Gears
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Senior User
Joined: Feb 2003
Posts: 395
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From: South Carolina
Gears
Just curious... a lot of folks seem to be doing 390 buildups anywhere from mild to wild. What size rear end gears are you guys running? And which type of locker works the best?
Lead Driver
Joined: Apr 2001
Posts: 6,175
Likes: 21
From: Texas
Gears
I'm running 4.10s with 255/70r16 tires. It is humming at about 3400 RPM at highway speeds.
If I get a locker it will probably be an ARB air locker. I like the on/off capability. I realize they are pricey, but if I'm going to pay somebody to install it I might as well get what I want. As I undersand it, gear and locker installation is best left to the pros.
I believe Detroit or one of the other makes has an E-Locker , Electronically activated locker. That may also be tempting if cheaper than the ARB. The ARBs reputation is pretty strong.
If I get a locker it will probably be an ARB air locker. I like the on/off capability. I realize they are pricey, but if I'm going to pay somebody to install it I might as well get what I want. As I undersand it, gear and locker installation is best left to the pros.
I believe Detroit or one of the other makes has an E-Locker , Electronically activated locker. That may also be tempting if cheaper than the ARB. The ARBs reputation is pretty strong.
Elder User
Joined: Feb 2002
Posts: 542
Likes: 0
From: Middleton, WI
Gears
Part of my re-do was switching rear to Auburn Limited Slip, upgrade to 31 spline axles, and going to 3.55 rear (from stock 3.25). Rear tires are 275/60/17, but still can't hardly take off without burning them. I put in a Lentech prepped AOD behind my 390, so I'm hoping that having a .67 final drive will help MPG with 3.55, it was 8-10 MPG before. All this is "Brand New" so have no road test report at present - but soon, very soon! 
Post Fiend
Joined: Feb 2001
Posts: 6,624
Likes: 8
From: Missouri
Gears
I run 3.70 gears with a mini spool. I got the whole third member for 50 bucks and put a 30 dollar mini spool in it. I like it but I want to get a full spool, 31 spline aftermarket axles and 4.56 gears.
Senior User
Joined: Jan 2003
Posts: 451
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From: Balfour
Gears
3.54's w/ 390 4v and np435, good for hauling but down the highway,hauling heavy stuff means going back and fourth between 3rd and 4th in hilly areas.good mileage
390 2v w/t-18 and 4.10's lots of low end power, not the greatest highway gears as far as mileage goes, but hauling heavy stuff and passing is a breeze.
I think 3.73's would be a good balence.. my o2
390 2v w/t-18 and 4.10's lots of low end power, not the greatest highway gears as far as mileage goes, but hauling heavy stuff and passing is a breeze.
I think 3.73's would be a good balence.. my o2
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1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
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