Snow sliding technique- throw it in reverse?

[nakman]

On the Spooky Night Run there were a few guys who were employing a new technique to me, to reduce speed on steep icy descents. The feat was performed while the vehicle was essentially in a 4-wheel slide headed downhill on snow/ice, and was essentially locking up all 4 wheels, shifting to reverse, and giving it some gas to attempt to slow the vehicle down.

I was really surprised to hear guys were doing this, and without making it a big deal I did at least convey over the radio that "I'm not sure that's such a good idea." Seems to me like a good way to pop a pinion or birfield/CV (what if there was sudden traction on a locked axle), or just reduce friction even further to make the truck accelerate even faster.

But perhaps a revolution is at foot here and I'm just a late adopter, so would like to know if anyone else is using/recommending this method? discuss...

 

[farnhamstj]

Are you meaning sliding down hill backwards on ice? then yes.

 

[AimCOTaco]

I glad this came up as I was also questioning this technique after the run. I'm generally fascinated by all aspects of vehicle dynamics and this is not sitting right with me.

I'm familiar with shifting into reverse to maintain rolling control when sliding backwards but this is in fact a discussion of shifting into reverse while sliding forward.

To me it makes more sense to keep the wheels rolling and not slipping in the direction of travel in order to maintain steering ability (exactly why ABS helps with control). On that particular run after the first two slides I just left a ton of space to the next vehicle (like let him go until I could no longer see tail lights) and would keep rolling on the steep stuff while pulsing the brakes so that I could steer but did not slide as much.

I also wonder if the last vehicles would have encountered better trail conditions if this technique had not been used ahead of them? Either way this should be a great discussion.

 

[mcgaskins]

On the group snow run back in the end of January, we encountered a couple spots where the trucks in front had packed down the snow pretty well and with the low temps caused patches of ice. At one point in the trail, several of the trucks (including me) had to get up momentup to go up a small hill, lost momentum and slid backwards at a considerable speed. I had almost made it to the top on one attempt but got hung up on a rock and had to reverse out to try again, and when I put it in reverse and tapped the gas I started careening out of control backwards down the hill at probably 10-15mph which was honestly terrifying.

I took it out of reverse, put it in neutral for a second, then put it in drive and gave it gas to slow my backward slide knowing there were trucks and people back there. I was worried it would cause driveline damage, but I was more worried about hitting someone. Perhaps it was due to the extremely slick conditions where the lack of traction didn't cause binding, but I noticed no binding/banging/clanking or anything when I did it. It definitely did significantly slow my backwards slide and maybe prevented a collision.

My girlfriend looked at me afterwards and said she had never seen me that scared or move my feet and hands around the wheel and shifter so fast before!

Edit: here's a pic from the run

 

[HoneyBadger]

OK.
So, I'm the one who mentioned this that night. And I did use it, as well as at least one other person who used it to try and not rearend me.

I DO NOT RECOMMEND USING THIS TACTIC, except in extreme circumstances and only on VERY slippery surfaces, I.E. Ice/compacted snow or really slippery mud.

That night, I got to sliding pretty fast and right at a tree. I didn't even think about it, I just did it, and I stopped just shy of the tree. I used it later to stop after having picked up considerable speed trying to get away from an incoming FJ.

OBVIOUSLY this should only ever be done when ALL FOUR tires are locked up and NOT turning. And then you floor it, and then let off the brake, to produce initial backwards spin on the ice, thus giving uphill force on the vehicle while minimizing stress to your moving parts.

That being said, this obviously does put unwanted stress on your moving parts involved. And outside of a really slippery circumstance, should never be executed.

As far as it perpetuating the slippery surface for the later rigs coming down the hill... I doubt it, as there wasn't much snow left on the areas where I executed this move. I pretty much dug it out to the mud below.

That's just my $0.02 I know many of you will probably disagree with this, and think me foolish for using it. But, I made it out in one piece without hitting trees or other rigs. Seems legit to me. Hopefully I'll never have to use it again.
Thinking back about 7 years ago, I wish I had used this technique one rainy muddy night. Might have prevented me from hitting that oak tree at the bottom of a hill. Who's to know.

Bottom line: To each his own.

(side note) If this does get adopted for use in emergency situations, I call dibs on it. It will be know from now on as "Pulling a Shotshell."

 

[JadeRunner]

I can't say I've done that before. I suppose if you could get just the right amount of traction and a little "dig" it would help you. And if things were happening slow enough. The risk being as Tim said if you caught a rock or sudden traction it could break something.

