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Old 06-07-2010, 01:09 PM   #1
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Gear, Tire Size and RPM ?

Need Help and want true RPM not some chart in a book ! I have 2000 TJ 6cyl and 5 speed with 3.07 gearing and 32's. Gear change comming really soon and I want to know what gear to get without turning to hight RPM at 70mph.
Right now I turn around 1500/1600 in 5th at 70

Tell me your set up and RPM at 65 to 70 .


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Old 06-07-2010, 01:25 PM   #2
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use this for calculation: Engine RPM Calculator

use this to get your tranny gear ratio: Stock TJ Specifications - JeepForum.com


This will let you know whats what. Let me know if you have any questions

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Old 06-07-2010, 01:39 PM   #3
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Thanks ! Cool links . Works out to about 2400 at 70 with 4.11 I can live with that.
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Old 06-07-2010, 01:44 PM   #4
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im guessing you have dana 30 front and dana 35 rear diffs right? You can do an easy upgrade to 4.10 gears for about 550 bucks..not including labor. 4.10 gears and front and rear dana 44 diffs is one of the main reasons why I got a rubicon.
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Old 06-07-2010, 01:44 PM   #5
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Be aware that the bigger the tire, the more RPMs you need to maintain adequate performance. An RPM that is adequate for 30" tires would not be enough for 33" or 35" tires. And 2400 RPMs at 70 mph is barely adequate for larger tires. Plus do you think you may ever get to 33" tires? If so, I would regear to 4.56 with your 5-speed and 4.0L engine.
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Old 06-07-2010, 03:05 PM   #6
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Be aware that the bigger the tire, the more RPMs you need to maintain adequate performance. An RPM that is adequate for 30" tires would not be enough for 33" or 35" tires. And 2400 RPMs at 70 mph is barely adequate for larger tires. Plus do you think you may ever get to 33" tires? If so, I would regear to 4.56 with your 5-speed and 4.0L engine.
What kind of RPM do I need to turn to be in a good cruise range and not bog down motor ? I don't want to be down shifting to much . I plan on staying with 32's or the most 33's. I was just worried about turning to many rpm's while on freeway or highway. I haven't owned a Jeep before and don't want to over work motor.
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Old 06-07-2010, 03:13 PM   #7
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im guessing you have dana 30 front and dana 35 rear diffs right? You can do an easy upgrade to 4.10 gears for about 550 bucks..not including labor. 4.10 gears and front and rear dana 44 diffs is one of the main reasons why I got a rubicon.
Yes I do have D30/D35 set up. I am going to try to upgrade at a later date to the 8.8 rear or find used Dana 44. I just bought Jeep a month ago and am really enjoying spending money on upgrades. Gears seem to be something I can't or wont live without . Original owner had it stock except 2" lift and tires and wheels.
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Old 06-07-2010, 03:23 PM   #8
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What kind of RPM do I need to turn to be in a good cruise range and not bog down motor ? I don't want to be down shifting to much . I plan on staying with 32's or the most 33's. I was just worried about turning to many rpm's while on freeway or highway. I haven't owned a Jeep before and don't want to over work motor.
The 4.0L engine doesn't need high rpms but you don't want it to be bogged down in lower rpms either. When I had my 5-speed and went with 35" tires, I geared it to 4.88 which produced around 2700 rpms at 70 mph which over several years of use, I was happy with how it ran. Those rpms seem high to anyone coming from a car but for a Jeep with big tires and the aerodynamics of a barn door, they aren't too high at all. You of course don't need 2700 for 32" or 33" tires but for bigger than stock tires, I'd like to be at least 2450-2500 at a minimum for 32-33" tires. If you know (!) you will never install a tire bigger than 32", 4.10 is fine. But if you know deep down you'll eventually get to 33", I'd regear to 4.56 so it will be optimal for 33" tires.
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Old 06-07-2010, 03:40 PM   #9
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Can't and won't say never to bigger tires so 4.56 it will be. Thank you for your help. I should have got a jeep years ago .
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Old 06-07-2010, 03:51 PM   #10
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Incidentally... if this will make you feel better about 4.56 for 32" tires, Jeep shipped the TJ version of the Rubicon with 4.56 gears for its OE 31" tires.
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Old 06-07-2010, 04:28 PM   #11
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I run 39s on 5.86s @ 2800 RPM @ 65MPH.
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Old 06-08-2010, 08:28 AM   #12
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Quote:
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Incidentally... if this will make you feel better about 4.56 for 32" tires, Jeep shipped the TJ version of the Rubicon with 4.56 gears for its OE 31" tires.
I have to disagree with you there about the Rubicon's (TJ) stock gears and tires.

