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Old 02-22-2008, 12:49 PM   #1
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Gear ratio advice for 33" tires on 4 Cylinder

Hey guys. I know this is a common topic and Iím sorry to bring it up again but Iím a newbie and canít find anyone with my exact same situation. I bought my í97 manual 4 cylinder last September and it came with 33s and a 3Ē body lift. The acceleration (or lack thereof) is killing me. When I take off from a traffic light, I feel like Iím annoying people behind me by going so slow but Iím flooring it and shifting as fast as I can. I donít think the previous owner had the spedo gear changed so Iím not sure this is correct but the speedometer says Iím toping out at 65 MPH on the highway. Iím getting another 4Ē suspension lift when I get the money so I asked the guy at the off road shop about the acceleration issue and he said I need to regear to 4.56, especially if Iím considering going to 35Ē tires. I do mostly city driving but would also like to be able to reach 85 MPH on the highway. I like to get on the trails when I can but thatís only about twice a month. Will the 4.56 gears on 33s give me the acceleration and top end speed I need or is that impossible with the 4 banger? The guy at the shop also said higher gears would improve my MPG. The labor is over $400 so I want to do it right the first time. If I need a higher ratio, I should tell them now before they install the 4.56. Are there any disadvantages to increasing gear ratio? It just sounds too good to be true that I could get everything I want out this little engine for around $1,200. I knew from the begging that I wanted the I6 engine with the D44 axles but I was in a hurry and got a good deal on this one. Any advice would be greatly appreciated.

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Old 02-22-2008, 01:05 PM   #2
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4.88 is the right gear ratio for the 2.5L/5-speed/33" tire combination, 4.56 is too high of a ratio (in ratio lingo, 4.56 is a higher ratio than 4.88 is) for the 2.5L engine. 4.56 would be ideal for 33" tires if you had the 4.0L engine but your 2.5L needs the lower 4.88 ratio... despite what whoever you spoke to at that shop said.

One more thing to keep in mind... your 2.5L TJ already has 4.10 gearing, there's just not enough difference between 4.10 and 4.56 to warrant spending the $1100-1200 cost of regearing. Go to 4.88, you won't regret it.

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Old 02-22-2008, 01:06 PM   #3
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i think the 4.56 gears would be about right for running your 33's or 35's for that matter. they will def help with our acceleration problems but i highly doubt you'd be able to go much over 70 or 75 cause the higher the gear the less top end you have. in my 4banger i have 410s with 32's and goin 70 im already running 3K rpm. the 4.56's will def help out on the trail, thats what im plannin on gettin in the summer
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Old 02-22-2008, 02:58 PM   #4
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So if I get a lower gear ratio (thanks for the correction Jerry) like a 4.56 or 4.88, they'd replace the gears in my transmission and not my differentials, right? So the tag on my diffs will always say 3.07 even though I'll actually have a lower ratio? If I lower the ratio in the transmission, will it put extra strain on the diffs and axles? Do I have to get the Dana 44?
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Old 02-22-2008, 03:01 PM   #5
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With a 4cyl you should have 3.73 or 4.10 gears stock in the axles. And when you regear, you only change the gears in the axles not the transmission.
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Old 02-22-2008, 03:43 PM   #6
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And when you regear, you only change the gears in the axles not the transmission.
True. Regearing means you are changing two gears called the ring & pinion gears inside both the front and rear axles. It's a pretty demanding job that is best left up to a mechanic who is experienced and good at doing ring & pinion installations. Regearing both axles will normally cost $1100-$1200 which includes all parts and labor for both axles.
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Old 02-22-2008, 04:21 PM   #7
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I also agree with the 2.5/33's and 4.88 combo. I've driven 4 bangers with both 4.56 and 4.88 and you'll be much happier in all conditions with the deeper 4.88's.
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Old 02-23-2008, 10:36 AM   #8
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Awesome. Thanks guys. I think I'll go with the 4.88 since I might move up to 35" tires one day. Is there a big price difference between the 4.56 and the 4.88? If not, I don't see why everyone wouldn't just go as low as possible with their gear ratios.
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Old 02-23-2008, 10:47 AM   #9
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4.88's will be good for you, i don't think its much a difference in price, if at all.... be careful if you go with 35's if you don't have d44's, at least in the rear, i've heard it can be too much tire for our little 35's
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Old 02-23-2008, 06:56 PM   #10
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I have a 97 4 banger and 4.88's. Trust me go to at least 4.88 unless you can get d44's then go deeper. BTW with 4.88's and 33's my stock speedo gear is now accurate again.
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Old 02-25-2008, 07:08 AM   #11
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I have a 97 4 banger and 4.88's. Trust me go to at least 4.88 unless you can get d44's then go deeper. BTW with 4.88's and 33's my stock speedo gear is now accurate again.
X2. 97/4.88/44's here too with manual transmission. I compared my speedo to my GPS and it was only 1 mph off. I've wheeled and DD'd my TJ in this setup for 2 years now and it I've been VERY pleased with it offroad and satisfied onroad. It still won't fly down the highway, but I can hold speed much easier than I could at 4.10 (but I also have quite a bit of armor, bumpers, winch, etc weight to factor in).
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Old 02-25-2008, 06:19 PM   #12
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I have a 97 4 banger and 4.88's. Trust me go to at least 4.88 unless you can get d44's then go deeper. BTW with 4.88's and 33's my stock speedo gear is now accurate again.
Is it an auto, and what rpm at 70mph?
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Old 02-26-2008, 04:05 AM   #13
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4.88's will be good for you, i don't think its much a difference in price, if at all.... be careful if you go with 35's if you don't have d44's, at least in the rear, i've heard it can be too much tire for our little 35's

