Limited slip and locking differentials
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==Introduction== | ==Introduction== | ||
| − | A limited slip differential (or "diff") is a means to apply power to the ground when traction is limited, by sensing which wheel has traction and applying force to it, while maintaining the wheel speeds to be different when turning instead of only to the wheel that is without traction like how an open diff works. | + | A limited slip (or "posi") differential (or "diff") is a means to apply power to the ground when traction is limited, by sensing which wheel has traction and applying force to it, while maintaining the wheel speeds to be different when turning instead of only to the wheel that is without traction like how an open diff works. |
==How to tell an open differential from a limited slip differential (LSD)== | ==How to tell an open differential from a limited slip differential (LSD)== | ||
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In some isolated cases like the second generation Pontiac Trans Am, a 10-bolt 8.5" corporate LSD rearend was standard equipment, so they will have a LSD if it's original (except cars specifically ordered with an open rearend). | In some isolated cases like the second generation Pontiac Trans Am, a 10-bolt 8.5" corporate LSD rearend was standard equipment, so they will have a LSD if it's original (except cars specifically ordered with an open rearend). | ||
| − | So, checking whether a differential is limited slip or not isn't as simple as jacking up the rear of the car and turning the wheels, or seeing if both wheels spin when you hammer it. The only way to be 100% certain of what type of differential is in the rearend is to remove the cover | + | So, checking whether a differential is limited slip or not isn't as simple as jacking up the rear of the car and turning the wheels, or seeing if both wheels spin when you hammer it. The only way to be 100% certain of what type of differential is in the rearend is to remove the cover or drop the center section and look to see what's inside. |
{| | {| | ||
| − | |[[File:Open diff.jpg|thumb | + | |[[File:Open diff.jpg|thumb|300px|center|Open differential]] |
| − | |[[File:Auburn limited slip differential.jpg|thumb | + | |[[File:Auburn limited slip differential.jpg|thumb|300px|center|Auburn limited slip differential]] |
|} | |} | ||
{| | {| | ||
| − | |[[File:Cutaway lsd clutchtype.jpg|thumb | + | |[[File:Cutaway lsd clutchtype.jpg|thumb|300px|center|Cutaway of a clutch-type LSD]] |
| − | |[[File:Limited slip diff cone.jpg|thumb | + | |[[File:Limited slip diff cone.jpg|thumb|350px|center|Cutaway of a [http://en.wikipedia.org/wiki/Limited-slip_differential cone-type] LSD]] |
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Depending on the type and application, there may be some slip allowed, i.e. the two wheels are not connected to one another directly, like in the case of the viscous, clutch, and cone types. In other cases (like the locking-type differentials), the wheels are directly linked while in the locked position. | Depending on the type and application, there may be some slip allowed, i.e. the two wheels are not connected to one another directly, like in the case of the viscous, clutch, and cone types. In other cases (like the locking-type differentials), the wheels are directly linked while in the locked position. | ||
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| + | ==Lockers== | ||
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| + | {| | ||
| + | |[[File:Detroit locker.jpg|thumb|550px|center|[http://www.eaton.com/Eaton/ProductsServices/ProductsbyCategory/Automotive/AutomotiveAftermarket/Differentials/PCT_221432 Eaton Detroit locker]]] | ||
| + | |[[File:ARB air locker.jpg|thumb|350px|center|[http://store.arbusa.com/Air-Lockers-C7.aspx ARB Air Locker]]] | ||
| + | |} | ||
| + | {| | ||
| + | |[[File:Eaton elocker.jpg|thumb|450px|center|[http://www.eaton.com/Eaton/ProductsServices/ProductsbyCategory/Automotive/AutomotiveAftermarket/Differentials/PCT_339903 Eaton ELocker]]] | ||
| + | |[[File:Auburn ected max.jpg|thumb|310px|left|[http://www.auburngear.com/aftermarket/product_listing.aspx?category=8946f7ff-e4b5-4b07-b738-c6f9d7f93179ARB Auburn Ected Max]]] | ||
| + | |} | ||
==="Lunchbox" locker=== | ==="Lunchbox" locker=== | ||
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The lunchbox locker, or "drop-in" locker is a type of automatic locker that replaces the side (axle) gears and spider (pinion) gears (in some/most types) of a diff. The pinion gears referred to here are NOT the same as the pinion gear that meshes with the ring gear. Instead, they're the smaller gears in the center of the diff that allows the two wheels to rotate at different speeds when turning, etc. | The lunchbox locker, or "drop-in" locker is a type of automatic locker that replaces the side (axle) gears and spider (pinion) gears (in some/most types) of a diff. The pinion gears referred to here are NOT the same as the pinion gear that meshes with the ring gear. Instead, they're the smaller gears in the center of the diff that allows the two wheels to rotate at different speeds when turning, etc. | ||
