![\"Nine-1\"](\"http:\/\/www.racingjunk.com\/news\/wp-content\/uploads\/2014\/12\/Nine-1.jpg\")
<\/a><\/p>\nThe Nine-inch Carrier (Differential)<\/b><\/p>\n
When it comes to the carrier for a 9-inch Ford, there are three basic options available:\u00a0 Spool, Posi-Traction and Locker, and of course a series of variants in each (we\u2019ll get to that in a bit).\u00a0 You can also get an open carrier, but honestly, this isn\u2019t really a performance choice, at least for anyone contemplating a drag race situation. Mark Williams notes:\u00a0 \u201cAn open carrier uses a set of gears to allow slip. The thing to remember with an open carrier is that torque is always equal between both wheels. This means that if one wheel is slipping, the other will only be able to apply as much torque as the slipping wheel.\u201d<\/p>\n
\u00a0<\/i>Williams goes on to state: \u201cA spool is single piece carrier and does not offer any compensation for different rotating speeds in the wheels. Because of additional stresses created by a spool, it is not a good idea to run stock-spline axles with a spool. Spools should be run in race only type applications and are not intended for use on the street.<\/p>\n
<\/p>\n \u201cLockers use a ratcheting technique in combination with a cam to ensure that both wheels are locked together. The locker will not allow the wheels to spin at different speeds as long as there is forward torque on both wheels. The unit allows the outer tire to ratchet while turning a large radius such as cornering.<\/p>\n \u201cTorque Sensing differentials use mechanical means to control slip. They are rated with a bias, such as 5:1, that rates the amount of torque the unit is capable of applying to the non-slipping wheel. For instance if you are spinning with 20 ft\/lbs of torque, the non-spinning wheel will be able to receive 100 ft\/lbs in a 5:1 ratio. In a case where there is no torque on the loose wheel, the differential will not apply torque (this is why they recommend off-roaders apply the brakes when they slip). With an adjustable bias you can tune the differential to your needs.<\/p>\n \u201cPosi-Traction is similar to an open carrier and uses a set of clutches to apply torque to both axles. The clutches are pre-loaded by springs and the separating action of the spider gears increase the pressure on the clutch discs. Different clutch materials can be used as well as different static pre-loads to change the amount of torque needed to make the wheels slip.\u201d<\/p>\n For a strip only combination, then your best bet is a spool.\u00a0 Williams manufactures both steel and aluminum spools. On the steel spool side, the 4140 steel forgings are CNC machined, and heat-treated using the same austemper process as axles (we discussed it in more detail several issues ago).\u00a0 During the machining process, the ring gear register and the bearing diameters are precision ground to ensure zero run out on the ring gear mount surface.\u00a0 The cross-section beneath the ring gear register is increased in order to prevent ring gear deflection.\u00a0 Lightweight steel spools incorporate lightening holes drilled through the hub of the spool as well as a profile milled ring gear flange.\u00a0 This reduces the weight by as much as 25% over the standard steel spool, and it doesn’t sacrifice strength.<\/p>\n<\/a><\/a>