Yup, 33's on a stock dana 35 is where you start to see axle and spider gear breakage. May want to consider a super 35 kit, or a dana 44 upgrade.
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Old 02-26-2008, 07:50 AM   #14
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Yukon 35 kit here with alloy 30 spline shafts and ARB locker in back. Lockright in front. No way was I going to run 33's on a D35 stock, even with the 2.5L engine.
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Old 02-26-2008, 09:25 AM   #15
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Is it an auto, and what rpm at 70mph?
no mines a 5 speed and I am right at 2750 I believe, I will double check that this afternoon.
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Old 02-26-2008, 01:12 PM   #16
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no mines a 5 speed and I am right at 2750 I believe, I will double check that this afternoon.
With 4.88 gearing, 33" tires, and the 5-speed, I'll bet it's a little closer to 2950-3,000 RPMs. My engine was spinning right at 2750 RPMs at 70 mph (and it is dead-nuts on) with 4.88 but with 35" tires. And with the 2.5L engine, you want/need those slightly higher RPMs to successfully run 33" tires.
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Old 02-26-2008, 01:59 PM   #17
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If you are looking for a little more pep out of you engine upgrade to the I6 throttle body
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Old 02-26-2008, 05:34 PM   #18
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no mines a 5 speed and I am right at 2750 I believe, I will double check that this afternoon.
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With 4.88 gearing, 33" tires, and the 5-speed, I'll bet it's a little closer to 2950-3,000 RPMs. My engine was spinning right at 2750 RPMs at 70 mph (and it is dead-nuts on) with 4.88 but with 35" tires. And with the 2.5L engine, you want/need those slightly higher RPMs to successfully run 33" tires.
I checked it this afternoon, and it is right at 3000 rpm's at 70.
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Old 02-26-2008, 06:01 PM   #19
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I checked it this afternoon, and it is right at 3000 rpm's at 70.
Thanks, anyone know if it will be higher or lower in an auto?
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Old 02-29-2008, 10:18 AM   #20
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If you are looking for a little more pep out of you engine upgrade to the I6 throttle body
i thought about that but you only get like 4 or 5 more HP from the I6 TB, right? i priced the larger TB for the 2.5L in the 4WD catalog and they were like $300. that's pretty pricey for a relativly small gain and i don't have the expertise to get one from a junk yard and mill it myself.

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