 

[nakman]

Travis you just reminded me that I've done this before, but years ago and in a manual truck. Was sliding backwards, and I shoved it into 1st then dumped the clutch and peeled out forwards. Not sure if it did anything though, as it was only about a 5' long event. I still think it actually lowers friction to intruduce the other direction of wheel travel.. I also will sometimes experiment with neutral as opposed to any gear when on something steep, just so I'm not fighting the engine. But then once things lock up, I slam it down to L and start pumpin...

I also just remembered my sweet move from high school- I had a 4wd Chevy Luv, and you had to be at a "full stop" to switch from 2wd to 4wd, or from 4wd to 4LO. So I'd get up some speed, slam on the brakes, put the clutch in and shift on the fly... had it down pretty good too Was especially useful when it was snowy coming down Berthoud pass or something, I knew by Empire it'd be down to pavement again so last snowy corner I'd rock the 4-to-2 move, so I could drive home in 2wd and not have to stop. Not exactly relevant here, just thought that was a funny memory... I'm going to make sure my son gets a manual transfer case in HS.

 

[Fishy]

I actually started down some of the descents the other night in reverse. There was no question where the traction was, or wasn't. Ice looks like ice, you can't miss it. I also kept 1 foot on the gas, 1 foot on the brake and my hand on the E-brake.

Clearly, this is a last resort and a sketchy technique that claimed MtnAddict's ring gear on the way down. I was more concerned with getting sideways and rolling over with my wife and kids in the truck. I can't stress enough how out of control that ice filled descent was. There was no/none/zero traction on the way down.

Once you get to a certain speed, staying on a tight trail like that was out of the question. If you're on full ice like we were, the reverse/brake/gas/e brake can help you at least stay straight.

 

[60wag]

I don't buy the ebrake thing. If the truck is in 4wd and the center diff is locked, when you apply the ebrake, (rear drums) you effectively brake both the front and rear drive shafts applying braking force to all 4 wheels. On a 2wd car, yeah the ebrake will add drag in the back and might straighten things out a bit but not on a 4wd vehicle.

I missed the the sled run down the icy hill due to the rec' that we not follow. I'm glad that the suggestion was made and that we chose to follow it. I'm undecided on the reverse technique. I can see where it could make the tire claw through some of the packed snow/ice and find a bit of traction that an braked wheel wouldn't. Unfortunately the differentials aren't tough enough to make this a choice without consequences.

 

[mikeyhcrana]

First of all, with my automatic this would not work for me. Even in my 5-speed 4Runner, I would not do that. E-brake is the most effective technique IMO, and it's what saved us. Here's why, I think.

I used to race dirt track modifieds. They don't use much front brake because if your front locks up, you can't steer. On the other hand, you poke the rear brakes, weight transfers forward, and you can steer. Same thing here where it is so slippery, especially going downhill. Slightly setting the E-brake loads the rear brakes so even when you start poking or pumping the brakes, the weight transfers forward without locking the fronts.

Some people say hit this gas when you are sliding downhill. That transfers weight to the back and although you could steer again because the fronts aren't locked, you have to be able to stop the momentum you are gaining soon or the problem is worse. That would have been bad for this Spooky Night Run because nobody knew when they could stop. Probably a good technique for more of a Red Cone situation where all that matters is not sliding off the side.

Going into reverse while moving mimics the correct weight transfer but it's harsh, and out of control. Reverse is for rotating the tires in reverse, you don't want that you just want to use the rear tires to transfer weight to the front without locking the front so you can steer. E-brake does this precisely, predictably and in control. You could even lock the rears and drift down the hills and still be in control because you can steer and modulate the rear handbrake. Maintaining control is priority.

This is my hypothesis, I have no proof, just my opinion. And like the football commercial, it's only weird if it doesn't work. Everybody got the job done that night. In situations like that you can't hesitate and you must trust your instincts, if reverse saved you, I believe you made the right call.

 

[mikeyhcrana]

Was the 4runner who broke doing this, that night?

 

[subzali]

This is why I'm still a fan of chains.

 

[nakman]

Good points Mike. And yeah, it was a 100 not a Runner but yes, I do believe the front diff broke while using this method. We can speculate up and down if that was the root cause, or it was already worn, or it's the weaker 2 pinion known issue design anyway... but alas the load it saw on Saturday night would appear to be the proverbial last straw.

Matt hasn't been mentioned yet, but Seldom Seen was running chains in the back- he said it felt solid the whole way down, almost no wheel slip at all. Think he was about 4 or 5 in line, out of 11.

