Hey guys VLSD question

[strokethefurrywalls]

Hey all, im strokthefurrywalls, ive got a 91 s13 and im a little bit confused about what i have for an lsd. My apologies if i am posting this in the wrong subforum, but i didnt think it was too technical. I was sold this car a long while back told i have a vlsd, but i never cared to check. LSD's are not my forte, but since im starting to do more drive line work i want to know what kind of lsd i have. it looks like the rear of an s13, but it has a sensor hanging out of it. a friend told me it could be from an s15, but im not too sure. im probably going to be pulling it out in a few days to drain the fluids, maybe ill figure it out then. these are the best shots ive got of it. in the second picture you can see a sensor coming from the top and dangling down near the drive shaft.

[Razi]

I think that's the sensor for the ABS system.
Probably because it's from a J30.

[AZhitman]

Simple way to tell:

Jack the rear up under the differential. Turn one rear wheel. If the other wheel turns in the SAME direction, you have a LSD. If it turns the opposite direction, it's an open diff.

[strokethefurrywalls]

okay ill figure give that a shot when i jack her up next. but how can i tell between the different types s13/s14/s15?

[biggie]

Definately has an ABS sensor, so would assume its a VLSD, either from J30 or swapped from another car.

[blkvrtswp]

To test without jacking car up, get one tire on blacktop and the other on grass. Rev high and dump the clutch hard. If you just spin the wheel on the grass you do not have VLSD.

[strokethefurrywalls]

To test without jacking car up, get one tire on blacktop and the other on grass. Rev high and dump the clutch hard. If you just spin the wheel on the grass you do not have VLSD.

thank you for all the responses, id love to dump the clutch but there isnt much left of it haha. Glad this is all cleared up.

[AaronMC]

Simple way to tell:

Jack the rear up under the differential. Turn one rear wheel. If the other wheel turns in the SAME direction, you have a LSD. If it turns the opposite direction, it's an open diff.

This method has often proven ineffective, the VLSD will act like an open diff if the viscous fluid is not hot. I tested it out on a J30, the wheels spun in opposing directions, but when I gutted the diff I found a VLSD.

Definately has an ABS sensor, so would assume its a VLSD, either from J30 or swapped from another car.

http://www.ka24development.com/vlsd.html Be careful when assuming ABS has a VLSD.

Another test would be to do a burnout on the asphalt and count your tire tracks, but with your clutch issue this is not an option.

[SX APPEAL]

I had a 91 LE that had ABS, but not an LSD, so it is possible. But honestly if that plug doesn't go to anything, then the diff is probably swapped and why would anyone swap in another open diff?

Jack the rear up under the differential. Turn one rear wheel. If the other wheel turns in the SAME direction, you have a LSD. If it turns the opposite direction, it's an open diff.

This method has often proven ineffective, the VLSD will act like an open diff if the viscous fluid is not hot. I tested it out on a J30, the wheels spun in opposing directions, but when I gutted the diff I found a VLSD.

You're both right. A Nissan R200V has a regular spider gear type open diff inside of it (albeit with 4 spider gears instead of 2) The only difference is that it has a viscous coupling within this assembly connecting the two output shafts (I've attached a link to a viscous coupling diagram below, which should help with the visualization) So when there is not a great difference in relative speed of the output shafts, the coupling will tend to let the wheels spin independently (or in opposite directions if the vehicle is jacked up with the trans in gear. This is how the diff lets you go around corners at normal speeds without completely locking the rear wheels together. However, when one wheel starts to slip under power, difference in the relative speed of the output shafts greatly increases, which creates friction in the viscous fluid and produces the locking force. Clutch type LSD's work the same way, they increase the clamping force on the clutch discs (aka the amount of lock) depending on the relative speeds of the output shafts. Clutch type's just do this a lot more quickly and effectively (read: "harshly')

Back to the VLSD, if you do the "jack up the rear end and spin the tires trick" with the car IN NEUTRAL, the wheels will both spin in the same direction. However, this is can also happen with an open diff with the trans in neutral. If it takes less force for the diff to just spin the un-engaged drive shaft than it does to spin the spider gears in the diff, then even with an open diff, your rear wheels will spin together as the driveshaft spins freely. The only way to be COMPLETELY sure that you have an LSD is to do the trick with the trans IN GEAR. When in gear, the engine provides a holding force on the rest of the driveline, so you know you're only testing the operation of the diff itself. Now when you turn the wheel, in the case of an open diff, the wheels will freely spin in opposite directions. If you have a VLSD they will also spin in opposite directions (because this diff still contains the spiders gears as I said before) but it will be very hard to turn the wheels at all, because even when cold, the viscous coupling still provides some locking force. This is the only surefire way of determining what type of diff you have without actually driving the car.

For you visual learners:

Here is a decent diagram of how a viscous coupling works

Hope this helps

[Mercury_Hg]

I had a 91 LE that had ABS, but not an LSD, so it is possible. But honestly if that plug doesn't go to anything, then the diff is probably swapped and why would anyone swap in another open diff?

Jack the rear up under the differential. Turn one rear wheel. If the other wheel turns in the SAME direction, you have a LSD. If it turns the opposite direction, it's an open diff.

This method has often proven ineffective, the VLSD will act like an open diff if the viscous fluid is not hot. I tested it out on a J30, the wheels spun in opposing directions, but when I gutted the diff I found a VLSD.

You're both right. A Nissan R200V has a regular spider gear type open diff inside of it (albeit with 4 spider gears instead of 2) The only difference is that it has a viscous coupling within this assembly connecting the two output shafts (I've attached a link to a viscous coupling diagram below, which should help with the visualization) So when there is not a great difference in relative speed of the output shafts, the coupling will tend to let the wheels spin independently (or in opposite directions if the vehicle is jacked up with the trans in gear. This is how the diff lets you go around corners at normal speeds without completely locking the rear wheels together. However, when one wheel starts to slip under power, difference in the relative speed of the output shafts greatly increases, which creates friction in the viscous fluid and produces the locking force. Clutch type LSD's work the same way, they increase the clamping force on the clutch discs (aka the amount of lock) depending on the relative speeds of the output shafts. Clutch type's just do this a lot more quickly and effectively (read: "harshly')

Back to the VLSD, if you do the "jack up the rear end and spin the tires trick" with the car IN NEUTRAL, the wheels will both spin in the same direction. However, this is can also happen with an open diff with the trans in neutral. If it takes less force for the diff to just spin the un-engaged drive shaft than it does to spin the spider gears in the diff, then even with an open diff, your rear wheels will spin together as the driveshaft spins freely. The only way to be COMPLETELY sure that you have an LSD is to do the trick with the trans IN GEAR. When in gear, the engine provides a holding force on the rest of the driveline, so you know you're only testing the operation of the diff itself. Now when you turn the wheel, in the case of an open diff, the wheels will freely spin in opposite directions. If you have a VLSD they will also spin in opposite directions (because this diff still contains the spiders gears as I said before) but it will be very hard to turn the wheels at all, because even when cold, the viscous coupling still provides some locking force. This is the only surefire way of determining what type of diff you have without actually driving the car.

For you visual learners:

Here is a decent diagram of how a viscous coupling works

Hope this helps

You are the bomb. I don't know if people say that anymore, but damn. There it is.

[nightheron]

I've got a super hicas model with a VSLD. There is a little tag on it that says so. Easiest way to tell of all. Best way to tell, see how it does in the mud.