Engaging the 4WD

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scoot
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Engaging the 4WD

Post by scoot » Tue Oct 04, 2016 9:45 am

New to the Pinz scene (710) and about to do some off roading with her and I am curious about how I should engage the 4WD. I have the Operating instruction book but it is hard to understand the interpretation.
So, when switching the "control lever for reduction gear box" from road to off road I need to be in 4th or 5th gear moving 18 to 22 mph? And I have to be in gear, in motion when switching on the 4wd and the axle locks, correct? How about when disengaging the same levers, in gear in motion? Also, when changing the tranny oil, how much Redline MT90 does it take in gallons?
Thanks in advance. :D
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pcolette
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Re: Engaging the 4WD

Post by pcolette » Tue Oct 04, 2016 10:28 am

Transmission takes 2 quarts of MT90. Fortunately not gallons considering the cost of the stuff. :)

I have my method of engaging the various levers which may or may not be the best way so take this with a grain of salt:

-HI/LO I only shift when stopped, in neutral
-4WD I engage while stopped or moving at less than 15 mph but not while accelerating.
-Rear diff lock I use while stopped or moving less than 5 mph and not accelerating
-Front diff lock I almost never use but engage at less than 5 mph and not accelerating. Steering becomes very stiff with this engaged.

Again, this may not be the best methods so hopefully others will chime in.

Have fun and welcome!
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Re: Engaging the 4WD

Post by rmel » Tue Oct 04, 2016 11:03 am

Ditto here Paul, pretty much my method as well.

At the trail head I enable Lo and 4WD as the default. Then engage rear lockers as required.
Front lockers only when absolutely necessary e.g. deep sand, or up grade with loose gravel
a low traction situation -- I will do that on the fly. As Paul pointed out it's a bear steering
with front lockers on, esp. if you have obstacles to navigate around.

Of course, air down before you even get to your lockers, 18-22 lbs if you don't have bead lockers.
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Re: Engaging the 4WD

Post by VinceAtReal4x4s » Tue Oct 04, 2016 2:52 pm

The most important thing to keep in mind when engaging 4x4 or the lockers is to make sure you aren't turning at the time, and that you have no individual wheel spinning a different speed than the rest.

Always engage lockers well before you need them, never during your time of need.
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Re: Engaging the 4WD

Post by scoot » Tue Oct 04, 2016 3:01 pm

Thank you all. That is what I thought, Just wanted to make sure.
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Ian
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Re: Engaging the 4WD

Post by Ian » Wed Oct 05, 2016 3:31 am

What Vince said is most important, road speed is almost irrelevant (can't really think of a reason you'd want to move any of the levers at high speed anyway) The point is, all the wheels must be revolving at the same speed and heading in a straight line. If I get caught out on a long hill climb and have a need to engage a locker, if you very briefly back off the gas (to ensure there is no wheel spin) and drop the locker in, you can then get straight back on the power without too much loss of road speed.
Regarding the high/low shifter, it has synchromesh (very unusual in most 4x4's), so you can shift when moving. I'd probably not do it in 4th or 5th as you mention, but at low speed it is fine

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Re: Engaging the 4WD

Post by TechMOGogy » Wed Oct 05, 2016 8:32 am

Ian wrote:
SNIP

Regarding the high/low shifter, it has synchromesh (very unusual in most 4x4's), so you can shift when moving. I'd probably not do it in 4th or 5th as you mention, but at low speed it is fine
That I did not know!
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Re: Engaging the 4WD

Post by Twin Pinzies » Wed Oct 05, 2016 8:58 am

I'm almost always rolling when I engage the 4WD lever. Same with shifting the transfer case.
But I NEVER engage the lockers when ANY wheel is spinning out!

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Re: Engaging the 4WD

Post by 63rover » Wed Oct 05, 2016 10:37 am

The truck has to be moving for 4 wheel drive to engage. I learned this the hard way. I had the embarrassing experience of being pulled off a slippery patch of grass by a Ford F150 of all things with an old piece of jut scouting rope. Rear locker engaged but no 4x4. Wet slick, slimy grass and a laughing cub scout father! I am still reminded by other scouters.

