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Limited Slip Differential vs. Posi-Traction

mgroeger

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The other day I turned off traction control and did a burn out and I noticed I had to sets of tire marks left on the road. I don't have a LSD so I was wondering how this was possible. I remember on old RWD cars that some had posi-traction. Do Jeeps?
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Jeepsterfreak

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The other day I turned off traction control and did a burn out and I noticed I had to sets of tire marks left on the road. I don't have a LSD so I was wondering how this was possible. I remember on old RWD cars that some had posi-traction. Do Jeeps?
If you have a Sahara and don't have the LSD, then you have an open diff.
 
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mgroeger

mgroeger

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Yes, I am aware of that. I am trying to understand why I laid two patches of rubber down, which means both wheels were engaged.
 

Jeepsk8

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Posi-traction is a brand name of an LSD (I believe Eaton). Keep in mind that Jeeps have brake lock differential (BLD) function where the computer senses a loss of traction in one wheel and lightly applies brake to the wheel that is spinning to split the power to the other wheel. This is an old driving trick taught in offroad classes, you can actually do this yourself by two footing it.
 
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mgroeger

mgroeger

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Hmmm... I had the traction control turned off and my foot off the brake so how could the computer tell? Also regarding the old school trick, how exactly does that work? You gently apply the brake why hitting the gas?
 

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BLD is always ON even with traction control off. Locked diff is the only case where it is off
 

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Open diffs can still spin both tires, you just do not have any assurance that it will happen since it there is nothing forcing both tires to spin.
 

Jeepsk8

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Hmmm... I had the traction control turned off and my foot off the brake so how could the computer tell? Also regarding the old school trick, how exactly does that work? You gently apply the brake why hitting the gas?
Well, yes, but it is used in an off-road application where you are maybe trying to climb a rock garden and your tires begin to slip, lightly applying the brake will split the power to the other wheel and hopefully get you over the obstacle. I don't think it's as effective in a burnout necessarily but in theory it should work. The computer uses the wheel speed sensors to detect when one wheel is spinning and applies a little brake the same way, that is how a BLD works.
 
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mgroeger

mgroeger

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OK, I understand. I didn't do a line lock or anything like that. I simply turned traction control off and punched it. It was fun :)
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