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ok, this is a c&p from a post i made on a forum i used to be a member of, i've supplemented the previous info with videos from youtube, where applicable, to help people understand how the individual diffs work
so, i'm sure a lot of people are confused about what the differences are between different types of differentials... i know i have questions, so i figure it is time to start a thread that outlines the details and differences in them... and i'll edit this post to add in new information when people add it
Open Differentials: these are the basic differentials almost every rear wheel drive or 4x4 have, the differential puts power to which ever wheel has the least amount of traction, aka "one tire fire" on fords, it tends to be rear right tire. can be most easily identified by lifting the rear end, and spinning one tire, the other tire will turn in reverse of your direction, upside: cheap, can find them virtually anywhere. Downside: almost everything else, give the lowest possible traction in any situation where tires may spin
Limited Slip: AKA Posi, Positrac, Positraction, Positivetraction (all of which are GM terms for their brand of l/s) tracloc/traction lock (ford's brand) or anti spin (mopar) these usually use a series of clutches, that does not allow the 2 wheels to spin at different speeds, until there is a difference of a set amount of torque, on my mustang i believe it was 13lbs. upside: far superior traction over the open differential, as you have all drive wheels turning, so you will have double the traction. allows the wheels to spin at different speeds when driving on the road (for going around corners) downsides: clutches wear out, and eventually it will loose it's grab, and act like an open diff. not a full locker, and can cause 1 tire to not have power if the difference in traction between the wheels is great (ice on 1 tire, pavement on another)
the s shaped spring is designed to put pressure on the clutch disks
Torsen: this is by all definitions a limited slip differential, however uses series of gears to transfer power, the name is a brand name, from the Torsen Zexel corporation, torsen is taken from "torque sensing" also known as a torque bias differential, these differentials literally take torque away from the wheel that is spinning, and send it to the wheel with traction. There are limitations for the different types of torsens that exist. these are stock on the 2002-2007 Ford Ranger FX4 Level II's as well as a select number of ford mustangs.
Spool: quite possibly the best differential for racing or off roading, this diff uses no moving parts (spider gears, clutches, ect) so will not wear out, the only "consumable" parts are the ring and pinion gears, which will wear no more than on any other differential. this differential works as a solid unit between the 2 axle half shafts, and makes the 2 tires spin the EXACT same speed no matter what. Upsides: tires spin the exact same speeds, which will give you superior traction in all situations. there is no moving parts, so it will perform the same from day 1 till the day it completely breaks (which is unlikely) downsides: does not allow the diff to slip when turning, which causes you to have 1 tire that has a tendency to hop around corners, or slide around corners. when making turns, 1 tire is already at a loss of traction due to the previous downside, and if considerable power is added to the wheels, it has a higher likely hood of slipping out with the other wheel (as 1 tire is all that is gripping) causes a very high amount of stress on the axle shafts.
Lincoln Locker: very similar to the spool, in all of it's abilities and performances, although, it is a home made spool, made out of an open differential, by welding the spider gears together to not allow them to turn, and let 1 wheel spin. upsides: all of the same as the spool. Cheaper than a spool (not by a considerable amount) downsides: all of the same as the spool, plus has a larger likely hood of breaking, due to the parts weakening due to welding in the diff. if the weld were to break off, due to poor penetration, it causes slag to be in the fluid which works as an abrasive and can destroy meshing gears. Typically stock open differentials are not designed to handle the same torque put through the axles as an aftermarket spool, so is more susceptible to failure
Auto Locker: automatically locking locker, this type of differential automatically switches between functions of an open diff and a spool, based off of loss of traction, difference of wheel speed and force applied. The side effects are that sometimes the locker will lock unexpectedly, and cause traction issues. They do also often have a clicking noise around corners.
