Using Lockers on Steep Descents

[Twisty]

Something I've always wondered, and even more now that I have lockers that I can turn on and off, should you use your lockers when driving down steep descents......

I know you wouldn't use the front as it effects the steering a little....but should the rear be in if it looks like you might lift a wheel here and there?

I know in my 4runner, which is unlocked, when going down a long, rutted steep decent (ie. Club Rally at LCMP), when ever the rear wheel would lift, the car would speed up until the airborne tyre grabbed terra firmer again. If the rear diff was locked, I'm guessing this would prevent this?

[taziiy]

I only have the rear locker and most of the time im out 4wding its on wether its flat up hill or down hill

[Humpy]

I use my rear locker all the time

Helps stop the runaway when you lift a rear wheel

[Peter @ Aawen4x4]

If you have an open diff, or your lockable diff is not turned on, when one rear wheel lifts, the open diff will allow the lifted wheel to spin backwards at double the driven speed. That also allows the wheel on the ground to spin forwards at double the speed. If this occurs when one front wheel is on a surface with marginal traction, and the same occurs at the front, you CAN end up with a very uncontrolled lurch downwards for about 6 feet, at double the driven speed!! If the vehicle doesn't regain traction at the end of that lurch, you're a passenger until you hit something big enough to stop you!

Locking your diff removes the possibility of this happening short of a major mechanical failure!! Why wouldn't you want to lock the diff on a steep downhill run!!!

[brooksy]

As you know Dave I have a locker in the rear & I use it on steep descents as I will not use that Hill Descent on the Disco anymore after what Gidget told me !!

brooksy

[mike_fnq]

If you have an open diff, or your lockable diff is not turned on, when one rear wheel lifts, the open diff will allow the lifted wheel to spin backwards at double the driven speed. That also allows the wheel on the ground to spin forwards at double the speed. If this occurs when one front wheel is on a surface with marginal traction, and the same occurs at the front, you CAN end up with a very uncontrolled lurch downwards for about 6 feet, at double the driven speed!! If the vehicle doesn't regain traction at the end of that lurch, you're a passenger until you hit something big enough to stop you!


I've experienced this first hand, very scary! In most situations, I'd keep 'em both in!
(Waddaya know Peter, we agree on something ;))

[bad_religion_au]

If you have an open diff, or your lockable diff is not turned on, when one rear wheel lifts, the open diff will allow the lifted wheel to spin backwards at double the driven speed. That also allows the wheel on the ground to spin forwards at double the speed. If this occurs when one front wheel is on a surface with marginal traction, and the same occurs at the front, you CAN end up with a very uncontrolled lurch downwards for about 6 feet, at double the driven speed!! If the vehicle doesn't regain traction at the end of that lurch, you're a passenger until you hit something big enough to stop you!

Locking your diff removes the possibility of this happening short of a major mechanical failure!! Why wouldn't you want to lock the diff on a steep downhill run!!!


pete, how does a detroit go in this situation... wouldn't it allow the wheel on the ground to be "ground driven" faster than the speed travelling, resulting in the same effect as an open diff? i haven't experienced it so i don't know, as the rear of my cruiser has enough travel to prevent this happening

[crankycruiser]

Id definatly use at least my rear.. maybe even front if it looked scary enuf

[Humpy]

If you have an open diff, or your lockable diff is not turned on, when one rear wheel lifts, the open diff will allow the lifted wheel to spin backwards at double the driven speed. That also allows the wheel on the ground to spin forwards at double the speed. If this occurs when one front wheel is on a surface with marginal traction, and the same occurs at the front, you CAN end up with a very uncontrolled lurch downwards for about 6 feet, at double the driven speed!! If the vehicle doesn't regain traction at the end of that lurch, you're a passenger until you hit something big enough to stop you!

Locking your diff removes the possibility of this happening short of a major mechanical failure!! Why wouldn't you want to lock the diff on a steep downhill run!!!


Thats not exactly true

The unlocked wheel opposite the one in the air will do ground speed. Providing no resistance or propulsion

As you said, if this happens at front and back simultaneously you are riding a billycart (not necessarily double the speed) until at least one axle has traction on both sides

[Ford Mav]

definitely use of lockers on this side of the fence. Gives u better traction control hence better engine braking due to lack of slip.

My 2 cents worth

Frank

[Peter @ Aawen4x4]

The good news about Detroits, and to a certain extent the Lokka's and Lockrites, is that they also lock in deceleration! When you are in this situation and the force of gravity exceeds the driving force from the engine (that's why we use low range and low gear) the diff lock works as though the driving force is coming from the tyre, not the engine, and the whole lot works in reverse. (just like it would if we backed up a hill!)

In effect, the wheel on the ground becomes the locked wheel, with its side of the locker holding the axle and the drive shaft to the same speed, and 'cos you got the engine on the other end, thru the gearbox & transfer case, it can't run on faster; while the wheel in the air is just hanging there turning at the same speed, 'cos there's nothing to disengage it. It's effectively the same as the Detroit working in reverse, if they didn't, we'd be in the situation the Humpy describes, in a billycart and on our way downhill!! FAST!

In practice, going over the lip of a steep hill in low range & low gear, in a vehicle fitted with a Detroit, you can feel the tyre tread travel thru the disengage/engage action in the space of the tread travelling about 4 inches over the ground. It is a very slight 'lurch' that many people never notice, but if you expect it, you can feel it! That is the Detroit passing thru the ground driven faster stage, then into the decelleration phase of locking "in reverse" and slowing the vehicle as it runs down the hill. When we tried this on a vehicle with an EZE-locker, the same concept as a Lokka or Lockrite, we discovered that you have to get into the decelleration stage fairly quickly, and perferably before you've gone too far, cos the differnt lock/unlock methods give you about 2 feet of disengagment before locking again, and if you get too fast in that 2 feet, you can be stuck unlocked! The lurch can be very noticable, or just begin and then never finish. That's the OH S#!T stage as you begin to roll down the hill like a billy cart. The Detroit Series IV Softlocker doesn't give you this feeling!!

[bad_religion_au]

thanks for that, i often wondered what that lurch was... i knew it was to do with the locker because it started when i put it in

[kingchevy]

I've used my lockers in the yellow car on some very very scary hill descents (my heart stopped at one point I;m sure) and I think without the lockers ingauged the truck would have been uncontrolable I was in 4low 1st diff locks enguaged I didnt dare touch the brakes so I was doing about 45 clicks at one point but as soon as I started getting sideways I would sortof slowly applie the gas and would gain traction back I even managed to stop have way down on a lip any less traction and I would have been going over a very steep bank on the way up I was in high range 2nd and without the power of the v8 diesel I wouldnt have made it because I got half way up before relising the situation I was in so the only thing I could do was gas it and only just made it up over the top lip if I had of stopped on the hill I would of had to back down and I dont think the brakes would have held me there it was all slippery clay rubbish.