2003-2006 TJ rubicons were stock with 4.10 gears and LT245-75R16 Tires (30.5 inches) I own a 2003 rubicon and thats what the sticker in the doorwell says plus ive done alot of mad research on this because I plan on going up to 31's and the 4.10 gears will be just fine for that.
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Old 06-08-2010, 08:51 AM   #13
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My bad...i was thinkin about manual trannies. I dont consider automatic jeeps "real" jeeps :P the autos did come with 4.56 gears
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Old 06-08-2010, 09:04 AM   #14
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I dont consider automatic jeeps "real" jeeps :P
Ya see more rock crawler Jeeps with auto's rather than manuals, so that doesn't make a Jeep not a "REAL" Jeep.
IMO, the only Jeeps that aren't "REAL" Jeeps, are the Mall Crawler Jeeps, be it manual or auto, that have only ever seen road dirt and don't have a single bit of trail pin stripping on them!!

If it's wheeled, it's a Jeep.
If it's a Mall Crawler, it's a waste.
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Old 06-08-2010, 09:43 AM   #15
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Ya see more rock crawler Jeeps with auto's rather than manuals, so that doesn't make a Jeep not a "REAL" Jeep.
IMO, the only Jeeps that aren't "REAL" Jeeps, are the Mall Crawler Jeeps, be it manual or auto, that have only ever seen road dirt and don't have a single bit of trail pin stripping on them!!

If it's wheeled, it's a Jeep.
If it's a Mall Crawler, it's a waste.
I knew I'd get a rise out of someone for that comment lol. I say it in jest btw I just like the fact I can control my gears as im wheelin plus the RPM's of each gear ratio. Maybe its just me but I dont see the point in automatics...im guessing it makes crawling up rocks easier...but doesnt that defeat the purpose of offroadin?>> :P
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Old 06-08-2010, 10:15 AM   #16
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I have to disagree with you there about the Rubicon's (TJ) stock gears and tires.

2003-2006 TJ rubicons were stock with 4.10 gears and LT245-75R16 Tires (30.5 inches) I own a 2003 rubicon and thats what the sticker in the doorwell says plus ive done alot of mad research on this because I plan on going up to 31's and the 4.10 gears will be just fine for that.
A 30.5" tire is considered a 31" tire. Look at the actual diameters of tires sold as a 31" like a 31x10.50 and you will see they are all in the 30.5 or so size range.
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Old 06-08-2010, 10:19 AM   #17
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I knew I'd get a rise out of someone for that comment lol. I say it in jest btw I just like the fact I can control my gears as im wheelin plus the RPM's of each gear ratio. Maybe its just me but I dont see the point in automatics...im guessing it makes crawling up rocks easier...but doesnt that defeat the purpose of offroadin?>> :P
Go to a competition like a rock crawling championship and you will discover that most hard core wheelers long-ago switched to automatics.

It is usually the newbs who think manual transmissions are the way to go for the most difficult trails. It's actually the other way around. Manual trannies are fine for beginner to moderate-level trails with automatics being better for the more hardcore trails. Autos give 2-3X more (yes) low-end torque and they provide better control on the extreme level trails.

You would be hard pressed to find a manual transmission in a serious competitor's vehicle any more. The race/rock crawl vehicle I had a small part in helping to build for last year's King of the Hammers race/rock crawl event had an AW4 automatic transmisssion in it.
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Old 06-08-2010, 10:30 AM   #18
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Go to a competition like a rock crawling championship and you will discover that most hard core wheelers long-ago switched to automatics.

It is usually the newbs who think manual transmissions are the way to go for the most difficult trails. It's actually the other way around. Manual trannies are fine for beginner to moderate-level trails with automatics being better for the more hardcore trails. Autos give 2-3X more (yes) low-end torque and they provide better control on the extreme level trails.

You would be hard pressed to find a manual transmission in a serious competitor's vehicle any more. The race/rock crawl vehicle I had a small part in helping to build for last year's King of the Hammers race/rock crawl event had an AW4 automatic transmisssion in it.
hehe good thing im not hardcore :P I just like the fact i can control my gears. I'm sorry if I offended you and your automatic transmissions. I wasnt trying to call you a girlie-crawler. I was just trying to be funny..Please dont think that I think you can't operate a manual transmission properly... I'm sure automatic trannies have their uses..I just find them boring very boring...just MVHO..
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Old 06-08-2010, 11:37 AM   #19
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hehe good thing im not hardcore :P I just like the fact i can control my gears. I'm sorry if I offended you and your automatic transmissions. I wasnt trying to call you a girlie-crawler. I was just trying to be funny..Please dont think that I think you can't operate a manual transmission properly... I'm sure automatic trannies have their uses..I just find them boring very boring...just MVHO..
Just to be clear, I have been driving manual transmissions for just over 44 years. They have their place like in sports cars and big trucks. If I were buying a Porsche, I would not even consider an automatic transmission. But once my TJ was doing 5+ rated trails out in Johnson Valley, I converted it from its OE 5-speed to an automatic to take the Jeep up to the next level. Converting it to an automatic gave it as much of a boost in hardcore trail abilities as converting from Truetracs to front and rear lockers did.

