what gears
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Junior User
Joined: Jul 2004
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what gears
ok well a about two years ago i had 373 gears put in my 81 f-150 and it was fun for awhile when i did not have to drive so far to work but now i have a trans am to go fast in so i want to make my truck more like a crusin truck and to take my four wheeler out of town what gears do i need i was thinkin about 273 or something like that because i have a built 3 speed tranny and i really dont want to waist my money on a aod oh my rear end is a 9 inch but right now i can only go like 70-75 miles an hour at 4000rpm very bad gas mileage with my 351m and will that help my gas milage putting in high way gears sorry for so many questions thanks again trevor
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Joined: May 2004
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My 3.08 with 4OD turns 2000 rpm at 75 mph, so you have alot of improvement possible. Even with NOT being in OD it would turn 2900 rpm at 75, so the axle change could make a huge difference. If I had the 2.73 axle my calculation says it would turn 2600 rpm at 75.
Why are you driving 75? You should do some google research about what happens to mileage as speed goes up. My truck hasn't even SEEN 75!
Why are you driving 75? You should do some google research about what happens to mileage as speed goes up. My truck hasn't even SEEN 75!
Lead Driver
Joined: Dec 2002
Posts: 5,491
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From: Kuna ID
If your truck is only 2wd you might try getting taller tires on the back. That will bring your rpms down as well. You mentioned taking your 4 wheeler out, are you talking about a quad/ATV etc., or are you pulling a jeep on a flatbed? If you plan on pulling a trailer, I wouldn't go any lower than 3:55's which considering you have 3:73's wouldn't be worth the money spent on the swap. I have 4:10 gears, 32.6" tall tire's and a 3spd auto tranny. I run 3000rpms at 70mph. You must be running pretty small tires to turn 4g's at 70-75mph with 3:73's.
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yes it s only a two wheels drive i have 2001 18in lightning wheels with a 295/45/18 and yes im talkin about a quad/atv sometimes very rarely i pull my dads trailer would the gears be ok since i do not pull stuff that much?? and how much are gears and where do i find them i went to summit i cant seen to find the type of gears i want thanks again for the help
Lead Driver
Joined: Dec 2002
Posts: 5,491
Likes: 16
From: Kuna ID
I really wouldn't go any lower than 3:08. You city mileage may actually get worse, but it sounds like you are more worried about a freeway style commute to work. To find gears, I would check out catalogs, or local drivetrain shops. Being the 9" is such a popular axle, you may get lucky and find a shop that recently swapped gears in a 9" and will let you have the old econo gears for free or real cheap. It would be really cool if you could find and extra 9" 3rd member in the junkyard that has the gears you are looking for. Then you could just swap them out saving you the cost of installation. IF you wanted, you could hang on to your 3:73 3rd member in case you changed your mind later on or wanted to go to the track. 
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