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Old 10-20-2009, 08:12 PM
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downshifting on highway

when im going down the highway if i start going uphill it almost seems to downshift right away..i have a exhaust, intake, tuner and always am on the highway with a performance tune..could it be because i have a six inch liift with 37" tires and the stock gearing?
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Old 10-20-2009, 10:13 PM
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It's 100% your gears. 3.73 on 37" you will have all sorts of lugging and shifting problems. Even 35" would bug me. I put 4.56 gears in my truck but it wasn't cheap. My dads jeep ran 35" with 4.10s and it sucked until he put in 5.13s and now its snappier than my truck. Seen enough jeeps and trucks with these problems. I wouldn't run oversize tires on a vehicle unless I changed gears. Hard on the engine, terrible on the transmission and sucks for your checkbook with mpg.
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Old 10-20-2009, 10:19 PM
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Quote:
Originally Posted by metstroke06 View Post
It's 100% your gears. 3.73 on 37" you will have all sorts of lugging and shifting problems. Even 35" would bug me. I put 4.56 gears in my truck but it wasn't cheap. My dads jeep ran 35" with 4.10s and it sucked until he put in 5.13s and now its snappier than my truck. Seen enough jeeps and trucks with these problems. I wouldn't run oversize tires on a vehicle unless I changed gears. Hard on the engine, terrible on the transmission and sucks for your checkbook with mpg.
i second that its your gears and tires. custom tunes would help out a lot. the shift points will be way different. i i use to have TC lock up at 47mph. and with the custom tunes my 140hp locks at 53mph and my 80hp tow locks at 63. im running 38's
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Old 10-20-2009, 10:25 PM
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hmm thats kind of what i thought, what are we talking here?? 1500 out the door for front and rear? so these stock gears would be the reason my transmission is clunking every once in a while during dialy driving?

another question...next week im headin out on a 20 hour drive, think i would get better gas mileage if i quick ordered a custom tune? would that solve my problem for now? cause really downshifting on a hill you can see over, its so damn annoying..its like every little hill you come to you downshift like right away..it kind of gets me goin thinkin about it

Last edited by yosh30; 10-20-2009 at 10:32 PM.
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Old 10-21-2009, 12:13 PM
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you're lookin at minimum 2000 is say for gears alone. I got lockers and mag hytec covers so mine was like 3700. How long you been running 37" tires on ur stock gearing? The clunking you are hearing could be your torque converter locking. What tuner you use?
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Old 10-21-2009, 01:55 PM
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The truck has had the lift and 37 inch tires for about half its life(it has 69,000 on it now).. im running SCT x3 with canned tunes (running on performance tune)..looking to go to custom tunes though cause the shifting just makes me cringe sometimes..
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Old 10-21-2009, 02:36 PM
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I don't know about your transmission but my guess it is very unhappy right about now. Whether or not you've done permanent damage I don't know but I would recommend getting gears first then getting custom tunes which they will program your tire size and gear ratio. If you get custom tunes, they will program your stock gear ratio, than if you get gears, you will need to reprogram your gear size, which really isn't too difficult to do on your own if you wanted to get a custom SCT tunes first. If you want to prevent any further damage to your transmission I would start looking for some estimates on gears and order a SCT X3 with tunes by Eric. Good luck, any further questions feel free to ask.
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Old 10-21-2009, 02:37 PM
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If you make long trips and want the best MPG on 37" tires, I'd recommend 4.30 gears. If you wanted a little more pull you can over gear slightly to 4.56 and that gives you the option of getting larger tires in the future considering the expense.
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Old 10-21-2009, 03:05 PM
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called a couple places today, right around 2500 to do it on my truck..i was thinking 4.10's on my truck atleast thats what ive seen around this blog..really the only time i travel long distance is about 3-4 times a year which there and back is 1500 miles..what are 4.30's like in town? is it pretty much like going back to stock?

a little more info:
i dont really tow all that much, jet ski trailer in the summer, an occasional 21ft enclosed snowmobile trailer in the winter
most of my driving is in town 4-6,000/year
abut 2-4,000/year thousand miles are on interstate

Last edited by yosh30; 10-21-2009 at 03:35 PM.
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Old 10-21-2009, 04:14 PM
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4.10s? with 37" tires you will be under geared and that $2500 will be a waste of money then. Some superduty's come with 4.10 stock. With 37" tires, 4.30s will put you back to stock. 4.56 will be a lot better than 3.73s. I run 4.56's with 37" tire and I like it. Although 4.30s I would think would be ideal for you. 4.30's are typically a little more expensive than 4.56s because only gears that make 4.30s are like precision and they are expensive, but worth it. Please don't get 4.10s. Either 4.30s or 4.56 are my recommendation. Find yourself a gear/tire chart.
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