Originally Posted by pazur
So you are saying that gear-driven detroit behaves different than lunch box lock-right or aussie on dry pavements?
That's EXACTLY what I'm saying.
Full time lockers lock, unlock, drag/spin the off side tires, make all kinds of jerking, popping, ect. when you are going around corners on pavement.
They only have TWO settings, Locked & Unlocked,
And as little as three inches of tire rotation will lock and unlock them,
Axle shaft speed differential is what determines if they lock or unlock, and you have no 'Practical' control over when they lock or unlock.
With a Detroit TrueTrac (and other gear driven Limited Slip differentials) they use a series of gears in the case to 'Sense' when one wheel needs power and the other needs to free wheel...
The ones I'm running is a 70/30 split, so one wheel can be running 70% faster around a corner and still get at least 30% of the power, BOTH still getting power and traction.
Here is a image of the 'Guts' of a TrueTrac, no locking 'Teeth'....
Like I said, it's the next evolution in 'Limited Slip' differentials... And it's been around since the early 70s when it was practical to produce.
Since there isn't anything 'Locking' or 'Unlocking',
Both wheels are being driven at all times, but at different rates to accommodate the varying speeds of the wheels, but both wheels get some percentage of power full time.
Mine will still pull it's self with one wheel completely off the ground since no matter what, I'm still getting 30% of the power to the wheel that HAS traction...
That wouldn't happen with a clutch pack limited slip since the wheel with traction would 'Slip' the clutches and the one with no traction would simply spin (at TWICE the rate the speedometer registers!)
I doubt (yet I never driven detroit). All these auto lockers momentarily unlock when there is pre-set difference of forces between wheels.
Actually, it's differential between drive shaft rotation and axle rotation.
One axle isn't driving 1:1 with the drive shaft, the locker engages.
Tolerances in the spacing of the locker engagement teeth (or pins) determine how much one axle gets to goof off before the locker teeth reach each other,
So there really isn't any practical way to set a locker up for when it engages or disengages.
As long as the axles speeds are even, the locker doesn't force the driven plate teeth (axle) into the drive plate teeth (differential) and you have an 'Open' differential.
When you have one axle moving slower (or sometimes faster) than the other axle/carrier, then the forcing mechanism kicks in automatically and LOCKS the axle that is not moving with the carrier into the carrier.
You don't get ANY say in the matter, it 'LOCKS' one axle (or BOTH axles) into the carrier when the axle speed isn't the same as the carrier speed,
And that causes REAL problems when you are on slick pavement, makes a BUNCH of noise, and is generally unsafe since it CAN cause the back end of the vehicle to break loose and do something it shouldn't in traffic.
That's why nothing but a few 'Racing Only' muscle cars came from the factory with true lockers,
And why there are so many designs of 'Limited Slip' & 'Posi-Track', 'Track Lock' differentials out there that DO NOT lock the rear wheels together.
They were simply unsafe on the street for the 'Average' driver and caused accidents...
Accidents cause law suits, and they didn't need the law suits so they don't use them.
To date no one has been able to design a locker that behaves like open differential on road and turning and locker off road/straight movement without human/computer control.
That isn't entirely a true statement.
The Gear Driven Limited Slips have been used in racing for quite some time because of their very nice high speed operation.
We used them in Indy (Champ) cars in the very early '70s and they gave us an edge on the people that weren't using them,
Thorsen-Gleeson designs have been permeating racing since the early 70's, and the Detroit TrueTrac is living proof the concept exists and works well.
The 'Stabili-Trac' system uses a gear driven limited slip,
It simply hazes a brake on the spinning wheel, and the differential lets the braking of one wheel at a time where you couldn't do that with a locker.
Staili-Trac also reduces engine power, and that is purely electronic with modern fuel injection.
I took a modern full size SUV out and TRIED to make it spin in the snow on a parking lot this year, and it simply WOULD NOT spin a tire with the traction control turned on!
You COULD NOT make it spin a tire or lock up a tire!
Couldn't do that with a 'Locker'....
We did, however, still have all 4 wheels turning when we decided to climb snow piles with it!
For example, when turning right, the right wheel force push to the rear and left wheel push to the front. This difference depends on speed, degree of turn and friction between pavement and tire. If any of these variable is low your jeep understeers with rwd in turning maneuvers, especially at low speeds and low traction (rain, snow, ice, mud). You can surely set this difference to be lower, however axle may then unlock even in straight movement (when we want it to be locked).
Now you are talking about an UNLOCKED front trying to seer a vehicle that is pushing from the rear...
I'm not saying if it's slick enough, you WILL NOT push the front in a straight line,
Especially if you brake hard (what most people do) and break traction with the front tires...
If you have a 'Locker' you will make the front tires 'PLOW' instead of 'Turn' while keeping traction.
If it's slick enough, ANY drive in the rear will do that same thing.
What I'm talking about is being able to let one rear wheel REDUCE or INCREASE speed in a controlled manner,
Allowing you to make a turn with *SOME* traction in the front.
When a locker pops 'In & Out' it can break what traction you have in the front, and you 'Plow' no matter what...
If you have NO TRACTION for the steering tires, you are going to 'Plow' no matter what,
But something like the TrueTrac lets you keep what ever little amount of traction you have in the front, and the vehicle still turns on command,
And/Or the back end doesn't come around you while you are trying to turn,
Like what OFTEN happens with a locker that decides to 'Lock' at the wrong time!
Manual locker is therefore the only rational way, perhaps not for a buggy that never sees a paved road.
Study up on the gear driven (non clutch) Limited slip units.
It's worked GREAT for me, and I don't have to worry about a little, short CJ-5 turning backwards every time the locker decides to do something stupid!
This TrueTrac has REALLY made my little 360 powered CJ-5 about 100% more drivable than the earlier Detroit Locker I had in there!
It was inherently unsafe on highways aorund here since this is farm country, nearly every side road, curve & intersection has sand, gravel, mud, grain...
(makes motorcycle riding interesting too!)
...Something spilled in it, and I had more than one 'White Knuckle Ride'
, followed by needing clean shorts