Is it recommended that you replace your 4 cylinder engine with a 6 cylinder to go bigger on tires and lift, and is it difficult?
Should I replace my 4 cylinder engine to run bigger tires?
- Thread starter Tiffany LeBlanc
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TJ Enthusiast
In all reality you can use the same engine just regear for the tires. Dirt every day has a Jeep names tube sock. That started as a 4cyl they ran 37s on it just fine. Now of course they did bigger axles but gearing was key to good performance.
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Yeah, I don't think Tube Sock spent much time on 37s with the stock 2.5L!
To answer @Tiffany LeBlanc 's question...No, you don't need to change the motor to lift and / or run bigger tires. Just need to get more gear (numerically higher numbers)
How big do you want to go?
To answer @Tiffany LeBlanc 's question...No, you don't need to change the motor to lift and / or run bigger tires. Just need to get more gear (numerically higher numbers)
How big do you want to go?
Alrighty then. Time to be controversial!
In my opinion the 2.5 tops out at 32 to 33" tires. After that you need axle swaps, transmission swaps, all the suspension work to fit your tires and terrain, etc. I love me some SE's, but there is a practical upper limit to how big you can go without getting into major modifications.
As for an engine swap to the 4.0, it's almost easier and cheaper to go Chevy V8 instead of Jeep 4.0.
In my opinion the 2.5 tops out at 32 to 33" tires. After that you need axle swaps, transmission swaps, all the suspension work to fit your tires and terrain, etc. I love me some SE's, but there is a practical upper limit to how big you can go without getting into major modifications.
As for an engine swap to the 4.0, it's almost easier and cheaper to go Chevy V8 instead of Jeep 4.0.
OP
4.88 or 5.13 gears, upgraded 27 spline alloy axles and drive it in a reasonable manner should work just fine on the street and for mild off road. Anything more abusive will require a locker of some type so you can upgrade to larger 30 spline axles.
OP
Im sorry I dont know what you mean when you say gearing, or what gear I will need.
He means to say that you'll need new ring and pinions for the front and rear axle. This isn't required by any means, but when going up in tire size, it will make a huge difference in the way the vehicle performs. Adding larger tires without changing the ring and pinion (or re-gearing as we call it), will make for an extremely sluggish vehicle, especially when it comes to off-the-line performance. The added size and weight of the larger tires really bogs down the engine. A re-gear will fix that.
By gearing, we are talking about the physical gears in your front and rear axles. Also gearing is the final drive ratio.
With your current 4.10 ratio, the engine turns about four times for every one time your tire turns. When you go to a bigger tire, you want the engine to turn more than that so your economy and power don't decrease. By physically changing the gear ratio to a numerically larger number this happens. With a 4.88 or 5.13 ratio, the engine turns about five times for every time the tire turns. As a side note, your speed is kind of the same because the bigger tire travels further each time it goes around. Make sense?
So, your engine drives the wheels through a transmission (the thing you shift) and then to the rear axle. In order to make the wheels roll forward or backward, the power needs to "turn a corner" if you will. In other words, the engine, being arranged as it is, spins counter clockwise as you look at it from the drivers seat. If you were to let it move, while its in that orientation, it would go left. Follow?
Now, since we want our tires to roll forward and backward, we need to take that rotation and "turn" it so that it faces forward and backward. That is what the "gears" do. When we are saying gears, we are really talking about a ring and pinion. That allows the rotation to turn the corner. Here is a nice drawing...
here is an article that will explain it too...
http://www.hotrod.com/articles/how-gear-works/
OP
Gearing depends on engine, transmission, and tire size. With 33's, a 4 banger, and (I'm assuming) a 5 speed, I wouldn't go any less than 4.88, maybe even 5.13. Picking between those two will come down to how you use the jeep. Go 4.88 if you do a lot of highway driving. 5.13 will give you some more grunt, but the engine will be running up pretty high once you get up to highway speed.
Just for reference, I went with 4.56's with for 33's and a 4.0.
@StG58 has the answer in post #8 above. You need 4.88 or 5.13 gear ratio, as well as upgrading your axles to 27 or 30 splines. A re-gearing shop knows what all this stuff is. It will probably cost around $1600-2000. You would need to do the same thing if you had a 4.0 rather than the 2.5, so the engine is not the issue when you're biggest tire size is 33's. Also, what are you going to be using the Jeep for? Is this on-road only or off-road too?
Again, you'd re-gear in order to regain the performance of your Jeep when you add bigger tires. The main reason is the bigger tires have a bigger circumference than your stock tires. The gears can be changed to accommodate for that bigger circumference and will restore your Jeeps peppiness. Otherwise, it will drive like a slug!
Again, you'd re-gear in order to regain the performance of your Jeep when you add bigger tires. The main reason is the bigger tires have a bigger circumference than your stock tires. The gears can be changed to accommodate for that bigger circumference and will restore your Jeeps peppiness. Otherwise, it will drive like a slug!
Math, experience and a little magic. There's charts out there that will tell you a recommended gear ratio, that's the math part. The charts usually use tire size and speed to determine a recommendation. There's more to it than that though. How you use your rig, where, the transmission...that where the tribal knowledge here comes in. The charts will get you close. The common pool of experience will get you even closer, if not right on.
With the right gears its more than possible to run a larger tire on a 2.5L. A friend of mine runs 36" tires on heavy steel beadlocks without issue. Admitted he's no longer running the stock axles but it really comes down to his getting choice.
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There must have been a time
when we could have said no.
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There must have been a time
when we could have said no.
My 2.5 has an automatic and 3.73:1 gearing, 31" tires. that gear ratio suits my situation for now cuz my 97TJ is my daily driver. I live in a rural area, have to do more highway driving than city so the 3:73 will stay for now
First off, forget the engine swap. Buy another Jeep if you really want the 4.0.
If you are set on 33's, you will need to invest in a gear swap. The differential gears are inside the front and rear ends that turn the axles which turn the wheels. They are identified by their ratio; 3.73, 4.10, 4.88, etc. Meaning the pinion turns that many times to one time of the ring gear. The bigger the number, the lower the gearing, the more "power" the Jeep has to move itself.
With larger tires, you need lower gearing, especially with the 4 cylinder engine. The larger diameter tire along with the extra weight requires lower gearing than stock to keep momentum, ie speed up.
For your particular future combo I would recommend 5.13. This means new gears front and rear, bearings, seal, and maybe some other parts depending on condition of the differentials. It will not be cheap, probably 1500 or so to do the job.
If you are set on 33's, you will need to invest in a gear swap. The differential gears are inside the front and rear ends that turn the axles which turn the wheels. They are identified by their ratio; 3.73, 4.10, 4.88, etc. Meaning the pinion turns that many times to one time of the ring gear. The bigger the number, the lower the gearing, the more "power" the Jeep has to move itself.
With larger tires, you need lower gearing, especially with the 4 cylinder engine. The larger diameter tire along with the extra weight requires lower gearing than stock to keep momentum, ie speed up.
For your particular future combo I would recommend 5.13. This means new gears front and rear, bearings, seal, and maybe some other parts depending on condition of the differentials. It will not be cheap, probably 1500 or so to do the job.