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Detroit Lockers

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#1 cedarsf1

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Posted 08 November 2018 - 07:13

Can anyone explain how a Detroit Locker operates? When does it lock up, and when is the diff open?


How do you drive a car with one of these--mainly how do you avoid the terrible understeer that is characteristic of this type of LSD?


#2 Fat Boy

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Posted 08 November 2018 - 18:57

Honestly, do a bit of research for yourself. This is not a difficult thing to search.


1. It fully locks the wheels with across the axle when a certain drive torque is applied (regulated based on the internal spring).

2. It fully locks (like a spool) on throttle and acts as an open differential without drive torque (off-throttle).


To drive:


The main problem with a D.L. is the fact that it's completely open during braking and corner entry. This provides no yaw stability through the complete unlocking of the rear tires. There is no preload with a D.L.


Detroit lockers are primarily used on tin-tops. These cars have relatively high C.G.'s. When cornering steady-state, the inside rear tires are very light and they don't provide a large understeering moment. The 'terrible understeer' is largely based on people who haven't actually worked with differentials. It does mean that when driving a car with a D.L. (or a spool), you need to be patient before applying throttle mid-corner and allow the car to rotate. When you go to throttle, the car is going to continue to turn, but less so than a car with an open differential. Honestly, this is the correct way to drive regardless of the differential. Most plate-style differentials act in a very similar manner. They're not nearly as variable or smooth as we often portray them. Generally speaking, at some low throttle input level (5-20% depending on setup) the rears lock solid in a relatively abrupt manner.


The place where you can run into problems is when you have on-throttle directional transitions (i.e. an 'S' section of a track). To get the car to transition, you may have to fully lift off the throttle to get the diff to disengage and allow the transition. The other option (and one more commonly used) is to just be more aggressive with the steering inputs and get the car a little loose to rotate. The tuning option that you have with a D.L. is the release spring. The stiffer the spring, the more difficult it is to make the differential unlock. The softer the spring, the easier it is to get the differential to unlock. In general, when you're driving a locked rear end on the car, you need to be patient enough to allow the car to rotate. When you go to throttle, you need to do be able to do it once and commit to it. Hopping on and off the throttle is not suffered gladly. If the car understeers, you need to lift, botch the corner and fix it the next lap by being more patient. If the car oversteers, stay on the gas and catch the slide.

#3 cedarsf1

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Posted Yesterday, 12:56

Thanks for the detailed response!

You mentioned the release spring used for tuning the D.L. So you can tune how easily the unit locks and unlocks, correct? But once it's locked, it's 100% locked, unlike the operation of a Posi or a Torsen, correct?

#4 Greg Locock

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Posted Today, 00:07

Spot the deliberate error in this http://www.eaton.com...detroit-locker/