High Transmission Temp Warning - Stalling in 4lo

This. Any time you manage to stall an auto, the high temp warning will come on till restart, despite temps being Normal.

 

I think we could all dream up 100's of nightmare scenarios where the loss of momentum/traction/split second of power brake loss could be detrimental, and I agree its probably not a huge deal most times it happens, especially if you're aware that it might. I'm more interested in the duplication; what causes it? Two foot driving seems to be the consensus, but is it degree of incline, 2wd/4wd, # of RPM's, brake pressure, or any other factor that can be measured to find the root of the problem? I can definitely modify driving habits for a quick fix, and tell my wife not to 2 foot it at the boat ramp, but at the end of the day, there's reasons we all felt the need to use 2 feet, and its preferred in many cases.

 

The new Chevys do something similar but it disengages 4x4 as well, which seems pretty ironic on the ZR2s...

https://www.caranddriver.com/features/a39850302/chevy-silverado-zr2-4wd-off-mystery/

 

Happy I found this thread. Had this very thing happen to me going up Imogene from Ouray several weeks ago. I picked the wrong line and got off camber on a steep incline near the top. Truck stalled out, I think every light on the dash lit up at once. Was able to roll back down enough to get more level and after a minute or so, the truck started and we kept on up. No issues since, glad its not just my truck but more my choice of lines lol

 

It's not a two foot thing, it's just a roll back thing. Most vehicles with auto trans will do this. People who two foot are deliberately trying to avoid roll back which is common in offroading, when you are in an awkward climb. Lower crawl ratios reduce the need to two foot.

 

yea its the nature of the game unless you have a dedicated rig to just crawl with that is geared ridiculously low and dual cases etc. Most of us probably drive there and back so our rigs arnt set up like one that is trailer'ed. Im convinced by the evidence that it has nothing to do with the 4wd system and just a safty feature of the transmission. As i stated i have non of the factory 4wd stuff on my truck and i have an FJ cruiser tcase and my truck still did it.

 

Maybe I misunderstood; it sounded like 2 footing to the avoid rollback is what was making the CPU unhappy and causing the stall, which made sense. I don't see why rollback would cause stall; seems like thats when hill-assist/god awful grinding brake sounds would kick in, as designed. Brake and throttle input at the same time makes more sense, and is what I thought you were referring to originally.

 

i think its more so related to a load on the transmission on a rollback as apposed to just a roll back as iv rolled back on some hills on road that are not that steep and nothing has happened.

 

I can replicate rolling backwards in drive on an incline, and not stalling. Thats actually how I discovered my truck had the "hill-assist" feature. Once I figured out those god awful sounds were just the ABS working to keep me from rolling back, I tested it again to see how far it'd let me roll back. My conclusion was, too far for my comfort, and too much crawl control type noise that makes me uneasy to continue with that test. All in all, the truck never stalled when I allowed it to roll backwards down an incline in drive; the hill-assist just kicks in. The only way to get out is to give throttle input (put load on trans), while the truck is auto braking, so in theory, if you were right, this should replicate the issue every time, but it doesn't.

But lets assume you're right; pulling a boat out of water, or ascending an obstacle on trail, puts plenty of load on the trans, and you should understand where someone would be concerned about their truck stalling while performing that task. Whats the solution? Two foot to avoid rollback? Bc that seems to be the only common factor for everyone that has reported this. With the only given reports in this thread, I'm led to believe it has everything to do with brake pedal input, in conjunction with throttle input, with 'probably' some other factor we haven't figured out yet.

That article about the zr2 points to this conclusion as well and proves it to be the fault in other vehicles.

 

I think what your missing is the load in the reverse position which your only going to get if your on an incline severe enough say 40-50* ish. Have you stalled on a boat ramp before? Your indication if i read that correct that you cant replicate it but the ingredients just aren't there from what it sounds like. I don't ever see a scenario where you'd have a trailer hooked up on that extreme of and angle. I will also say the times it has h append to me my truck was also bouncing as well so that may have a factor as well.

 

Thanks Joe.

Fortunately, it never happened when I was in a hard place. If I did, I would sure hate not having power assist at help.

You said that you can replicate it. Can you describe how? Or is it more of an in the moment I know what happened kinda deal? I have 5.29s so two footing is not always needed...

 

Find a large obstacle, ledge, or steep climb etc that really requires the vehicle to pull itself up. During a climb you typically apply variable pressure on the skinny pedal to adjust for speed and climbing dynamics, too much lift and the vehicle will fall/roll back. The vehicle will either stall on roll back or when power is immediately applied during the roll back.

We go to Moab every year and over a week of wheeling I probably stall on a ledge once or twice during each trip. I don't do it on purpose but I can duplicate over and over when place in the same situation.

 

If I recall VSC, TRAC etc are all disabled in 4-lo so no hill-assist in those situations. 4-lo creates too muhc torque for a road incline to test, you need a ledge or something.

As far a ssolutions, yup it just comes to driving experience, either two foot it or apply constant throttle pressure to maintain forward movement.

A fun saying we use, when in doubt throttle out.

 

I've never experienced it. I'm trying to figure out from the ones that have WHY they experienced it. You don't ever see a scenario where someone would have a trailer hooked up on an extreme angle, yet I'm telling you a boat on a steep ramp in the water is the perfect example. It meets all the criteria you say need to be there to replicate this issue. Why should someone not be concerned about finding a cause/solution to that problem?

So can we confirm that this issue is limited to 4wd only? Brian says otherwise, but I don't count his experience towards any of this since he's 2nd gen and DIY 4wd converted.

 

I don't think it's limited to 4wd as it's related to the transmission not the transfercase. However, its likely significantly harder to reproduce in 2wd because of the situations (e.g. offroad climbing) needed to duplicate.

imho a boat ramp isnt steep enough but i havent ever launched a boat, typical environments that I have had it occur is climbing 12-30" vertical (or almost) ledges/rocks. Or climbing 30-40 degree inclines.

 

Curiosity had me thinking if it were an issue of gas/brake pedal depressed simultaneously, others who've attempted burnouts have probably reported the same error codes/stalls. To my suspicions, TW threads seem to suggest this is true, so I'm sold on that as the culprit. I still think the real question, is how much of each pedal is "too much", or what is the other factor possibly needed to simulate a stall?

 

I think the fact that mine isnt a factory setup makes it more proof its not 4wd related because if it were 4wd computer related then why would i be experiancing it and i dont have any of that? Like @JoeCOVA said above "
I don't think it's limited to 4wd as it's related to the transmission not the transfercase. However, its likely significantly harder to reproduce in 2wd because of the situations (e.g. offroad climbing) needed to duplicate.

imho a boat ramp isnt steep enough, typical environments that I have had it occur is climbing 12-30" vertical (or almost) ledges/rocks. Or climbing 30-40 degree inclines." this is the recipe.

 

I never thought it was 4wd specific; I'm only asking questions and using each of your points against the other, because ya'll are claiming the same things, with opposing information. I think doing this kind of deductive reasoning eliminates the "I think it is ____" and points to the actual facts. The whole boat ramp thing is irrelevant at this point; I'm not trying to argue about boat ramps steeper than any you've experienced existing; only trying to get to the root of the issues, and ensure it doesn't happen in an inopportune time (whether that be my wife at a boat ramp, or me climbing 50 degree ledges).

 

like what i think we are saying the same thing sometimes stuff gets lost over the internet.

 

Fair enough, honestly the big thing is just being aware of it. I can see how the first time would be somewhat alarming, especially when you dont know why. As familiar with it as I am, it's unavoidable in some situations and you just restart the truck and keep going.