| − | A lunchbox locker is relatively easy to install, mainly because the original backlash and preload settings are not disturbed during the installation. The lunchbox locker will only be as strong as the original carrier and rearend housing it's installed in, so using one in a weak design will ''still'' be a weak design. One thing that makes it better than some of the less expensive alternatives to a proper LSD is the lunchbox does act as a differential. Not particularly well, though, and because of its idiosyncrasies its generally not recommended for street use because of things like how it can lock while cornering, depending on how the power is applied. | + | A lunchbox locker is relatively easy to install, mainly because the original backlash and preload settings are not disturbed during the installation. The lunchbox locker will only be as strong as the original carrier and rearend housing it's installed in, so using one in a weak design will ''still'' be a weak design. One thing that makes it better than some of the less expensive alternatives to a proper LSD is the lunchbox does act as a differential. Not particularly well, though, and because of its idiosyncrasies its generally not recommended for street use because of things like how it can lock while cornering, depending on how the power is applied. More [http://www.offroaders.com/tech/Lunchbox-lockers.htm here]. |
| + | [[File:Auto locker.jpg|thumb|160px|left|Lunchbox locker]] <br style="clear:both"/> | ||
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===Spools=== | ===Spools=== | ||
| − | A spool is not a differential, and isn't considered to be limited slip, either. A spool connects both wheels the same as if there were a live axle (think of a go kart from the '60s). In the case of a spool | + | A spool is not a differential, and isn't considered to be limited slip, either. A spool connects both wheels the same as if there were a live axle (think of a go kart from the '60s). In the case of a spool, mini spool, or welded spider gears, both wheels are turning the same speed all the time- even when going around a corner or doing parking lot maneuvers. This causes the inside wheel to rotate faster than it needs to when cornering or maneuvering. The result is reduced tread life, squealing of the tires even at slow speeds when turning, and a lot of stress on the rear end components. Not to mention a potential loss of control in low-traction conditions like ice, snow or rain. |
| − | A mini spool is much like a spool, but without the strength of a spool because like the lunchbox locker, it only replaces the spider and axle gears; the rest of the rear end is all reused | + | A mini spool is much like a spool, but without the strength of a spool because like the lunchbox locker, it only replaces the spider and axle gears; the rest of the existing rear end is all reused. |
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|[[File:Mini spool.jpg|thumb|245px|center|Mini spool]] | |[[File:Mini spool.jpg|thumb|245px|center|Mini spool]] | ||
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===Welded spider gears=== | ===Welded spider gears=== | ||
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A welded diff has the dubious distinction of not only having all the drawbacks of a spool on the street, but also adds the danger of loss of control should the welds break and jam between the ring gear and pinion- which will lock the rear wheels. Not what you want to happen at ANY speed, let alone at the top end of a run, or while carving the canyons. | A welded diff has the dubious distinction of not only having all the drawbacks of a spool on the street, but also adds the danger of loss of control should the welds break and jam between the ring gear and pinion- which will lock the rear wheels. Not what you want to happen at ANY speed, let alone at the top end of a run, or while carving the canyons. | ||
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| − | {{warning|The | + | [[File:Welded spiders.jpg|thumb|250px|left|This is what an open diff with welded spider gears looks like]]<br style="clear:both"/> |
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| + | {{warning|The reason the spools and welded diff are shown here is so they can be identified if they're found inside a rearend. It should be stressed that the street is no place for a spool or welded spiders. Period. It matters very little to anyone who finds themselves upside down in a ditch that someone ''else'' claimed they drove on the street for 20 years with one of these without any problems. What '''should''' matter is that using either one on the street is a very unsafe practice that should be avoided altogether. A spool is a racing modification only. A welded diff is not safe on the street OR track. '''''Just don't do it'''''.}} | ||
==Resources== | ==Resources== | ||
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