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post #1 of (permalink) Old 02-08-2010, 12:13 PM Thread Starter
 
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Need Tj advice.

I have a 97 jeep tj se with 3 inch body and 31's. So basically stock. Im gonna get a rubicon express lift and plan on putting 35's or 37's on. Problem is i have the 2.5l and want to know if theres any way i can turn 37's with the 4 cyl..and dont tell me to get a 4.0 cuz i only have 1000 miles ona new block
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post #2 of (permalink) Old 02-08-2010, 01:14 PM
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I'd say you will need lower gears and a stronger rear, depending on what you want to do with your Jeep.

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post #3 of (permalink) Old 02-08-2010, 01:46 PM
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and dont tell me to get a 4.0 cuz i only have 1000 miles ona new block
Ok, I won't....

Anything else you don't want anyone to tell ya?
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post #4 of (permalink) Old 02-08-2010, 02:40 PM
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I agree with the stronger axles and lower gears. With the 4 cyl. you'll want at least 4.88 gears but would like 5.13's better. If you plan to take it off-road anything you put into the D35 rearend is just wasted money.
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post #5 of (permalink) Old 02-08-2010, 02:44 PM
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Quote:
If you plan to take it off-road anything you put into the D35 rearend is just wasted money.
I'd say the same about the D30 front, but I'm probably in the minority.

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post #6 of (permalink) Old 02-08-2010, 04:11 PM
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Originally Posted by Jim_Lou View Post
I'd say the same about the D30 front, but I'm probably in the minority.
Wouldn't be able to put 5.13s in the D30 anyway. and 37s on a D30.. Eh imo i'd ditch the 30 too

1990 YJ 258 l6 3.5 BDS lift

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post #7 of (permalink) Old 02-08-2010, 05:53 PM
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Learning proper English instead of textz English might help.

All joking aside. It's possible to run 35's or 37's but it isn't as simple as bolting on a lift kit.

First Question, what do you want to do with the jeep? If it's just pick up whores at the mall and cruise main street either learn to slip your clutch or drive around in low range and have a top speed of about 45 mph.

Ok now some real information. Everything I'm going to type here on out is geared towards running moderate trails, if you want to run crazy stuff like the hammers get some experience before you make any decisions.

Your factory axles in stock form will not like 35" tires for much more then cruising the strip and even then your factory rear axle will not be happy.

Your rear is a dana 35, even if you put a super 35 or other turd polishing kit in it they still are boat anchors with small ring and pinion/ carriers. Your best bet is to swap it out for either a dana 44 that was optional in some 4.0 tj's (it bolts right in), an explorer 8.8 swap (do some searching, it requires some welding by you or some one else), or an even stronger axle either from the junk yard with some fab work or from an aftermarket company. A dana 44 is ok for 37 inch tires, an 8.8 is good for 37's and a dana 60 or ford 9" rear will also be good for 37's

Your front axle is a dana 30, it is in the ok to marginal category for 35's and pushing it 37's. Some people can make it live in stock form for ever with 37's, others look at it funny and it breaks. The 2 main weak points are the small ring and pinion/ carrier and the shafts/ joints. You can upgrade to axle shafts to aftermarket alloy shafts and u-joints but the ring and pinion will always be small. You can look into upgrading it or swapping in a dana 44 from a rubicon, or a junk yard/ aftermarket dana 44 or dana 60.

To gain your power back you need to swap your ring and pinion, 4.88's are the lowest gears that will fit in a dana 30/35. This will give you close to stock acceleration characteristics.

Off road you may still want more gear, you can either go with lower gears if you swap out your stock axles or look into lower gearing options for your transmission or transfer case.

If it's mainly a mall crawler/ very mild wheeler I would swap in a set of 4.88 gears (about $500 in parts and $500-$1500 in labor if you don't install them your self) and cross your fingers the dana 35 doesn't explode or swap in a factory dana 44 rear. If you run more than mild trails save your pennies for an axle swap/ gears before you invest too much money into factory axles.
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post #8 of (permalink) Old 02-08-2010, 06:31 PM
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Well, I would say a 4.0 would be nicer then the 2.5, but the 2.5 can be made to work. The 2.5's actually make rather good power for there size, more then the old 258. What they lack is torque, so you will need more gear reduction.

A lot depends on what you plan to do with the Jeep I am not familiar with your area of the country so I do not know what is available as far as trails. In general for mud you do not need as much strength in components but you do need more power, perhaps more then the 2.5 can make. If you want mud performance then you will likely not be able to get 37's turning very fast with the 2.5 so the tires will not clean out very well. Try to find a mud tire with a lot of room between the lugs (interco Boggers, or super swampers for example) as these clean better.

