weird.. hmmm LSD Question

[neoamd]

I was under the impression my car had an open diff but I did 2-3 burnouts last ngith just to make sure my mind wasnt playing tricks on me and there were always 2 darks line that matched.. am I smoking crack?

The car is a 97 Base Model, I have a J30 VLSD in my garage right now and will sell it if I have a vlsd already, lol DAMN IT!

Anyone? I have a buddy with a 95 Auto with an open diff and he has one tire fire..

Thanks

Josh

[Craving4Boost]

you do not need to burn out to check if you have LSD..lol that is like the hardway....just jack up your car and spin your tires...if they both spin the same way you have LSD..if one spins the other direction then you dont...or you can just look under the car and i heard theres a yellow sticker which means its LSD...

i think this is the correct directions i'm not sure

[Tx-Sx-FS]

I believe if its LSD..theres an orange sticker..but the tires if LSD should spin the opposite direction of each other...and if open only the one tire should spin. my 2 cents.

[Craving4Boost]

well there you go....i knew i had something mixed up

[onosqv]

but the tires if LSD should spin the opposite direction of each other...and if open only the one tire should spin. my 2 cents.

Ummm, I think Craving4Boost was right when he said they should spin the same way. I know I have open diff & my rear tires spin opposite of eachother when jacked up & I'm pretty sure this has been verified in other threads before.

Open diff spins opposite.

LSD, VLSD, welded open diff, should all spin the same way.

If only one tire spins, I think the diff is f****d.

Only the front tires will rotate independently of eachother.

[Craving4Boost]

does welding a open diff. make it become the same as a LSD? does it work?

[Redline240]

There's way too much confusion about that wheel spinning on jackstands, if she leaves too strips shes lsd...that simple...

[ossBASHA]

zerothread?id=74103

[Import_Ant]

does welding a open diff. make it become the same as a LSD? does it work?

no. welding the spider gears makes it a locked diff. LSD = Limited SLIP differential. if it's welded together there's no slip it is locked 100% of the time.

does it work? yes to some extent. you have to know what gears to weld together and you are going to bark your tires any time you are turning the car (since the axles cant rotate at different speeds) but other than that it works just fine.

[comablack783]

sorry to jack ur thread guy, is there anything easier or more definite then “if one wheels spins the opposite way its not lsd”, and the “look for the orange VLSD sticker above the fill hole”. I’ve looked numerous times at the junkyard for an lsd and cant find anything, and I'm in FL, tons of 240s at the upick. First off trying to find an orange sticker that’s been covered in years of dirt and oil and nasty black grease underneath a car is not the easiest thing in the world. Second every single diff I've spun spins the opposite way. I’ve spun tons of 240sx se’s diffs with power everything, sunroof, abs, etc.., numerous 1st generation 300z turbos, even spun a few bmw 325s diffs which are supposed to have LSD standard (so I’ve heard), and nothing, they all spin opposite from each other, its driving me nuts. I’ve also heard that if it has hicas it has LSD… wtf does hicas look like? Is there anyway of telling with just the vin #s? or just by looking at it.

[Import_Ant]

every single diff I've spun spins the opposite way. I’ve spun tons of 240sx se’s diffs with power everything, sunroof, abs, etc.., numerous 1st generation 300z turbos, even spun a few bmw 325s diffs which are supposed to have LSD standard (so I’ve heard), and nothing, they all spin opposite from each other

are the driveshafts connected on these vehicles? that can affect it as well but here goes:

all J30's have VLSD's if you get onefrom a 95+ you'll have to get the axles too (swap your diff cover and it will bolt right up)

source (scroll to bottom for model listings)

in the J30 diffs where people say to change the flanges you can change axles much simpler IMHO. only 1990+ 300zx diffs are VLSD. The NA diff has a gear ratio that is equal to the 240sx (4.083:1) while the twin turbo uses 3:61:1

other than removing the diff cover there really isnt another way of checking aside from what's been mentioned.

[C-Kwik]

All diffs spin in the opposite direction when the driveshaft is locked in place. What you want to do to test a diff is feel if there is any resistance between the 2 output shafts. If you have an automatic, put it into park. If it's a manual, put it in gear(engine off of course). Lift the rear end. Spin one wheel. You WILL see the other shaft spin the opposite direction. If you have an LSD, there will be resistance. If not, it will feel very easy to spin. By locking the driveshaft in place, you isolate all rotations so that it much work through the diff. With a clutch and Viscous LSD, it will be very clear when you feel that it is hard to turn the wheels. Doubtful you'll be testing for a Torsen diff, but these will not show signs of resistance using this test.

