i4wd/Bypass Explanation

From this Facebook thread: https://www.facebook.com/groups/1099503223530752/posts/2201721543308909/

The STOCK Talon diff is a cam and follower type mechanical torque biasing diff. Mechanically, it works like a smoother version of a ratchet locker, allowing for more slip. It is capable of locking both sides together, but there has to be some traction on both tires to do it.

The Talon diff with a TORQ locker added is just a standard ratchet locker. Apply power and it pushes the teeth in and locks left/right together. It engages aggressively and can lock both sides together with traction only on one side.

i4wd comes into play in 2 ways:

1. Brake Traction Control (BTC) - Because the STOCK diff uses cams against ramps shaped followers, if you run out of traction on one side, the STOCK diff fully unlocks and the i4wd system will apply a small amount of brakes to the tractionless side which applies pressure to shift the cam plate and lock it back up. Only around 1/4 the brake pressure proportionate to the input torque is required because the cam and follower acts like lever and multiplies the force. It should only have a small effect on forward momentum, but if the system gets confused as it can in heavy mud and snow, it can cause some issues.

2. Torque Management - this is the one everybody really gets into trouble with. In i4wd, the ECU applies some clutch logic to try to save the clutches and prevent stalling if you get in a bind. Instead, it causes a "bogging" issue when normal clutch engagement is what is desired. It doesn't really do this in 2wd.

The Hess i4wd Bypass Kit basically does only 1 thing - apply 12v to the front drive clutch (on the input shaft into the diff). However, it has 4 total modes of operation:

Bypass ON/i4wd ON - i4wd active and front drive clutch locked on. This prevents the ECU from disengaging the front axle if i4wd goes into an error state.

Bypass OFF/i4wd ON - Normal i4wd operation, as if the kit was not installed.

Bypass ON/i4wd OFF - Torque management and BTC are disabled because it thinks it's in 2wd, but the front drive clutch is manually locked ON. Front diff does mechanical torque biasing and can drive both front in most conditions unless one experiences a total loss of traction.

Bypass OFF/i4wd OFF - normal 2wd operation.

Should you run a bypass kit if you have a locker? YES. The BTC part of i4wd WILL NOT activate when you have a locker because there won't ever be enough left/right variance to trigger it, but the clutch bogging from torque management will. You'll want to run Bypass ON/i4wd OFF when using the locker.

Should you immediately install a locker? NO. i4wd works great for most uses. If you experience the flapping/bogging because of driving up shelf rocks or in mud/snow, try the bypass kit. If the bypass kit isn't working for you, then consider installing the locker. Also take into consideration the locker adds a lot of additional mechanical stress, so your likelihood of breaking axles and housings, and more difficult steering are all potential side effects you'll want to consider first.