Bw 1339 and lockers

[Yogi]

Muchas thank yous for your answers. Do you think front and rear truetracs would kill the case? I had thought such an arrangement would maybe be the ultimate all around q-track set up. Maybe not?

[Stuka]

As I recall, Eaton advises against a front tru-trac in a full time system as it can start to tighten up from regular driving. But It would be worth contacting them and checking.

[tgreese]

If I may comment here ...

I would think you'd have two problems with the lockers or limited slip in a Quadratrac vehicle.

First it the issue of drivability and safety. One issue you have with a locker in the rear axle is unpredictable steering. It's less bad with a longer wheelbase (longer lever arm) but the CJs especially can be a handful on pavement in slippery conditions. An unexpected patch of ice can send you sideways, or off in a direction you did not expect.

Open differentials are much more benign in this respect, because of how they work. Realize that an open differential splits total wheel turns between the two wheels, depending on which wheel has the least traction. Turn the driveshaft say, 3.31 turns, and you get two full wheel turns from the rear axle. On straight ahead pavement, that's one wheel turn for each wheel. However, if one wheel is on ice, that wheel will turn two times and the other wheel will turn none, adding up to two full wheel turns. Same thing happens when you put the car in the air, lock the driveshaft and turn one wheel: the other wheel turns an equal and opposite amount, adding to zero turns of the driveshaft.

Going around a turn, one wheel slows down and the other speeds up. The number of turns adds up to twice the total turns of the driveshaft divided by the axle ratio, same as straight ahead. No motion is lost, but instead it's divided (differenced, a differential) between the two wheels depending on the distance or traction at each wheel.

A locker is different, in that the wheel with least difference 'calls the tune.' When you go around a turn, the inner wheel - with the shortest path - turns exactly the number of turns of the driveshaft divided by the gear ratio. There is no more difference-ing. Instead, the wheel with the longer path speeds up to match the difference it must travel. A Detroit, for example, ratchets to allow the outer wheel to speed up and match the distance traveled. An LSD is somewhere between a locker and an open, allowing the inner wheel to slow down some while the outer wheel speeds up some, moderated by some kind of clutch pack or such.

I'd expect you to have some loss of steering control in a Quadratrac vehicle with LSDs or lockers. That AMC did not offer the usual rear TracLock LSD with the Quadratrac seems telling. Looking at the list of axles in the parts book, I don't see any evidence that the TracLock was offered with the Quadratrac. The TracLock has no detectable effect on handling even in the CJ - there is a reason why it was not offered with the Quadratrac. (I kinda think this was to preserve the very popular handling characteristics of the Quadratrac wagons in snowy weather - the all-weather commuter, so popular for SUVs today.)

You can see that a locker with loss of traction on an ice patch would tend to drag the back end of the Jeep in the direction of the wheel with traction. This should not matter if you are going straight ahead. In a curve, it would be like understeer or oversteer, depending on which wheel loses traction.

This is getting pretty long - I will come back and finish it later.