[Fenvy]

this is vlsd, you probbaly have no lsd

[crzycav86]

All diffs spin in the opposite direction when the driveshaft is locked in place. What you want to do to test a diff is feel if there is any resistance between the 2 output shafts. If you have an automatic, put it into park. If it's a manual, put it in gear(engine off of course). Lift the rear end. Spin one wheel. You WILL see the other shaft spin the opposite direction. If you have an LSD, there will be resistance. If not, it will feel very easy to spin. By locking the driveshaft in place, you isolate all rotations so that it much work through the diff. With a clutch and Viscous LSD, it will be very clear when you feel that it is hard to turn the wheels. Doubtful you'll be testing for a Torsen diff, but these will not show signs of resistance using this test.

YES! This is how you test it.... sheesh.

And 2 stripes doesn't necessarily mean lsd.

[comablack783]

C-kwik you just blew my mind, are you saying that all diffs spin opposite? That it Doesn’t matter if its LSD or open its going to spin opposite regardless, that the difference is resistance? I mean it makes sense that there would be resistance in the output shafts but arnt they supposed to spin in the same direction if you have LSD? Or VLSD? … ive felt tons of resistance in trying to turn em sometimes and always passed em up since its spinng opposite from each other…omfg…are you sure. Also I have never checked to see if it was in gear or not, ergh!... if this is true then someone needs to sticky this and correct all those install pages that say “if it spins in the same direction its lsd, if the wheels spin opposite then its an open diff”.

another question, my brother has a 300zx diff that hes installing in his 240z, I swear when we pulled it I saw them spinning in the same direction (maybe I imagined it..), lots of resistance, however once it was off the car and we got it home it spun opposite with resistance, but when the driveshaft is spun the output shafts turn in the same direction, is this LSD or Open?
Modified by comablack783 at 1:49 PM 7/15/2005

[crzycav86]

When the car is in gear, all differentials will spin in the opposite direction... lsd or open. That's just the nature of differentials.(if it's welded, it won't spin at all, or it will turn the motor and the wheels will spin in the same direction). An lsd's differential will have a lot of resistance when spinning. An open differential's wheel will be easy to turn.

If the car is out of gear, an lsd's wheels will spin in the same direction. An open differential's wheels may spin in the same direction, they may spin in the opposite direction, or one wheel won't spin at all. It all depends on how much the driveshaft spins.

I hope that clears some things up.

[crzycav86]

All you really have to do is think of what lsd's and open differentials do.

An lsd's job is to keep the wheels locked to a degree. If you don't feel any resistance when trying to turn the wheels at different speeds, then it's an lsd that isn't doing its job, or it's a plain open differential.

[naed240sx]

My s13 has an open diff and on launch, both tires spin at an equall speed, leave two identical marks... you just have to be on a level surface. A lsd wouldnt even help me for straight line, the wheels lock up fine, just when cornering, only 1 wheel spins. As long as load, tire pressures are the same, this should be true.

[C-Kwik]

If you search through LSD posts throughout NICO, you'll probably see me repeat this same thing over and over again. Unfortunantely, people don't always listen and continue to regurgitate poor information.

As far as the diff, consider that the internals of a VLSD look very similar to an open diff. It has the spider gears in the diff portion. The difference is that the VLSD has a coupling that essentially connects 2 opposite spider gears so thatit resists trying to turn. Since the spider gears naturally will always turn in opposite directions it will resist turning in opposite directions.

If you think about it, in any kind of diff, the wheels on each side have to turn the same direction, under most conditions as it is required in order the car to move. If they turned in opposite directions, you'ld have movements more akin to a tank. The diff portion itself actually turns in opposite directions, but the entire assembly still turns forward with the ring gear. The effect is that the car actually sees one wheel going slower than the other in a turn, which is precisely the reason a diff is needed in the first place. What locking the diff in place does is isolate the movements inside the diff housing to the diff itself.

In most cases both wheels turning the same direction is a test that can work, but the results are not absolute. With a pinion/ring gear ratio of about 4:1, the likeliness of spinning a single wheel to overcome the resistance in the drivetrain and actually turn the driveshaft along with the other wheel in the same direction at the same speed is not very great. Just like how torque has a tendency to travel to the wheel with the least resistance in an open diff, it will take the path of least resistance and spin the other wheel in the opposite direction before it spins the driveshaft. However, all you need is something to cause a little bit of binding in the spider gears and it will turn the driveshaft first. While this will probably be a rare occurrence, my own methodolgy is one of being reasonably certain. Considering that putting a car in gear is a simple thing to do, I prefer to test by locking the driveshaft.