Need to regear?
Tuned
Joined: Jul 2005
Posts: 353
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what gears do you have now? What size tires came on your truck? That size tires will most likely require a regear, but what ratio depends on what you got now and what you want outta your truck. Lower gears will give better off the line and towing performance at the expense of hwy mileage. It's all a compromise. But if you're lifting your truck and putting much larger tires on it than we can assume your main priority is not fuel mileage. If so 4.11 or 4.56 or so gears will give you better off the line performance, but will make your engine spin faster at hwy speeds and thus decrease mileage.
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Elder User
Joined: Mar 2004
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From: CT
The new tires are about 34.5" (315/25.4*.70+17). You old tires are problably in the 31" range. To maintain the same performance as a 3.55 gear your new gear should be 3.95. If you go with a 4.10 you will have slightly better accel, but you will turn slightly more RPMs(75) on the hwy. To maintain the same performance as a 3.73 gear you new gear sould be a 4.15. The impact now is just the opposite, slightly worse accel, but slightly less RPMs(25) on the hwy.
Either way I would go with the 4.10 unless you are going to be drag racing. If you go with the 4.56 the result is the same no matter what gear you currently have, vastly improved accel and way more RPMs (200-300)on the hwy depending on your original gear.
Either way I would go with the 4.10 unless you are going to be drag racing. If you go with the 4.56 the result is the same no matter what gear you currently have, vastly improved accel and way more RPMs (200-300)on the hwy depending on your original gear.
Last edited by ctfordguy; Jul 28, 2005 at 10:11 AM.
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New User
Joined: Jul 2005
Posts: 17
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Thanks alot for the info. I talked to the technician at 4wheelparts.com and he said to go with the 4.56 gears. I got my tires in today and had them mounted. Noticed a little difference in acceleration but not as much as expected.
Junior User
Joined: Jul 2005
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Your tires will be a lot harder to push they will be around 80 lbs each, if you change gears to 4.56 you will need to reprogram to get things right. I have the 5.4, 35's with 4.56 gears and like the power. I turn about 2200 rpms at 75 mph. I think if you go with the 4.10 you will wish you had the 200 rpm difference in power on the highway. I dont see a huge drop in MPG but need some more time to play. The 4.6 likes to wind up I think you will have a lot more fun with the power.