As for lockers, I agree with being careful and making things last as long as possible however this is a military truck designed to save your life under fire. No enemy is going to nicely stop attacking while you slow down or stop to gently engage your lockers and wait for you to say okay when you're ready! YOU'RE DEAD! Pull the lever as soon as it is needed. Just before the need is better but no always possible. If a wheel is already spinning violently then yes, too late but the other axle will likely keep you moving and allow the out of control wheel to gain traction and then that axle can be locked too. When choosing a locker rather than both don't avoid the front because of a little extra steering effort. Front wheel lock, like front wheel drive is great for pulling you through or onto a problem where rear will only push you into it more. Rear lockers and posi-track are only more common on lesser vehicles because they are cheap and built for shallow civilian pockets. Thankfully for us government pockets are deep and set us up with the best.

The transfer case has synchro-mesh for the same get away for the nasty bad guy reasoning. As for shifting speeds, look at the little max speed chart by the wiper motor. 1 high equals about 2 1/2 low. Now think 10 speed bike. If I have slowed to 2 or 1 in high and need lower ratios still I hold the clutch, shift to neutral, shift the transfer case to low, release the clutch to get everything nicely synchronized, (blip throttle because I learned on a crash boX that had no synchro), clutch and select the gear I want (1 for almost stopped, 2 for walking pace and 3 for jogging) and release the clutch. Seems long and complicated when it is all spelled out but it can happen reasonably quickly before all momentum dies. Low to high is similar on the fly. I usually find 3 low to 2 high is a good crossover.

Have fun!

Cheers, Clive

PS Ever notice that the lockers tend to have minds of their own too? Pull or release a lever and the the light will come on or turn off to indicate success only after everything lines up just right for the action to take place.

PPS One last thing, Never force a stuck lever on or off. I only had this happen once. Some gentle back and forth released the problem. If it refused to let go I would have had to jack up one side of the offending axle to release the binding pressures.

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Re: Engaging the 4WD

Post by undysworld » Wed Oct 05, 2016 12:45 pm

Transfer case shifting is speed dependent. It can be done stationary or moving, but there are a few rules.
Shifting the transfer case from Lo to Hi can be done without concern for over-revving the drive train. At worst, you will be in too high of a gear in the transmission and have to downshift.
But when shifting the transfer case from Hi to Lo, you MUST be sure you will not over-rev things. Your vehicle speed must be slow enough that when you shift from Hi into Lo range, you are at an appropriate speed for the gear you will be in. For instance, here is no appropriate gear in Lo range for 50 mph (you cannot reach 50mph in Lo range), so if you shift into Lo at 50mph you will have issues.
63rover wrote: The truck has to be moving for 4 wheel drive to engage.

PS Ever notice that the lockers tend to have minds of their own too? Pull or release a lever and the the light will come on or turn off to indicate success only after everything lines up just right for the action to take place.

PPS One last thing, Never force a stuck lever on or off. I only had this happen once. Some gentle back and forth released the problem. If it refused to let go I would have had to jack up one side of the offending axle to release the binding pressures.
The truck does not necessarily HAVE to be moving to engage the lockers, depending on how things line up internally. But you do want to be a bit gentle on them.

Pulling a locker lever down puts pressure on the locking mechanism. It acts by sliding a collar around two splined shafts, thus locking them together. If the splines align with the collar, it will engage directly - even if the truck is parked. But if the splines do not align with the collar at that point (very common), a spring is depressed which maintains pressure on the collar. As soon as the splines do line up, the spring engages the locker. The indicator light will only illuminate AFTER this locking has happened. This is why the indicator light may not illuminate immediately when the locker lever is pushed down.

Same thing happens when you release the locker lever. The locking mechanism will unlock immediately unless the gears are loaded. If the gears are loaded under pressure (maybe due to turning, etc.), then the locking mechanism may stay engaged until the pressure is relieved (like by clutch in or going straight for a while). The indicator light will only go out after the locking mechanism has actually disengaged.

If you lift the locking lever but the indicator light has not yet gone out (locking mechanism is still engaged, likely due to loaded gears) and you then try to push the lever down, you will be trying to force fluid into an already filled slave-cylinder and the lever will feel like a rock. Further force will break the lever mechanism. The locker must disengage and the indicator light must be out before you can again push the locker lever down safely.

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Re: Engaging the 4WD

Post by 63rover » Wed Oct 05, 2016 10:22 pm

Great points about high to low range and revs. That is why I referenced the max speed plate. It is a handy reference wit the truck.

Thanks for explaining the internal mechanism workings.