If you plan to do a lot of rocks then very little power is generally needed. It is more about gear reduction and throttle control. However, you will need more in the way of strength in axles and transfer case.

The 2.5 came with 4.10 gears from the factory with about 30 tires. So to keep the same final drive ratio with 37's you would need about 5.13 gears. I do not know if 5.13's are available for the Dana 35 or Dana 30. However, I personally would not use them even if they are. The Dana 35 and 30 already have small pinions and 5.13's will make them even smaller, reducing tooth contact and strength.

If you only plan to do mud and keep a light right foot I would say the Dana 30 may do okay. I would replace the Dana 35 with a Ford 8.8 or better axle though. For rocks I would upgrade both axles, the sky is kind of the limit there and again a lot depends on how much you like the skinny petal.

You do not say if you have an auto or manual gear box. Since autos where less common in the 2.5 I will assume a manual.

For gearing I would be inclined to keep what ever axles you use in the neighborhood of 4.10 or 4.56 gears, and get more reduction with a different gear box.

Consider the fallowing:
With a stock AX-5 manual with 0.85 overdrive and stock 4.10 axle gears, you have a high gear of 4.10 * 0.85 = 3.49. If we adjust from 30 to 37 inch tire and want to keep the same high gear ratio. 3.49 * 37 / 30 = 4.30 or very close to 4.56 if not over drive is used. Since the Jeep will have more air resistance it is better to round up on the gear ratio. So by swapping out gear boxes with a heavy duty 4 speed (a NP 435 for example) without over drive you can use 4.56 gears and still turn about the same RPM's on the high way. So

Looking at the lower end things are better then a AX-5 . With the AX-5 with a first gear of 3.93 and NP 231 transfer case with a low range of 2.72 and 5.13 axle gears you would have a crawl ratio of 55. However, with a NP 435 truck 4 speed (6.68 first gear) and 4.56 axle gears you get the same effective high gear, but get a crawl ratio of 83. The down side is that you have less gears in between and it will not shift as nice but you gain strength and crawl ratio with the same highway gearing.

I know you most likely do not want to redesign the whole Jeep for bigger tires but that is unavoidable. You are taking a designed for 30 inch tires and increasing the load on all components by about 25%. There is simply know way out of beefing everything up to compensate if you want parts to last.

Also consider the 3" body lift. This puts a lot more load on the bolts into the body and they have been known to rip out. Most folks feel that anything over a 1" body lift is just trouble waiting to happen.

Wilhelm

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post #9 of (permalink) Old 02-08-2010, 11:21 PM Thread Starter
 
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Ok im not totally Ignorant i know i will need to gear down, i already have a dana 44 front end and excuse my typing im on my iphone so sometimes it doeasnt come out like i intend. I have recently helped/observedy friends dad put in a four link rear suspension and rebuild the whole rear end, i have seen how much work it takes and taken part in it.. If you arent familiar with my area of the country, i live in northern californi and our laws suck, im about 1 hour 15 minutes from the snow, and 1 hour 30 min from the rubicon trail. I have conquered the snow all i need now is to go for the rubicon. My jeep will be primarily a daily driver, but i still want it to have
crawling capabilities, which is why i dont really want to go over 35's. I will have plenty of experienced people to help me so dont worry about that. My priorities are most of all Find a strong rear end, lockers, gears then lift it and get tires.
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post #10 of (permalink) Old 02-09-2010, 08:44 AM
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Quote:
I will have plenty of experienced people to help me so dont worry about that. My priorities are most of all Find a strong rear end, lockers, gears then lift it and get tires.
What you are considering is trying to make a slik purse out of a pigs ear because you've got a fairly fresh engine. You're going to be pouring a lot of money into a Jeep that really won't do what you want it to do. By the time you're done you've made a Jeep with mechanical fuses in it... those fuses are:
  • The transmission,
  • the Transfere case,
  • the Driveshafts,
  • the U-Joints,
  • the Yokes...
  • and the list could go on
  • and on.
IMHO, it may be better to sit down with all your experienced people and consider what you're going to do. They're not spending your money, you are... and you want the best bang for the buck.

I'd suggest that you simply keep the Jeep as it is, with the fresh engine installed and sell it. Then take the money you get from the Jeep and dump it into a different, more powerful platform for your build.

You'll be dollars ahead, have less headaches, less parts costs, less breakdown costs, and better fuel efficiency. That fresh engine may not be manna from heaven. It could be a milestone around your neck depending on the route you take. This could be a case of saving a penny and being pound foolish.

Think about what you're going to do, plan, plan, plan, then reconsider and plan some more before you act and commit. This is just a friendly warning that you are getting on an expensive treadmill you may not like; and it's hard to get off. There is no such thing as a cheap lift. Every lift has consequences, and your plan is no different.
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