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Posted: Tue Jul 13, 2010 2:11 am
by charger440neon2.0l
I'm going to chime in here since i make several lsd's for different applications using the s-spring.

This is my limited slip tutorial

First of all I want the definition of a limited slip differential known, it is a differential that limits the torque split between the two driven wheels, whether its by one pound of torque or 600 pounds of torque. Anything you do to limit the differential action make that a limited slip.

Secondly we are working on a dodge so quit throwing the word posi around that is chevys name for limited slip
Dana/spicer=trac-lok or powr-lok
Ford=i dont know all i ever see is trac-loks in them made by spicer/dana

Thirdly there is a common misconception that the spider gears dont separate in open and some limited slip type differentials, thats wrong all gears that have torque applied to them will try to separate. other wise you could throw out all the thrust washers out of your tranny and expect to be fine.

horsepower of the engine make no difference to the working of an lsd except for when you are overloading a part to its breaking point.
Torque does play a role, the more torque applied the pinion and side gears the more they separate and rub into the carrier creating more resistance to the splitting of torque going out to the axles.
I kinda enjoy seeing the tk-100 green upgrade springs for the pg that say they can handle up to 300 hp because the hp does not transfer through the springs nor does it really create a situation where the pg would be incapable of doing anything other than creating a preload. The upgrade springs are a good idea since they are stiffer and create more preload, its just that they wont be affected by horsepower.

there are four s-springs available to my knowledge the ranger 7.? (fits neon no machining), the mustang 8.8 up to 2003 and mustang 2003 and newer 8.8 (.100"-.150" has to be machined from the face of the pinion gears to fit with either spring) and the f-150 spring (too big no matter how you look at it)

With the simple introduction of the s-spring or the phantom grip you preload the side gears to the diff carrier but you only end up with two friction surfaces to create drag to limit slip. the friction is not increased by friction material its just simple metal to metal. this does not create a very effective limited slip but it is by definition a limited slip. expect to see break away torque at about 10-15 ft.lbs. and continual resistance at 5-10 foot lbs. if turning a corner you gas it expect the inside tire to light up, if on slick surfaces expect both tires to spin, but as a side note some open diffs will spin both on slick surfaces too. Take into account that a car launched at 7000 rpm with tires spinning will have a faster 60 foot time with the pg or s-spring then a car without simply because there is a small amount of resistance to the slip built into the differential and will even out the speed difference between the tires faster. Small I know but its there.

Now an s-spring or a phantom grip with the thrust washer behind the side gears coated with friction material like that found in automatic transmission clutches creates a preloaded clutch type lsd. this creates four friction surfaces but only two usable since the thrust washer is neither splined to the carrier or side gear. these will wear out quickly but increase effectiveness alot. I like these on fwd cars since it provides a good bit of effectiveness, its cheap, and has little effect on steering.

now a splined clutch disc to the side gear and a separator plate splined to the case creates added friction thats needed to overcome before the differential action is achieved. like a clutch type sure grip or trac-lok. the trac lok in my truck has three clutches on each side gear, When I first put it together it had 780 ft.lbs. of breakaway and 650 of continuous resistance.

Some lsds use a cone type like chevys posi and the later model sure-grip chrysler. these used a cone shaped clutch either splined to the axle or side gear, the cone is fit into an inverted cone in the carrier as the the cone digs in creating resistance as its turned some have helical grooves cut into them so the cone acts as a screw to create more resistance these commonly have very little breakaway torque but as slippage occurs they build resistance.

Then there are viscous lsds that use the shearing force of the fluid to create resistance. I have not studied these enough to go into detail on their workings and most are non rebuild-able so there is really no need but they are advertised to never wear out so that creates even less interest in studying how they work.

then there are gear type like the obx they are complex so if it works thats great if not dont ask me. I have installed two into neons and hate them on a street car, they produce chatter when turning on blacktop and alot of scrubbing on rocks, I had one time that I was parking on a wet blacktop parking lot and had under steer at like 5mph because the inner tire just didn't have the traction to reach the breakaway torque and scrubbed across and caused a full loss of traction in that tire. but if you see alot of track and its not your daily driver you dont have to drive in rain or snow then its one of the best out there for you.

It all comes down to how much limit do you need? My truck has an lsd in the rear and a yukon gear spartan locker up front with a 2wd dissconnect it almost don't turn in 4wd but it will get one front tire completely in the air and still keep going. My neon has a ford ranger 7.? s-spring and friction material added to the thrust washers, I feel it working in the snow because it scrubs the inner tire and turning is hampered, it works when on the street and I nail the throttle in a straight line, in a corner though I nail the throttle and the inner tire lights up. I cant think of anything else to ever need in my daily driver. My charger has a cone type suregrip it does great donuts and is smooth as can be when turning

Posted: Tue Jul 13, 2010 2:12 am
by charger440neon2.0l
I hope that informs everyone about lsds better than fighting over whether it works or dont


Posted: Thu Jul 15, 2010 8:44 am
by drifterz73
thanx for the info....