. I just don't like them very much because I owned one. I have the experience of never getting in the left lane, and being passed all the time on a 2-lane highway. And I had all of the proper equipment installed. Deep gears, 4.0 throttle body, bigger injectors, electric fan, you know, all the mods that make you think you are getting more out of it.

The biggest problem that I had with the 2.5L was once I installed a 4" lift and 33" tires, and 4.88 gears. I found out that the tires were too heavy for the 4 popper to spin if you got in a deep hole. No horsepower is no horsepower. Period.
 
#7 ·
People hate 4cyl because they try to do stuff to them without researching them first... The 4cyl is underpowered for upgrades... lightduty AX5 and weak axles... I dont hate my 4cyl anymore because I dropped my tire size to stock 2157515 I can pull hills in 5 gear and run 70-75 no problem if I wanted... I keep my speed down due to much reduced fuel economy at 70 plus MPH. We are driving a flying BRICK... A 4cyl stock YJ is a great vehicle keeping it stock... If anyone wants to run big tires and mods always go with a 6cyl ... JMO.
 
#12 ·
This ^ and then as 0llll0 sad the lack of power for upgrades

I get about the same with my 4.0 and 33's and have more POWER, that's why I don't like the 2.5
I get about 16 mpg highway (adjusted for the tires) with 33s and 3.07 gears with my 4.0. I'm not sad I waited and got a 4.0. The 2.4 is a good motor and is equal to the 4.0 when crawling around offroad IMO
 
#8 ·
I have a 2.5 AX-5 with 4.10 gears on 33x12.50 tires and am happy with it. Jeeps were never intended to be highway cruisers 55 mph is comfortable here in Florida and that is plenty fast enough. If you have to deal with steep grades or larger tires then the 4.0 or 4.2 is the way to go. Engines of this very design are used in boats with great success and are very reliable. The only thing I can find really wrong with the 2.5 is not the motor but the inferior transmission they saddled it with.
 
#10 ·
Just another data point. I can hit 70mph+ in my 2.5, that's with 33s and 4.88 gears. I can even go faster but I give up around then.

I can also climb the hills heading towards Rausch at 70mph. Of course that's in third gear with the engine screaming but she did it.

No, it isn't ' sports car and I do wish I had the 6 but the 4 isn't horrible. Oh, and 19 mpg @ 55mph isn't too shabby either.
 
#13 ·
My 4.0l gets an average 18mpg on the highway running at 70~75mph in 4th gear (3.08 gears in the axles). I have held 55mph for a prolonged period of time, and didn't see any better mpg (still 18).....my 3.08's also average 16mpg in town.

When I upgrade to 4.10's I should be able to use 5th and maintain the same RPM and speed (and hopefully the mpg).

DSHroka, I assume you meant the cost for an AX15? There is a big range for that, if you upgrade to the AX15, you will also need to swap your transfercase (different input spline count). I would imagine the total swap (new clutch, new slave, used trans/xfer and driveshafts) would probably cost less than $1,000.
 
#14 ·
Many of us (me included) hate the 2.5L because it's underpowered, and caused us to do an engine (actually entire drivetrain!) swap.

They are plentiful and relatively cheap (compared to 4.0l jeeps), but I'd recommend that anyone purchase a 4.0L Jeep. You also get the stronger AX15, as mentioned above.
 
#15 ·
I got me an 89. 2.5. All original. Hell just replaced factory starter. No rust. 65k miles. I bought it to upgrade. But im ad military so i post trying to get off riad worthy for cheap. Every post is like 2.4 sucks heres
 
#18 ·
Best bet for offroad worthiness for a 2.5l is to go with a 2.5" lift and 30" tires. That will give you some ground clearance and make all but 5th gear usable.

With the 2.5" lift you probably won't need the transfercase drop, only axle shims, you will get decent flex and have no issues with tire rub. A ubolt kit will help make up a small amount of the ground clearance you loose by not being able to run 33's.

I would make the AX15 my first upgrade....it is a foundation that will support all of your future mods (bit it power upgrades, tire upgrades, or a 4.0l swap).
 
#21 ·
I USE to not care much for them simply for their lack of power. I've always had the 4.0 in my previous YJs and my dad's 87 had the 4.2. It's funny, tho, the 2.5 has 123 hp, when my dad's 4.2 only had 112. Lol. But the 4.2 had much better torque which is what matters when talking about turning the tires.

But a friend of mine has a 92 he bought 15 years or so ago with 120k miles on the 2.5. It's now got 320. Lol. Never been rebuilt even. Just maintained very well. He runs 31s but with 4:88 gears.

So I went out and bought a 95 Rio Grande which only came with the 2.5. 29 inch tall tires (235 75 15), and a 5 speed, and I drove it home, 80 miles, from where I bought it with 198k miles, and it easily maintained 70 mph. Unless I was passing a semi. Lol. Then the draft slowed it down. Lol. But I've gained a newly found respect for the 2.5.
 
#26 ·
I know this is an old thread- but here is my
Experience.
My first YJ was a 92 while living in western Pa. Moderate hills mostly flat also, highway speed limit was 65 you were risking a ticket at 72.
Now I live in Arizona(Phoenix) which is mostly mountains at least 15 percent grade highways. Speed limit is 75 highways 65 in the city- very common to see guys doing 90 on the highway and 80+ in the city. So I recently picked up a 95 2.5 with a 3 inch lift on 33s stock gears. As long as I have the gas hammered down I can maintain 75 in the city. When I took a trip up to Flagstaff it really struggled up the inclines..going from 700 ft about sea level to 3500 ft in a few miles. But to be fair every car will struggle a bit. At least I could plant myself between two semis in the right lane and chug along.
As far as off-roading..for me it's just fine. I do intend on upgrading the engine once it goes on me. If ever decides to die.
 
#27 ·
old threads are made to be restarted

First post on this forum so i may as well comment on an old thread..my 2.5 has had it's ups and down literaly. After hydrolocking two of them I am on my last one before I swap however I have never had power issues on trails with my 4" lift or my 33's.. Highway speed is 65 max which is adequate and the box just looks better sitting up higher so i dont mind much about the 16mph :beerme:
 
#31 ·
i sucked up water twice and 1st time just drove it till the side exploded out..put another in and got too deep in a creek, pulled the plugs to cough the water out, and made it 3 days till the dang moter exploded again...on my 3rd and final 2.5 and been real careful to keep the water level (and intake) from having intercourse...:)
 
#32 ·
Its the lack of power, when I bought a 4.0L, the difference was phenomenal...

Of course, I did end up quickly grenadeing my Dana 35 trying to race a Cummins....
Ended up with a 8.8, another night and day difference (do not get a Spartan, get a select-able locker)....
 
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