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Discussion Starter · #1 ·
So here I am, driving down the road with the wife and we're talking about the truck. I say I wonder if it has an LSD, she says go over to the shoulder and see. So I pull over to the shoulder and stop, I dump the gas and look back and see 2 nice lines in the sand and stone. So here it is, I'm with my boy and he asks me to tear one up, I hold the brake dump the gas and as I begin to spin I let off the brake. One patch. WTF? So do I have an LSD or not?
 

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Unlikely. Here's the short course... an open differential only differentiates (allows one side to coast while the other side gets power) when one tire has greater traction than the other. With an open diff, the tire with the LEAST traction gets the power.

With a limited slip, as you apply power (generalizing for simplicity) the clutches tighten up and apply traction to both tires to a certain extent.

The easiest way to tell is jack up both tires and spin one. If you have an open diff, the other will spin in the opposite direction.

If you have mud/ice/sand put one tire on pavement and one tire on the slippery stuff. If you move without hesitation, you're sporting the limited slip.
 

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thats weird

i have a sport with 3.92 gear and lsd and ive try the one wheel on black ice and the other on asphalt

i floor it and it did go forward but not that fast and i could definately feel one wheel spin,...

whats wrong is my diff broke?
or its normal
 

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Discussion Starter · #5 ·
OK so with a NON LSD, I certainly would not have had 2 wheel spin on the gravel shoulder ?
I'm trying to get the build sheet online from Dodge but it's proving difficult for some reason. Am I correct in thinking there is someone here that can get this with the last 8 digits of my VIN ? Which of course would be; J9530792
 

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You absolutely would have a 2 tire spin in gravel... you have relatively equal amounts of traction. An open diff isn't 1 wheel drive... equal amounts of traction gives you equal balance between tires.

Its only when there's a difference between tires traction OR tire speed (think a corner when they're not moving at the same speed) will the open diff differentiate.
 

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you can take your VIN to the parts desk at the dealer and they will print you the data on your truck. I learned so much about my truck from that sheet. all the technical data is there including gear ratios and if your have LSD or not.
 

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Discussion Starter · #8 ·
Thanks guys, much appreciated. Will be seeing the dealer later today. Anxious to know if LSD and gear ratio.
 

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Discussion Starter · #10 ·
3.55 gear which I'm happy about, but no LSD which sucks. Oh well.

Sethmark, that page only works for American registered trucks, but thank you just the same.
 

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One thing to keep in mind with LSD. It's operation is only as good as the friction plates. Typically, Chrysler LSD's don't have real strong lockup. I've seem many Jeeps, in off road situations, that have LSD where when one wheel was in the air it simply spun. The wheel on the ground was not getting strong enough lockup, from the LSD, to move the Jeep forward.

I have an LSD. As stated earlier in this string the only real test of an LSD is to jack up the rear and spin one tire. My LSD will work for now. My future is likely to include a Detroit locker though. I've used Detroit's on several of my previous Jeeps. Their tough and reliable
 

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One great thing with the 3.55 gears is you will get better gas mileage. i have the 3.92 with LSD and my mileage is not as good because i tach about 250rpm more at 110km then my buddies truck. i have never got better then 16.5 mpg and that is driving the prairies at 105kph with a tonnoue cover and [email protected] drop in filter. I tow a camper so wanted the bigger gears but for day to day driving yours are great.
 

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I have a '12 Express with 3.55 gears and LSD according to the build sheet and broadcast sheet. The truck has the new style ZF 245mm rear axle with the drain plugs on the passenger side of the axle housing and no filler plug in the differential cover.

I tested the LSD by lifting the axle up so that both wheels were up and in neutral and rotated the left tire by hand and the right tire rotated in the opposite direction. Then I lowered the truck so that only the right tire was on the ground and I could spin the left tire that was off the ground. So I'm like hmmm what's up with this LSD.

Next I drive to a open asphalt parking lot to do a pavement test. I pressed off the ESP button and then poured water on the left tire and in front of it and the right tire was on dry pavement then nail it which spun both tires. Then I poured water on the right tire with the left tire on dry pavement and nail it and both tires spin. The I do a brake torque on dry pavement and both tire spin and finally I pour water on both tires and in front of them. Then cut the wheels to the left and nail it and do a 360 with both tires smoking.

So I'm confused about testing the LSD, it acted like a open differential with the tires off the ground but on pavement it behaves like a LSD with both tires spinning
even with unequal traction. This must be a torque sensing differential because it will act like a open differential until torque is applied then both wheels spin.

Anybody know what type of LSD they are using for the 245mm ZF axle?
 
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