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Old 10-02-2014, 08:42 PM   #1
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Gear ratio questions

My 03 rumbles down the road at 70 with an RPM of only 1800. I am assuming it has the 3.55 ratio gears. Since it's a 4x4, I am also assuming that the front is matched to the rear.

How can I verify my assumptions?

The next option is the 3.92 which seems to be a better fit for what I am after. I want a snappier response than I have now. On the freeway, my truck will really respond at higher speeds but it feels like there is a soft spot at medium speed. I have a lot of peddle before it really responds.

Any help is appreciated.

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Old 10-02-2014, 08:47 PM   #2
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IMHO it is almost of waste of money to only go up one step in gearing. If you have a 3:55 and you change to a 3:92 I don't think you will see much difference. I would go to a 4:10. It will be a little expensive the change gears however because you have to change front and rear also if you have a 4x4.
Jay
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Old 10-02-2014, 08:55 PM   #3
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To confirm your gear ratio. Jack the rear up. Mark the drive shaft with a
Line. Have someone help you spin rear wheels at same time with truck in neutral and count how many times the drive shaft spins with 1 full tire revolution.
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Old 10-02-2014, 09:07 PM   #4
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Quote:
Originally Posted by Pull Ya View Post
IMHO it is almost of waste of money to only go up one step in gearing. If you have a 3:55 and you change to a 3:92 I don't think you will see much difference. I would go to a 4:10. It will be a little expensive the change gears however because you have to change front and rear also if you have a 4x4.
Jay
What will I give up ( top speed, gas mileage) and what will I gain (performance,shift points, acceleration) by going to a 4.10?
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Old 10-02-2014, 10:39 PM   #5
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I think the biggest improvement you will see will be in acceleration. I think that the change in fuel mileage will be very small(if any) and there will probably be little change in your top end. If you went to 4:56 or a 4:88 or even a 5:12 you would see a drop in mileage and top end, but the change in acceleration would reallllly be noticeable. Your shift points would remain at the same rpm, however you would be shifting sooner because the acceleration would be faster. A lower gear ratio would be more useful in town and at the drag strip and for towing, whereas a higher gear would be better for strictly highway use. IMHO 4:56 gears and lower are really not very good for highway use although some use that ratio to make up for really large tires.
Jay
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Old 10-03-2014, 03:07 AM   #6
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My 03 it's a 4x4,
What size tires(height) are you running or plan on running?
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Old 10-03-2014, 07:44 AM   #7
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What size tires(height) are you running or plan on running?
Excellent question. I am currently running the stock 17's with a 265 70R17 with a height of 30".

I really like the look of the 20's, but if I were to change I would not run a low profile tire to stay at the 30" height. I would also not try and put oversized tires on as well. I would assume such a change would add height, but not a lot of additional weight?

An increase of 2" would be nice aesthetically, but I would not want to have to lift the suspension to be able to accommodate the change.

So all of those factors figure in to the equation.
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Old 10-03-2014, 10:54 AM   #8
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as for your gear ratio u can contact dodge and give them your vin and the can send you a data build sheet on your truck and it will tell u everything from your gear ratio, tranny, basically everything that was on the truck when it left the factory
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