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Re: Engaging the 4WD

Post by Texas710 » Mon Oct 10, 2016 9:11 pm

Also,

Do not use the front locker on pavement, or at least don't try and turn if the front lockers are engaged on payment... Bad things can happen. At least that was the previous owners warning to me

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Re: Engaging the 4WD

Post by scoot » Tue Oct 11, 2016 9:12 am

Thank you all again.
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Re: Engaging the 4WD

Post by undysworld » Tue Oct 11, 2016 10:34 am

Texas710 wrote:Also,

Do not use the front locker on pavement, or at least don't try and turn if the front lockers are engaged on payment... Bad things can happen. At least that was the previous owners warning to me
For the most part, you don't use any of the lockers on dry pavement. Bad things can indeed happen, like loss of control or internal damage to the truck.
When you go around a corner, the outer tires travel farther than do the inner ones. That's why your vehicle has a differential. Locking the front or rear differential/s will force both inner and outer tires to turn at the same speed, making any cornering more difficult. Making corners despite this difficulty will result in stress on the drive train.
When making corners, the rear tires don't exactly follow the front tires, which is why many 4wd vehicles also have a front/rear differential. But a Pinz doesn't have a front/rear differential, which is why you don't drive a Pinz on dry pavement with the front end locked in. Similarly to the axle differential lockers, cornering with the front axle engaged (1st lever) puts stress on the drive train.

The only time I've used a locker on dry pavement is to diagnose an unbalanced internal drive shaft on a 710.

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Re: Engaging the 4WD

Post by Jimm391730 » Tue Oct 11, 2016 3:20 pm

A bit more information: All locker levers in the Pinz move a "dog" (a collar with internal spines) along a splined shaft. Two splined shafts but up against each other; with the dog slid back over just one of the shafts, both are free to move at different speeds and directions. Pulling the lever slides the dog so that it bridges the gap between the two shafts and effectively combines them into a single shaft. When done correctly (meaning that the dog slides the full, expected difference) the shafts can handle a very significant torque. This is what makes the lockers so powerful when in poor terrain; for example one rear wheel can get all the torque to keep the truck moving.

But during engagement the dog needs to move the full amount; if you are already stuck, for example, the splines of the two shafts may not be lined up so the dog can't even begin to engage the other shaft. One shaft or the other needs to move so the spines line up and the dog can move across the gap. But if the dog only barely gets across to the other shaft and starts to transmit torque it will bind up and not slide any further. The small amount of spines that are engaged will not be able to transmit as much torque as it was designed to transmit (when engaged fully) so it is possible to damage the spines at the end of the shaft or at the end of the dog; if this happens then the dog can't move freely - it may not be able to fully engage, and may not be able to disengage. Damage like this is EXPENSIVE to correct.

So the best approach is to give the dogs time to engage and be able to do so with minimal torque applied. This will happen when the shafts are turning at just barely different speeds like when being driven "normally", in a reasonably straight line. The shafts do not need to be stopped; it is their difference in speed that is important. This means engaging the front axle before you need 4x4, when the front axle is just rolling and the rear axle is being driven (the rear will be turning just slightly faster than the front). Similarly, the diff locks will engage best when in a VERY slight turn but generally, off road, the terrain is rough enough that each wheel takes time moving just a bit faster than the other wheel, back and forth, all the time. DO NOT wait until you are stuck, spinning the wheels, and then try to pull a lever - the dog will try to engage, just begin to do so, then get all the torque and bind up to prevent full engagement. If you ever get into this situation then push in the clutch, pull the lever, and gently try to move so the splines get lined up and the dog can engage fully. You can also gently transmit torque in both directions (forward/reverse) to give the dog as much time and freedom to get fully into position. Then you can spin the tires to your heart's delight without damaging the lockers.

Lastly, if all levers are down then all four wheels must turn at the same speed. This can only happen when driven perfectly straight (and the tires all have the same diameter - don't mix and match tire brands and sizes). Any turn will require all four tires to spin at different speeds; off road, on loose terrain, wheel slip takes care of the tires needing to travel at the same speed during a turn. But on pavement with its much improved traction, the tires will try to move at different speeds but they can't - something has to give. We hope the tire(s) will slip but worse things could happen and this is why it is never recommended to use the levers on pavement (slippery conditions in the winter are the exception).
Jim M.
712W and 710M

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