Hungry Valley trip and the things I learned

[Devil's Slide Doug]

Just to beat a dead horse. I do not understand why the engine would stall if he was not rolling backwards. As far as braking is concerned, the cdl switch would seem to be pretty important. I would nor want the chance of abs deactivating my brakes and how much difference would the lspv make with the cdl locked? Both axles will be traveling at the same speed. Also the ebrake should affect the front wheels via driveshafts and locked transfer case tied to the rear wheels.
Totally off the topic, an auto is a much different beast than a manual. I will admit that I am much more comfortable with my manual tranny pickup as I always know that it is in gear, especially in a stall situation(even though this happens more frequently). I hate the fact that an auto is "freewheeling" when the motor is not running. One other peeve is that I can shift a manual tranny by feel quickly (it is instinctual) but have to look at the shifter to know whether I have shifted an auto into a particular gear or not. Auto's give me a real sense of lack of control (or disconnect if you will).

 

[NLXTACY]

Its not beating a dead horse if the issue hasn't been solved yet.

 

[Chaldaean]

I do not understand why the engine would stall if he was not rolling backwards.

douglashuft, I was rolling forwards with the transmission in Reverse; essentially rolling backwards.

 

[george_tlc]

Well, good to hear that other folk have now observed this stalling when in gear and the vehicle rolls in a direction opposite to that gear's working direction. Like I wrote early on in this thread, I just figured it was a stupid automatic 'thing' and to deal with it by not letting it do that. Of course in the heat of the moment it could get a bit 'tricky'. Googling shows a few other folk observing or noting this quirk - one on a tacoma forum. Wonder if this is more a toyota thing or a general auto thing.

Seems like this quirk should have been brought up a long time ago. Being as the 80 was my first auto 4wd I found this issue quickly, since being use to a manual and having the need to roll backwards sometimes in a forward gear I was use to just pushing in the clutch and letting the vehicle roll (like out of a driveway) without the need to get into reverse and back into 1st. So, with the auto I figured on a steep driveway since it would start to roll even in drive (high range obviously) to let it roll - that's when I noticed the stalling issue. Just figured that was par for the course with an auto and learned to just put it in R to back out.

I presume what we are seeing is sufficient load on the engine to stall it out. One would think the ECU would try to maintain idle speed to prevent the stall, but either it is more than it can handle or the load happens quickly after the auto is run 'backwards' for some distance. No idea how an auto deals with running backwards, but maybe there is a fairly rapid pressure buildup in all those slipping bands and junk and something inside 'locks up' quickly and that sudden load change stalls the engine.

cheers,
george.

 

[Devil's Slide Doug]

douglashuft, I was rolling forwards with the transmission in Reverse; essentially rolling backwards.

I was referring to NLXTACY's stall where he was essentially moving forward in a forward gear when he stalled. Even if his cdl was off and the transfer was allowing an entire axle to "differentiate" or slip, the transmission output would still be moving in a "forward direction". Transmission and motor and drivetrain all essentially moving the same direction.
The only way I see the truck stalling in that situation aside from an engine issue is if the slipping axle suddenly got traction and the low idling engine with a locked torque converter stalled (as it might with a manual tranny)
The brakes I write off as a not running big heavy truck on a steep incline with possibly a tired booster and possibly abs gone awry.

 

[CreeperSleeper]

I have found a solution!!! When wheeling, use your left foot to brake. This way the brakes will be on if your engine stalls in this maner. It works for me... Never been out of control while braking... I've been out of control a couple times at WOT, but never braking. Engine running or not.

 

[e9999]

well, I have to take back what I said earlier.

I went out and was able to stall the engine in both directions on a slope of about 10o.
That was both in High + D and High + R.
ABS on I imagine, CDL unlocked.

The e-brake could easily stop the truck, though, and when stalled I could stop it with the pedal too (easily without lifting my foot and pushing hard after pumping a few times.) Steering was hard but sort of manageable.

The engine didn't stall right away, only after hiccuping a few times over a distance of about 50-100'. (Probably cuz I was in H.)

My LSPV has been reset for my lift.

Altogether, this is really good to know.

 

[Devil's Slide Doug]

That's terrific, everywhere you look you see cruisers on steep hills stalling as we "test" our vehicles. Yes I am guilty of this too, It did take several car lengths in high range rolling the opposite direction of the gear I was in and I did feel the pressure build in the tranny. My brakes still worked as did my parking brake. What is different of course from the scenario that started this thread is that I intentionally allowed my vehicle to roll back while in a forward gear compared to the vehicle simply stalling while essentially just driving forward. Obviously, NLXTACY has some sort of engine issue to work out.

 

[NLXTACY]

Obviously, NLXTACY has some sort of engine issue to work out.

What makes you think its an engine issue?

Something else is definitely going on, no doubt.

 

[e9999]

the thing that is really important about this, though, is that it is critical to put it in reverse if you lose traction on a steep slope going up and need to go back down. This is somewhat counterintuitive, of course, since many folks would probably think that they will go faster back down in R than in D or N. (And indeed it might, given that the wheels could still spin forward in D while you go back, which would exert an opposite force, not that that would be good for control...)
One of those things that one would probably do wrong based on one's instincts in the heat of the moment...



