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Old 05-09-2014, 12:57 AM   #1
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Gear ratio

Currently have dana 44 rear and hp 30 front 4.56 gears with the 2.5l automatic on 33's. The motor was freshly built top to bottom and runs perfect but this thing is still slowwwww. Whats the best gear ratio to get it back to running stock if not a tab bit better? Willing to swap out the 30 for a 44 to get lower gears. Ideas??

Thanks!

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Old 05-09-2014, 09:17 AM   #2
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More info. What do you mean by slow? Highway slow? Trail slow? Those 4:56 gears are pretty low and if you want fast 4:10's might be a better option.

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Old 05-09-2014, 09:26 AM   #3
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Yea, axles are not your problem, it's your 4cyl & gears. As previous poster said 4.10's would probably help.

It sound like your concerned with road speeds vs. trail gearing?
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Old 05-09-2014, 11:27 AM   #4
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Trail gearing its fine its more the around town gearing. I stay off the highway anymore so thats not a factor. Its the hills around here going up a hill its peg to the floor and struggling to keep 30mph at times it actually starts dropping mph lol
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Old 05-09-2014, 01:00 PM   #5
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Quote:
Originally Posted by screwystewy View Post
Trail gearing its fine its more the around town gearing. I stay off the highway anymore so thats not a factor. Its the hills around here going up a hill its peg to the floor and struggling to keep 30mph at times it actually starts dropping mph lol
Sounds like you may have some other problems. How did it run before the rebuild? Is the exhaust stock (ie, is the cat still in place)? Brake calipers stuck? Your Jeep looks heavily modded, have you added a lot of weight?

I ran some rough numbers. Most of the 2.5s had 225/75-15s and 3.73 gears with the 3 speed auto although I've driven a few and felt like they should have had 4.10s from the factory. The 225/75 is theoretically a 28" tire so the 4.56 gears with 33s should have put you to slightly better than stock but wouldn't allow for extra drag or weight gain. You can go up to 4.88 in the D30 HP, would be about a 7% increase over the 4.56s but probably not worth the cost to regear unless you do it yourself. Since you aren't doing any high speed driving, even 5.38s might work, would put you at about 3065 rpm in drive at 55 but like you said, you would have to go to a D44 in the front. 60 to 65 mph would probably wide open for highway cruising (about 3500 to 3600 for extended periods).

If everything is good with the motor, I would start looking at ways to make it lose weight or start considering some sort of engine swap.
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Old 05-09-2014, 02:28 PM   #6
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One more thought, have you checked fuel pressure? I have seen a weak fuel pump cause low power issues on a 98 2.5 auto that belongs to a good friend of mine. The Jeep ran, just had no power under load.
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Old 05-10-2014, 12:11 AM   #7
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Thanks for the info! Motor ran fine before rebuild had a knock and turned out to be #4 cyl had a cracked piston and few other problems. Full rebuild of the engine and a brand new fuel pump and fuel filter. The jeep runs great but trying to pull a hill it just seems to run out of gear. The power is there but its to the floor and barley keeping up speed. Brakes are all new from lines to calipers but i did just swap in the rear 44 so I'm gonna check out the emergency brake and make sure its not dragging. Jeeps getting a new exhaust at the moment so ill check that out tomorrow and see.
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Old 05-10-2014, 09:09 PM   #8
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Sounds good, mainly making sure your exhaust wasn't plugged but also that the cat was in place so the 02s were giving bad signals to the ECM. One more thing, the cam could be retarded from the rebuild which would hurt the low end but would help the high end unless it's really bad off. Advancing the cam will help the bottom end but hurt the high end. Didn't know if the cam was set "straight up" or not. Also, I don't know how to set the initial advance on the distributor on the TJs but could be your ignition timing is retarded. I know the ECM will adjust and compensate but it needs to be in or at least near the right position.
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Old 05-12-2014, 01:53 AM   #9
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Got the jeep back from the exhaust shop and all was good for about the first 50 miles then cel came on. Came back to a code 43 cyl misfire. So now i gotta check that out. It never ends haha

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