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Old 12-24-2008, 11:49 AM   #1
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33's and 4.88's

I am planning on bumping up to 35" tires this year and upping my gears to 4.88s to go along with the bigger tires. After doing some research, I've decided to add an Ox locker to the front axle at the same time. Problem is, I only have enough cash to do two of the three things. I already have the gears, so the question is: do I have them installed with the locker? Or do I just have the gears installed and get the bigger tires? It makes sense to me to save $ on labor by doing the gears and locker at the same time.

My big question is: Has anyone run 33" tires with 4.88 gears? (I have the 4 speed auto transmission.) This is my daily driver so it has to stay freeway able. What is the impact of doing this? Should I just let the gears and locker sit on my workbench 'till I can afford the 35's and do it all at the same time?

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Old 12-24-2008, 03:29 PM   #2
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33 with 4.88 gear will severly affect your highway speeds.. ur tranny is going to be screaming

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Old 12-24-2008, 03:30 PM   #3
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as long as you dont go over 45 mph on ur regular daily commute you should be fine...
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Old 12-24-2008, 03:48 PM   #4
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33" tires with 4.88 gears will produce higher than optimal engine rpms but for temporary use until you get your 35" tires, it'd be fine. I have the same issue with my TJ since changing my 5-speed manual to a 3-speed automatic transmission but it's really not bad at all. I'm now cruising at 3000 rpms at around 70 so I slowed down to 60-65 but when I need to do 70-75 or even higher to pass on the highway, the rpms are higher than optimal but still ok.
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Old 12-24-2008, 03:50 PM   #5
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X2 but dont expect to go down the highway being geared that low. I had 4.56's and 33's with my 5 spd and it kinda sucked. I would turn 3K rpm the whole trip which killed my gas mileage. I always liked higher gearing over low just because it makes the freeway more comfortable and then just use 4 Lo when wheelin. But thats me. I just wouldnt suggest freeway on that tire/gear combo.
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Old 12-24-2008, 03:56 PM   #6
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Originally Posted by GrnTJ View Post
I had 4.56's and 33's with my 5 spd and it kinda sucked. I would turn 3K rpm the whole trip which killed my gas mileage.
You weren't turning over 3K with that combination at even 70 mph speeds so long as your speedometer was properly calibrated. At 70 mph, that combination would give more like 2600 rpms with 4.56 and a 5-speed transmission which gives very good all-around performance. 4.56 is actually the recommended ratio for 33" tires and the manual transmission. Only if you were used to a car's much lower rpms with tiny tires would you possibly consider the rpms of 4.56 with 33" tires and manual transmission excessive.

Here's a good chart to calculate speeds and rpms with different transmissions, axle ratios, and transmissions... http://www.manoian.net/jeep/gear_ratio_calculator.html

That calculator says you'd have to be driving nearly 82 mph to get 3000 rpms on the tach with 33" tires, 4.56 ratio, and an AX-15 or AX-5 transmission like came in the '99 TJ. Not exactly a recommended or legal cruising speed in most states.
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Old 12-24-2008, 04:12 PM   #7
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Jerry, I like to run down the highway between 70 and 75 and my rpms were always between 2800 and 3150. My speedo was caliberated and I know what Im saying and I realize 4.56 is "recommended" for that set up. What Im saying is that Id prefer slightly numerically lower gearing over what is suggested because for 2 years I drove my ZJ with 3.73's on 33's which kept my rpms very low. It didnt launch at a green light or anything but its a jeep so i didnt care. When I put it in 4 Lo it climbed just fine too. Basically Im saying if I had the choice Id go with slightly higher gearing than what is "recommended" for a certain set up. I have never in my life owned a "car with tiny tires" so please dont assume things like this when you dont really know me or my vehicle history. Everyone likes their rigs a certain way and I prefer mine to have lower than than normal rpms at highway speeds. Im not trying to be rude so I hope you dont take offense.

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