i want to put lower gears in my 86 F250 it has a 460 with dana 60's a c6 and an np205 T-case i am runing a set of 33x14-16 boggers i think the truck has 4.10 in it i also want to add lockers

 

My 85 F-250 is in the shop right now getting 4:10 gears installed. I am running 285/75R16 tires which I believe is about 32-33" tall. It had 3:55 gears, but I want more grunt for pulling. You may want to see what gears you have, I have the exact same drivetrain as you, and before my tire change was running 3k rpm's at 75mph. After the tire change, it went to 2800 rpm's. I am thinking the gears will take it to around 3200-3500 rpm's. If you have 3:55's like me I have been told that 4:10's with a 33" tire is a good setup, but if thats not enough, you could go with some 4:56 gears.

 

Well the first question is what will the truck be used for? If you plan on doing a lot of heavy towing and off roading with it and going no bigger than 35s, I would stick with the 4.10s. As for lockers, I would only use one in the the rear and go with a limited slip for the front. You want the front to have some give or you won't be able to turn when you're locked in 4wd. I would recommend a Detroit Locker for the rear, you have a big heavy truck with a lot of torque; so you'll want something strong enough to stand up to that big ol 460. For the front I would use an O.E. style or a step up limited slip unit, I have heard nothing but good about the Dana/ Spicer Trak Lok and Powr Lok units. You can find both at BroncoGraveyard.com. The Trac Lok is the same unit Ford used at the factory, it is highly recommended for front applications on most 4x4s. The Powr Lok is said to be the strongest clutch type limited slip unit on the market, it has 90-95% lock up capability, it is not recommended for front applications on street driven vehicles. My own work in progress: 84 F150 reg cab long box, mildly built 300 six, 4 speed grannybox, 2.5 inch suspension lift, 31s, 3.08s-locked rear. I am currently running the stock 3.08 gears (hate em) with 31x10.5 Ironman All Terrains. This past July I installed a Rough Country 2.5 inch suspension lift and a Powertrax No-Slip locker in the rear. This past fall I added EFI manifolds, dual exhaust, and a Holley 2bbl carb. I couldn't be more happy with the recent mods. My future plans include: 4.10 gears, Dana/ Spicer Trak Lok in the front, 33 inch mudders, and maybe a 2 or 3 inch body lift.