Come wheeling to me and you'll see where an automatic shines. It's not about manhood needing a stick shift to feel virile, it's about what works best on the most hardcore trails.
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Old 06-08-2010, 12:31 PM   #20
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My bad...i was thinkin about manual trannies. I dont consider automatic jeeps "real" jeeps :P the autos did come with 4.56 gears
Really?
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Old 06-08-2010, 12:43 PM   #21
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holy god!!! it was a joke...if you feel so inadequate about running an auto tranny...their is a solution...
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Old 06-08-2010, 01:12 PM   #22
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holy god!!! it was a joke...if you feel so inadequate about running an auto tranny...there is a solution...
Who in this thread first made the comment saying real Jeeps don't come with automatics? You did. There's no feelings of inadequacies, you simply need to understand that not everyone thinks your comment that an automatic equipped Jeep is not a "real Jeep" comment was funny. Why? Because it's a tired overused phrase that too many newbies throw out without any thought behind it. If you think I'm feeling inadequate, let's take our Jeeps out and you try to follow me on the trails I enjoy (check out my website, below).

And if you go to 31" tires that you think will be an inch bigger than what came on your Rubicon, be prepared for a shock, they will actually be barely taller than your present 245/75R16 tire size... like 1/10" taller Goodyear's 245/75R16 tire is 30.7" tall and their 31" tire is only 30.8". With a 17" wheel, they are exactly the same size.

Even with different brands, a 31" is very similar in size to the Rubicon's OE 245/75R16 tire.
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Old 06-08-2010, 01:22 PM   #23
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Who in this thread first made the comment saying real Jeeps don't come with automatics? You did. There's no feelings of inadequacies, you simply need to understand that not everyone thinks your comment that an automatic equipped Jeep is not a "real Jeep" comment was funny. Why? Because it's a tired overused phrase that too many newbies throw out without any thought behind it. If you think I'm feeling inadequate, let's take our Jeeps out and you try to follow me on the trails I enjoy (check out my website, below).

And if you go to 31" tires that you think will be an inch bigger than what came on your Rubicon, be prepared for a shock, they will actually be barely taller than your present 245/75R16 tire size... like 1/10" taller Goodyear's 245/75R16 tire is 30.7" tall and their 31" tire is only 30.8". With a 17" wheel, they are exactly the same size.

Even with different brands, a 31" is very similar in size to the Rubicon's OE 245/75R16 tire.
easy there tiger...I take it back...I really didnt mean to hit a nerve there..but I guess i did. "to each their own" is my saying. I never claimed to be some great rock-crawler like you claim to be. I was just stating my opinion. I'll never make that mistake again on this forum.
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Old 06-08-2010, 02:01 PM   #24
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Geez

Alright gents, Texas was just asking for advice. But I want to clarify something. I'm looking for a DD, our second jeep, in auto 4.0, probably 2000ish. I'm thinking 32-33's, our 99 has 31's, will re-gearing be needed? Mainly on-road, hwy, very little off-roading honestly.
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Old 06-08-2010, 02:29 PM   #25
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Due to the automatic's torque converter, you can get away with larger tire sizes with an automatic than you can with a manual. There is a big change in the automatic starting with the 2003 model year. 2002 and older uses the 3 speed 32RH transmission, 2003 and newer uses the 4-speed 42RLE transmission. The 32RH is a bit more "robust" but the 42RLE has an overdrive. However, rpms will be pretty low on the highway with 33" tires with the newer 4-speed automatic. If you don't want to have to regear, perhaps the 2002 and older would be good as your highway rpms would be high enough to run the 33" tires. A 2003 or newer with the 4-speed would be a better choice but you'd really want to regear to 4.88 for 33" tires for best all-around street and highway performance.
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Old 06-08-2010, 02:35 PM   #26
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Not to stir the pot, the reason I like an automatic in my tj is cause I'm a truckdriver double clutching a 13 speed, 18 wheeler. I'm in the truck for 3 weeks at a time, then home for a few days. trying to drive a 5 speed always jacks me up, being so accustomed to the 13 speed. it's nice to not even think about what gear I need to be in, just drop the top and go!
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Old 06-08-2010, 02:40 PM   #27
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...I really didnt mean to hit a nerve there..
Ya didn't hit a nerve. We are just trying to let you know that you don't know what you're talking about.
I too first thought a manual would be better for off-roading, that is until I used one off-road.
Now I know better and don't pretend to know something I don't know anything about!
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Old 06-08-2010, 02:43 PM   #28
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So either way, re-gearing is optimum? If I go 32's, no need? And with my DD, I just couldn't do 5 speed, too much work!
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Old 06-08-2010, 02:53 PM   #29
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Whenever you install larger tires, gearing that was optimal before is no longer optimal. At certain tire size boost points, it becomes time to regear. Most consider the 33" tire size the size tire at which they get serious about regearing the axles to a lower more optimal ratio.
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Old 06-08-2010, 03:02 PM   #30
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Thanks Jerry, I value the opinion of those way more experience than me. Is re-gearing a job for a moderate mechanic? I can align a leg, but haven't tried tearing into a vehicle yet.

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