 

[Fishy]

I would have liked to try the chains. It's something I've considered for my truck (at least having them available to put on). But, I need to run wide spacers in order to make them fit with the 35s. Even with the body lift, I still touch the inner fenders on hard compression.

Josh has the 4 pinion diff, like I did. In this case and in mine when I broke, it wasn't the spider gears but the ring gear that broke. The carrier that the ring gear bolts to deflects/flexes just enough and the pinion jumps and breaks ring gear teeth. I got a good look at mine when I took it apart. Obviously, this may have happened on the reverse descent, or it could have happened during one of the climbs. A spinning wheel that suddenly grabs traction sends a shock load through the system and in this case found a weak link.

I'm convinced that as the 4-pinion type 100's get used/wheeled/worn more, they will break at the same rate as the 2-pinion. The carrier of the ARB or TJM (what I have) is much stronger/ridged than the OEM carrier and doesn't allow for that deflection. Plus, most of the time the person is re-gearing or at least installing new gears at the time of the locker install and more preload is set-up. That also reduces the chance of the pinion and ring gear separating.

You guys who have done this as PM on your 100 did it right. I had to learn the hard way. Nothing motivates learning something new like having to spending money.

 

[Fishy]

Here's a picture of mine.

I think the first break caused some loose teeth to bind again and break a few more spots. Just like in Josh's case, I could still drive and only felt a very slight clunk. It wasn't until I stopped and removed the driveshaft/flanges and spun the tail flange of the diff was I sure of what happened.

 

[AHorseThief]

This is why I'm still a fan of chains.

Agree completely. I don't go winter wheeling without them.

 

[AxleIke]

The action of shifting from forward to reverse with the wheels stopped will no more shock the driveline than reversing normally from a dead stop.

The larger issue here is spinning tires, as fishy pointed out. A few things to keep in mind:

Diffs are stronger in one direction than the other. Depending on your pinion orientation, you may have a stronger diff moving forward, or a stronger diff moving backwards. When you drive on the coast side of the gear, the diff has less resistance to grenading.

Second, with unlocked diffs, you are likely spinning one wheel. Not only is that wheel spinning twice as fast as the ring gear, it is getting 100% of the torque supplied by your front output shaft of your transfercase (assuming center diff locked, or traditional transfercase) where in normal operation, it sees 50%. That is more of a concern for axles, than diffs, but it is a common problem for open diff trucks.

Either way, I think the message is: avoid spinning tires if you can. It is necessary sometimes, but if you can avoid doing it, so much the better. Parts have memory. The more you stress something the more likely it is to fail the next time. By minimizing situations where you are torque loading one side of the diff or the other, the more likely things will hold up when you absolutely have to.

And, body work is usually more expensive than driveline work. Not always, but you can make junkyard driveline parts work more easily than junkyard body parts, unless multi-colored trucks appeal to you

 

[AxleIke]

Agree completely. I don't go winter wheeling without them.

They are good to have, but as with all things, they have situations (like the one above) where they are good, and situations where they are bad (deep snow, snow bashing), where flotation is more important than maximum traction.

 

[AimCOTaco]

I'll definitely agree that anyone who completed the run did great and that chains were king! It really is amazing that there was no real body damage on any of the trucks that descended and that says a lot about everyone's technique and really highlights the fact that there is no one right way to get the job done.

As I read the experiences of guys "pulling a shotshell" I guess I could see a few cases where as a last resort (like a collision, cliff of doom, or insane deep powder) that it could be an option for me.

I still think that a tire rolling in the correct direction is the best way to maintain good steering control which is key for obstacle avoidance in general.

I have not done a lot of winter wheeling the last couple of years but I'm definitely reminded that a good set of quickly deployed chains would have been the safest and most prudent way to approach this descent (another item for my list). This is probably even more the case after other vehicles have polished up the slick spots.

Fishy, speaking of chains, I'm glad you mention the challenges of using them with 35's on the 100. I had never considered chain fit or heard it discussed before with regard to 35's on the 100. I'm trying to keep myself talked out of going down that road for now so this is a great point for me. I like the idea of 35's but I really need to focus on a number of other mods first so anything that keeps me from jumping into 35's is a good thing (at least for now).

As expected this is a great discussion, I love a good tech debate

 

[subzali]

Chain fit is a huge consideration. I don't mind having chains on my 40 because if they rub (which they do) then meh - my tub isn't perfect anyway. But I have hesitated going to larger tires because without more lift the rubbing would be even worse.

Chains on any wagon is going to be difficult. Especially if the bare tire rubs at full compression the way it sits now.