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need help thinking about new gears.

mr.p

Well-Known Member
Joined
December 30, 2007
Messages
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City, State
Berkeley, CA
Year, Model & Trim Level
04 explorer
now help me out here; using this website

http://www.angelfire.com/fl/procrastination/rear.html


with 3.73 gears, 32.5" actual diameter tires, the website says the top speed at 6500rpm in overdrive will be 242mph...sounds way off, and with 1 as my ratio "4th"

it says 169mph roughly...


now im thinking about gearing to 4.56 right now on the freeway i do about 65-70 at "2200" rpm, hard to judge rpm as it seems the torque converter slips quite a bit when cruising. i drive around with o/d off 90% of the time and have no problems with crazy high rpms or anything.


But when floored on an open road the explorer doesnt have enough torque to pull past 100mph really in a "timely" manner.




SO, if i went for 4.56 or so gears, i would be (according to the site) shifting into second at 50ish mph (instead of 65+) WOT, shift into 2nd at 80ish and so on, so i might be more in the powerband in 3rd or 4th WOT around 100mph...



What im getting at is what will be the negative effects of taller gear performance wise if i NEVER get to use the last 2 gears in the transmission anyways as they are too tall?
 



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come on guys someone jump in here :)
 






Well, there'd be no negative effects with going to the shorter gears... I say do it. Your transmission will thank you as well.
 






First of all, you don't need to be concerned about 'top speed'. Aerodynamics and lack of power will dictate your top speed, not redlining the engine in overdrive :rolleyes:.

You need to look at a chart like:
http://www.4wheelonline.com/superlift_tiresize.htm

Your truck came from the factory with 3.73 gears and roughly 29" tires, which puts you at 2809 rpm (without overdrive) at 65 mph. That is in the sweet spot (black area of the chart) for power and mileage. To stay in that 'sweet spot' with 32" tires, you need to have 4.11s or 4.27s. From personal experience, I like more gear. I would definitely go slightly lower than their recommendations, which puts you at 4.56.

I ran 5.13's with 33's in my old X for a while and loved the pulling power. It wasn't too friendly on the interstate at that point though.
 






thank you sir, i was just using the redlining in overdrive to exhaggerate the fact that i will NEVER see that speed anyways so shortening it up could only help.


i just dont understand why 1st is so tall of a gear...i could see that 2nd is 1st in overdrive maybe thats it.
 






Just for information the gear ratios are all the same weather you have OD on or off, also the manual gear ratios are the same. The torque converter locks up even if OD is off. It will lock in 3rd and 4th and depending on the computer programing it may lock in 2nd also.
 






i understand the gear ratios are the same what im trying to accomplish is get to around 2800RPM in od at approximately 70mph. I think 4.88's might have to be the way to go.
 






4.88 sounds good to me. :)
 






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