But again, for clarification, I never had my engine stall while going up or staying stationary on a slope. It is, however, entirely possible that I went back some short distances for repositioning while still being in D. If it happened at all, it would be unusual, though.. And didn't stall then either.

Also, when my engine stalled in this test yesterday, it was pretty obvious something weird was afoot. The truck hiccuped, lurched, and generally misbehaved for quite a distance and time before the engine actually stalled. (May be faster in L though.)

 

[latinoguy]

well, I have to take back what I said earlier.

I went out and was able to stall the engine in both directions on a slope of about 10o.
That was both in High + D and High + R.
ABS on I imagine, CDL unlocked.

So you are saying that you also managed to stall the engine in Reverse as well?

 

[e9999]

So you are saying that you also managed to stall the engine in Reverse as well?

it stalled while going backwards (by gravity) facing upwards while in D
and also
while going forward (by gravity) facing downward while in R

 

[Sporin]

interesting. One of the reasons I went back to an automatic rig was to avoid the butt-puckering stalls in tough terrain. My FJ62 was great for that, never stalled, no matter what angle. For a family wheeler, it takes a lot of the drama out of challenging obstacles.

As long as brakes still work and it restarts it's no big deal, I don't think, but in the OP's case, no brakes is the scariest issue.

 

[NLXTACY]

Seems every time I tried to find time to replicate all the theories offered, I keep getting sidelined. I still want to find the time to do this to finally put this to bed. As an aside, I've driven 600 miles round trip to Vegas and then the round trip to San Diego with zero issues. Of course I'm always flat driving to those locations

 

[Nottajeep]

I had this issue happen while wheel n up a steep slope in m 97 LC this past weekend. Kind of embarrassing in front of a bunch of jeep owners. Basically, I replicated the original posted issue. While driving up a very steep slope and losing traction just before climbing the top, I let off the skinny and momentum carried me backward(while in 4LO). Upon reaching the 20-30 ft bottom, engine stalled.

 

[greentruck]

Interesting reading this old thread. The 80 is my first auto 4x4, also. I'm going to be careful out there when I get the truck in the mountains. Glad I'll have the benefit of everyone's experience to consider.

One more factor about the need to get the truck in R when rolling backward...to get R on the auto tranny, you have to push the tranny lever FORWARD, instead of pulling it back as in a manual trans. This is especially counter-intuitive if you're used to driving a manual, even if you've finely tuned your reflexes to fight the urge to simply brake backwards instead.

Just one more factor among many, I know, but one that it also pays to consider before you head up Pucker Hill

 

[e9999]

So, NLX, does that mean no Lion's Back for you then?

 

[80t0ylc]

Interesting reading this old thread. The 80 is my first auto 4x4, also. I'm going to be careful out there when I get the truck in the mountains. Glad I'll have the benefit of everyone's experience to consider.

One more factor about the need to get the truck in R when rolling backward...to get R on the auto tranny, you have to push the tranny lever FORWARD, instead of pulling it back as in a manual trans. This is especially counter-intuitive if you're used to driving a manual, even if you've finely tuned your reflexes to fight the urge to simply brake backwards instead.

Just one more factor among many, I know, but one that it also pays to consider before you head up Pucker Hill

With the recent rise in interest of rock crawling, hill climbing is becoming a lost art, IMHO. For me, it used to be one of the biggest thrills and challenges in off roading. And as many, I suspect, new to off roading on this forum are finding out, there are unique skills and challenges to master to avoid disaster.

Negotiating a steep hill requires some cautions that need to be thought about in the driver's head before you get on the slope. You need to know ahead of time just what your plan of attack is going to be if you loose momentum and can't continue. Because, in the "heat of the battle", the novice's reflexes can get them in big trouble. To try and keep this post to a reasonable length, let me state my 3 basic rules, with a brief and simple explanation. They are related, so to simplify, here's the 3rd rule first:

3. When traveling side hill, avoid as much as possible, steering up hill. If you must go in the up hill direction, first slow the rig to a crawl. A quick explanation to that is that traveling on a side hill, if you turn up hill, you will be fighting both gravity and the normal centrifugal force to keep your rig from rolling.

1. First rule applies to both transmission types. If you loose forward momentum attempting to climb a steep hill, the very first thing that you do is get the rig in reverse. You want as much braking power as possible working for you, engine compression and brakes.

2. This is next thing that should be on your mind after getting rig in reverse. Keep the rig straight as possible as you are backing down the hill. To try and manuver left or right, with any speed, would cause you to fall victim of the forces described in rule 3.

These rules or considerations have worked for me for 40+ years of off roading with street legal vehicles. Hill climb competitions are a whole different world, but fun to watch. I'd probably never even attempt some of those monsters. I'm no expert - just trying to help fellow mudders with less experience than myself.

PS: 1 last rule - Always crest the top of a hill with caution if you don't know what's on the other side.

 

[Nottajeep]

All good points... I am learning more each time I go out. In talking with my local cruiser shop, my engine stalls are crap fuel related (according to them). Next wheeling expedition, I will upgrade to premium and shell v power if available. I might also burn some injector cleaner to clean out the tank with any foreign debris that may be lurking in the tank. Bottom line though, I am surprised of the roll back. How do these crawlers avoid this situation. 2 feet driving?

 

[hawaiicruz]

check out post #186