Selectable Locker: this type of differential functions as a 100% open differential until the driver activates a switch, which through several different processes will lock the differential solid, and will cause it to function as a spool,
other names:
open diff: one tire fire, standard diff,
limited slip: posi, positrac, positraction, positive traction, tracloc, traction lock, torsen, anti spin,
spool: spool
lincoln locker: welded diff, home made spool,
Auto Locker: lunchbox locker, Lockrite
please note that the above examples do not show exact specs for all diffs of that type, nor is it inclusive of all differential types.
so, i'm sure a lot of people are confused about what the differences are between different types of differentials... i know i have questions, so i figure it is time to start a thread that outlines the details and differences in them... and i'll edit this post to add in new information when people add it
Open Differentials: these are the basic differentials almost every rear wheel drive or 4x4 have, the differential puts power to which ever wheel has the least amount of traction, aka "one tire fire" on fords, it tends to be rear right tire. can be most easily identified by lifting the rear end, and spinning one tire, the other tire will turn in reverse of your direction, upside: cheap, can find them virtually anywhere. Downside: almost everything else, give the lowest possible traction in any situation where tires may spin
Limited Slip: AKA Posi, Positrac, Positraction, Positivetraction (all of which are GM terms for their brand of l/s) tracloc/traction lock (ford's brand) or anti spin (mopar) these usually use a series of clutches, that does not allow the 2 wheels to spin at different speeds, until there is a difference of a set amount of torque, on my mustang i believe it was 13lbs. upside: far superior traction over the open differential, as you have all drive wheels turning, so you will have double the traction. allows the wheels to spin at different speeds when driving on the road (for going around corners) downsides: clutches wear out, and eventually it will loose it's grab, and act like an open diff. not a full locker, and can cause 1 tire to not have power if the difference in traction between the wheels is great (ice on 1 tire, pavement on another)
the s shaped spring is designed to put pressure on the clutch disks
Torsen: this is by all definitions a limited slip differential, however uses series of gears to transfer power, the name is a brand name, from the Torsen Zexel corporation, torsen is taken from "torque sensing" also known as a torque bias differential, these differentials literally take torque away from the wheel that is spinning, and send it to the wheel with traction. There are limitations for the different types of torsens that exist. these are stock on the 2002-2007 Ford Ranger FX4 Level II's as well as a select number of ford mustangs.
Spool: quite possibly the best differential for racing or off roading, this diff uses no moving parts (spider gears, clutches, ect) so will not wear out, the only "consumable" parts are the ring and pinion gears, which will wear no more than on any other differential. this differential works as a solid unit between the 2 axle half shafts, and makes the 2 tires spin the EXACT same speed no matter what. Upsides: tires spin the exact same speeds, which will give you superior traction in all situations. there is no moving parts, so it will perform the same from day 1 till the day it completely breaks (which is unlikely) downsides: does not allow the diff to slip when turning, which causes you to have 1 tire that has a tendency to hop around corners, or slide around corners. when making turns, 1 tire is already at a loss of traction due to the previous downside, and if considerable power is added to the wheels, it has a higher likely hood of slipping out with the other wheel (as 1 tire is all that is gripping) causes a very high amount of stress on the axle shafts.
Lincoln Locker: very similar to the spool, in all of it's abilities and performances, although, it is a home made spool, made out of an open differential, by welding the spider gears together to not allow them to turn, and let 1 wheel spin. upsides: all of the same as the spool. Cheaper than a spool (not by a considerable amount) downsides: all of the same as the spool, plus has a larger likely hood of breaking, due to the parts weakening due to welding in the diff. if the weld were to break off, due to poor penetration, it causes slag to be in the fluid which works as an abrasive and can destroy meshing gears. Typically stock open differentials are not designed to handle the same torque put through the axles as an aftermarket spool, so is more susceptible to failure
Auto Locker: automatically locking locker, this type of differential automatically switches between functions of an open diff and a spool, based off of loss of traction, difference of wheel speed and force applied. The side effects are that sometimes the locker will lock unexpectedly, and cause traction issues. They do also often have a clicking noise around corners.
Selectable Locker: this type of differential functions as a 100% open differential until the driver activates a switch, which through several different processes will lock the differential solid, and will cause it to function as a spool,
other names:
open diff: one tire fire, standard diff,
limited slip: posi, positrac, positraction, positive traction, tracloc, traction lock, torsen, anti spin,
spool: spool
lincoln locker: welded diff, home made spool,
Auto Locker: lunchbox locker, Lockrite
please note that the above examples do not show exact specs for all diffs of that type, nor is it inclusive of all differential types.
Last edited:
Lol kidding, great thread Weez.
