Measuring LSD Breakaway Torque

[Vlad Soare]

Hi,

If you have a clutch-type limited slip diff and want to know if the clutches are still good or are in need of a replacement, you can measure the breakaway torque by raising one rear wheel, shifter in neutral, handbrake off, and rotating the wheel with a beam-type torque wrench. But using the torque wrench on a wheel nut wouldn't be too accurate, since the point where you applied the torque wouldn't coincide with the one where you actually wanted to measure it (i.e. center of the wheel). I believe there are tools made specifically for this purpose, to allow you to attach a torque wrench to the wheel in such a way that it is concentric with the wheel. But I don't know how they are called and how they look like, so I don't know how to search for them. Do you happen to know where I could find something like this? Or at least how it's called, and I will take it from there. "Breakaway torque measuring tool", or combinations of words to that effect, didn't seem to return any meaningful results.

Thank you.

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[WD Pro]

Hi,

If you have a clutch-type limited slip diff and want to know if the clutches are still good or are in need of a replacement, you can measure the breakaway torque by raising one rear wheel, shifter in neutral, handbrake off, and rotating the wheel with a beam-type torque wrench. But using the torque wrench on a wheel nut wouldn't be too accurate, since the point where you applied the torque wouldn't coincide with the one where you actually wanted to measure it (i.e. center of the wheel). I believe there are tools made specifically for this purpose, to allow you to attach a torque wrench to the wheel in such a way that it is concentric with the wheel. But I don't know how they are called and how they look like, so I don't know how to search for them. Do you happen to know where I could find something like this? Or at least how it's called, and I will take it from there. "Breakaway torque measuring tool", or combinations of words to that effect, didn't seem to return any meaningful results.

Thank you.

What size is the nut on the driveshaft ? Could you use that with the wheel centre cap removed ? (If the socket will pass through the hole)

WD

 

[Vlad Soare]

That's a good point. I don't know, but if other cars I've seen are anything to go by, then it should be somewhere around 30mm, give or take.
Good point, I'll take a look at that.

 

[WD Pro]

Even if you can't get a socket through the wheel hole - just take the wheel off ? (Or is that what you are trying to avoid ?)

WD

 

[Vlad Soare]

No, I've no problem taking the wheel off.

 

[RagmopInKona]

Hi,

If you have a clutch-type limited slip diff and want to know if the clutches are still good or are in need of a replacement, you can measure the breakaway torque by raising one rear wheel, shifter in neutral, handbrake off, and rotating the wheel with a beam-type torque wrench. But using the torque wrench on a wheel nut wouldn't be too accurate, since the point where you applied the torque wouldn't coincide with the one where you actually wanted to measure it (i.e. center of the wheel). I believe there are tools made specifically for this purpose, to allow you to attach a torque wrench to the wheel in such a way that it is concentric with the wheel. But I don't know how they are called and how they look like, so I don't know how to search for them. Do you happen to know where I could find something like this? Or at least how it's called, and I will take it from there. "Breakaway torque measuring tool", or combinations of words to that effect, didn't seem to return any meaningful results.

Thank you.

You'd have to make an extention that one end had the 1/2 drive mount for the socket and the other end a 1/2 drive square inline with the tire tread , to mount the t/wrench to to get the same leverage as the tire.
Or just put the rear of the car on stands, wheels off, one side a long enough breaker bar that touch the ground keeping it from moving and socket, the other side the t/wrench and socket and try to turn the t/wrench in the same direction as it(the nut) turn with vehicle moving forward. As I'm sure the break away numbers will be different in reverse than in the forward rotation. Test this with the diff at operating temp or the numbers will be meaningless.

 

[junits15]

Wouldn't turning from a lug be fine? You just need the distance from the center of the hub to the center of the lug. If your wrench is x feet long and the distance from a lug to the center of the hub is y feet, the torque value read on the wrench will be {x/(y+x)}% of the actual torque to turn the wheel.

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