Hey guys!
For a 2004 2.4L 4-cylinder TJ running 31x10.5r15 tires, would you install 4.56 or 4.88 gears?
For a 2004 2.4L 4-cylinder TJ running 31x10.5r15 tires, would you install 4.56 or 4.88 gears?
4.56 vs 4.88 for 31" tires on 4-cylinder
- Thread starter TJim
- Start date
Usually, Increase gears by the same % you're increasing stock tire size.
If you have a 5 speed, you may not need to change at all
If you have a 5 speed, you may not need to change at all
Fughuert
TJ Enthusiast
I was happy with 4.10 for years with 31s with my 2.5 / 5 speed, any higher and I’d run out of revs(for cruising) on the highway.
I would typically sit between 70-80 with that setup. Staying around 3k rpm.
Some people like to recommend 4.56 for 31s but I think it would suck on the highway. Unless you are the type to go 65 and that’s it, then it’d be great.
I would typically sit between 70-80 with that setup. Staying around 3k rpm.
Some people like to recommend 4.56 for 31s but I think it would suck on the highway. Unless you are the type to go 65 and that’s it, then it’d be great.
I opened a similar thread a couple weeks ago. What's your current ratio? I think 4.10 is the recommended ratio for 31" tires. Personally, I'd go with 4.56 so you can leave yourself some wiggle room if you want to go up to 33" tires. If you plan to go to 35"s down the road, go ahead and get 4.88 gearing
Rubicon88
TJ Addict
Rubicon88
TJ Addict
You must have been driving downhill.
A 4 cylinder can't maintain 70-80 mph with 31's on 5th gear.
Matter of fact it renders 5th pretty much useless.
Super flat area maybe...I stress maybe...the slightest head wind...done. incline? LOL... toast.
4.10's are OK with the 4 banger with stock 29" tires. Absolutely zero room for mods if keeping your sanity is a priority.
Go 4.88's and never look back!!! You'll be smiling roll bar to roll bar
Fughuert
TJ Enthusiast
My two phones and gps dashcam speedometers must've been broken, strange.
Fifth was entirely usable.
And we have gears for a reason, ya you downshift uphill. It's the entire reason transmissions exist.
Rubicon88
TJ Addict
You must have missed the part I said about keeping your sanity. Yep you can downshift alright...and that's all you wind up doing with that setup.
You can function with 31's and a 4 cylinder but it's a gigantic pain in the ass. I've owned them all. Rather embarrassing perhaps how many Jeeps I've owned and a 4 cylinder with stock 4.10 gears and 31's is not fun whatsoever.
The slightest adversity and you're downshifting. I mean the absolute slightest and it's down shift time...all the time.
To each their own my friend but the OP is already eyeing up a gear change...4.88's should be his target because there is absolutely zero horsepower help from the little fella and it allows a littke wiggle room like not having to use low range for everything off road...a bump to a 32" someday...not dropping to third on a long incline or failing to hold 55 mph on a 2 mile long 20 degree incline.
God forbid he ever wants to pull a small utility trailer as well.
The little 4 needs all the help it can get.
OP
What about the RPM in the highway with 4.88 - 31"? Wouldn't they be too high when travelling at70-75 mph?
Rubicon88
TJ Addict
And therein lies the problem with the 4 cylinder.
Something has to give.
Either your rpm's need increased and you have OK power from the "two foe"... or will still be on the anemic side.
There is no middle ground with it. Either you have some ok power but higher rpm or left wishing you had more power and lower rpm.
Thus the life of a 4 banger in a modified Jeep.
If you're worried about revving it..don't!!! That little 2.4 is a revving little bitch.
Gas mileage? It's a Jeep. Is it a deal breaker if you go from 17 mpg to 15.8 ?
Fughuert
TJ Enthusiast
Which is exactly why I offered my experience of 4.10's. 4.88 is unacceptably slow putting you at 67mph at 3k rpm (the 4 cylinders are happy to sit there)
I would easily maintain between 70-80 with my 4.10 gears. Usually sitting right at 78 in 5th oddly enough(GPS speedo). Ya you drop down to 70ish on bigger hills and grab fourth. It was literally a non issue. The only time I had trouble was in strong headwinds uphill, then I would get forced down to 65ish in fourth and around 70 in the flats. But oh boy was the trip home with a tail wind nice cruising at 80 no problem.
As for towing a utility trailer, I did regularly, as much as 1500lbs and it wasn't a problem either. You don't go 70+ with that much weight behind a tj, you're not wise if you do. But things like walk behind brush hogs, riding lawn mowers etc it basically felt like they weren't there and I just drove normally, non issue. The only thing I struggled towing was about 3k lbs of gravel...I had to use first gear to make it up a hill.
4.56 Is the highest I would go, based on my experience with 4.10. You'll accelerate quicker and maybe won't need 4th as much but you're still only doing 71 at 3k in 5th, which is too slow for me.
OP
