Shouldn't a limited slip diff stop this?

[deadpan_delivry]

I've got a sloping driveway and was trying to work out what the strange noise was when I reverse out too slowly. Decided to test it and one of the rear wheels lifts slightly off the ground and starts spinning.

However shouldn't the LSD kick in and stop it from spinning? The other wheel isn't spinning so after it starts to slip it should lock right? Unless there is a mode to engage it?

Perhaps someone with more knowledge of these things can answer - Thanks in advance!

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[KingKona]

I've got a sloping driveway and was trying to work out what the strange noise was when I reverse out too slowly. Decided to test it and one of the rear wheels lifts slightly off the ground and starts spinning.

However shouldn't the LSD kick in and stop it from spinning? The other wheel isn't spinning so after it starts to slip it should lock right? Unless there is a mode to engage it?

Perhaps someone with more knowledge of these things can answer - Thanks in advance!

I believe with a Torsen LSD, if one wheel has absolutely 0 traction, you'll be stuck. As long as there's at least a little traction to both wheels, power will go to the wheel with the most.

https://www.kmpdrivetrain.com/differentials/torsen-vs-plated-limited-slip-differential/

" The car will not move with one of the wheels in the air. If one wheel is in the air or has no traction at all, it will only take very little torque to turn that wheel. It is necessary to apply torque to the gears to generate the required thrust force to maintain the bias ratio. Without torque, the gears will not be pressed together and no friction will be generated, so the gears can rotate freely. The unloaded wheel will have high speed, but can only transfer very little or no torque. The helical LSD will send torque to the wheel with traction according to the bias ratio, BUT four times zero still equals zero. This means the wheel with grip will not receive any torque and the LSD acts as an open differential. The plated LSD will have (limited) torque available to the wheel with traction due to the preload in the clutch pack."

 

[junits15]

I believe with a Torsen LSD, if one wheel has absolutely 0 traction, you'll be stuck. As long as there's at least a little traction to both wheels, power will go to the wheel with the most.

https://www.kmpdrivetrain.com/differentials/torsen-vs-plated-limited-slip-differential/

" The car will not move with one of the wheels in the air. If one wheel is in the air or has no traction at all, it will only take very little torque to turn that wheel. It is necessary to apply torque to the gears to generate the required thrust force to maintain the bias ratio. Without torque, the gears will not be pressed together and no friction will be generated, so the gears can rotate freely. The unloaded wheel will have high speed, but can only transfer very little or no torque. The helical LSD will send torque to the wheel with traction according to the bias ratio, BUT four times zero still equals zero. This means the wheel with grip will not receive any torque and the LSD acts as an open differential. The plated LSD will have (limited) torque available to the wheel with traction due to the preload in the clutch pack."

This is the right answer, but in real life the traction control should apply the brake a little bit which will cause the diff to re-activate and divert power to the other side.

 

[1MeanZ]

If you have a Torsen diff (PP1 or PP2, Mach 1) just put a few clicks in the e-brake handle and it should activate the diff and spin 2 just fine.

 

[Vertex]

I will note that I've felt this happen many times in my car due to a gathering on nearly every Thursday during weather permitted days for me. I have to go up it at an angle because the front end clearance my Mach is so low. Nearly every single time I go into the parking lot I can feel the rear end almost lock up for a second when I know one of the wheels is almost off or partially off the ground. I don't think there is anything abnormal or anything you can do about it and have never had an issue with the rear end in my car yet.

 

[deadpan_delivry]

Thanks for all the replies. Here is a video of it.

The tyre isn't completely off the ground, which is why I can hear the strange noise from the cabin. Perhaps I am missing the point of an LSD but I thought that it was supposed to lock the wheels if one starts to spin? Based on your replies it seems that at some point it loses all traction then becomes a free spinning wheel.

I'm not too worried about it as I can avoid it by coming out faster and smooth, but if there is a way it could be locked it'd be useful.

Thanks again!

 

[WD Pro]

You have all jumped on the Torsen …

That’s a RHD Aus car, so it’s like a PP1, but without a Torsen.

Unless the OP has been busy with the spanners, it’s a Trac Lock diff

WD

 

[ihasnostang]

i too am a victim, but i have a torsen and intentionally came to a stop when it picked a wheel up

 

[deadpan_delivry]

Thanks for all of the replies and I should have mentioned that I'm in Australia RHD.

TIL about LSDs and how they work. I'm just glad I'm not doing something damaging to the car - although reducing it as much as possible is ideal as I'm sure it loses a little bit of rubber every time it spins. You can see the tyre marks on the ground..

 

[velocityblue5.0]

i know it doesn't apply to this, but just gotta say i'm loving the yellow accenting on that color! looks sick

 

[ice445]

There's not enough load to lock up the Trak Lok setup, that's all. If you actually put it under power you'll see it work as designed.

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