2.5 L with 33 inch tires

J

jasonmolinar

New member
I have a tj with a 2.5 L engine. How would it run with 33 inch tires? Or should I look into increasing the performance of the engine first? And if so, what do you suggest I use to increase the performance?
 

I am running a 2.5 with 35's, you lose 5th gear...not very good highway car....going to 37's now but doing a complete makeover.
 
I run 33's. You can run them with 4.10 gears, but forget fifth. I run them with 4.88's and still rarely use fifth (I rather cruise in 4th to avoid having to downshift all the time). I also got a couple of engine mods (see signature). I like how mine runs...
 

It's not a cheap mod by any means; I did mine a while back, and upgraded to alloy axles with ARB's and some other stuff, so I'm not much of a reference, but i should be around a grand with parts and labor... Well worth it, though.
 
If you have never seen it done, I would not recommend doing it. Plus, the cost of the tools is not worth it if you are just gonna do it once...
 
And is it all about the ratio of gears when wanting bigger tires? Or if I just decided to keep the same gears but Increase the performance of the engine what would happen?
 
jasonmolinar said:
How much of a difference will the gear change actually make?
Click to expand...

All i can say is, that ive been running 35's for the longest on stock gearing and today i had to switch back to my factory 31's cause the 35's were to the wire, anyways you wouldn't believe the dramatic change it was, im defiantly getting gears when i get new tires. i was actually able to use 5th gear,
 

There is no mod (short of installing a turbo, a supercharger, or an engine swap) that will give as much difference as a gear change; I think that's the clearest way I can put it. When I had 31's, and I switched from 4.10 to 4.88, I could put my cruise control (after market one) on, and cruise in 5th all around the greater Miami area without having to downshift, regardless of overpasses and wind, where as before, I would not make it up the overpasses in 5th, and I had to downshift anytime i was on the highway with a head wind. I would say, with that setup, i could give an I6 a run for its money.

Now, with 4.88 and 33's, it's almost back to where I was with 4.10 and 31's, which is not bad, but you will not win any awards. If you ask me, the ideal gearing for the 2.5 is 4.88 for 31's, 5.13 for 33's, and 5.35 for 35's, considerinearing, but the unsprung weight and aerodynamics)g all the changes you make (not only the mathematical gear ratio, but also unsprung weight and aerodynamics). Of course, with the stock axles, we are limited to 4.88...

Oh, and keep in mind my engine IS modded, as I have:

eFan
Performance Cam
62mm TB and Spacer
Performance ignition
High flow air filter
High Flow Cat and Cat back
Increased fuel pressure (adjustable FPR)
Larger injectors with 4 nozzles each (instead of the stock with only 1 nozzle)

None of those mods had the change that regearing did...

Hope that helps!
 

jfrabat said:
There is no mod (short of installing a turbo, a supercharger, or an engine swap) that will give as much difference as a gear change; I think that's the clearest way I can put it. When I had 31's, and I switched from 4.10 to 4.88, I could put my cruise control (after market one) on, and cruise in 5th all around the greater Miami area without having to downshift, regardless of overpasses and wind, where as before, I would not make it up the overpasses in 5th, and I had to downshift anytime i was on the highway with a head wind. I would say, with that setup, i could give an I6 a run for its money.

Now, with 4.88 and 33's, it's almost back to where I was with 4.10 and 31's, which is not bad, but you will not win any awards. If you ask me, the ideal gearing for the 2.5 is 4.88 for 31's, 5.13 for 33's, and 5.35 for 35's, considerinearing, but the unsprung weight and aerodynamics)g all the changes you make (not only the mathematical gear ratio, but also unsprung weight and aerodynamics). Of course, with the stock axles, we are limited to 4.88...

Oh, and keep in mind my engine IS modded, as I have:

eFan
Performance Cam
62mm TB and Spacer
Performance ignition
High flow air filter
High Flow Cat and Cat back
Increased fuel pressure (adjustable FPR)
Larger injectors with 4 nozzles each (instead of the stock with only 1 nozzle)

None of those mods had the change that regearing did...

Hope that helps!
Click to expand...

With those mods did you see much change (for good or bad) in your fuel mileage?
 
Not much change in fuel mileage except when I went from 31's to 33's... Then it dropped a bit. When i did the gears (with 31's, from 4.10 to 4.88), it actually weng up about 1 mpg.
 
So I know I'm probably starting to get annoying. Haha. But I bought this jeep se used. It has 31 inch tires on it and it seems to run really well. It's an automatic. And I can cruise at like 70 mph on the freeway. Is that good? Is there a simple way to check the gear differential to see if the person before me changed it?
 

Your jeep likely has 3.73 gears but if you check for a tag attached to the diff cover bolts of each axle you will be able to confirm it.

Do you know if your 70mph is with a corrected speedo or could it still be off from the change in tire size? Always best to confirm with a GPS.
 
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