Off-roading Incident/What Happened??

[flintknapper]

Well I spent a good hour and a half last night reading through that thread and others and took away some key lessons:

1. Don’t back up while in a Forward Gear: throw it in neutral or better yet reverse to take advantage of the engine braking. I think my 80 was more forgiving in this scenario as I let it slide down while in forward Gear for a good 10 seconds before I started seeing problems

2. use 2 feet while negotiating a hill, one in the brake and the other on the gas. Keep the brakes on and add throttle as necessary to stay put/go forward

3. Make sure your brakes work and e brakes work. I happened to mess around with the BB pushrod a couple months ago and may have compromised the gasket between the booster and MC leading to a sight vacuum leak in the booster. Didn’t notice or think it was an issue until yesterday . My e brakes weren’t even adjusted so I knew they were no use as I accelerated down.

4. Make sure your brakes and associated components (LSPV and abs module) are purged of all air: didn’t think my brakes were an issue and thought the slightly low/spongy feel was due to me driving sedans all my life but apparently the brakes on the 80s can “throw you through the windshield” if bled correctly. Also noticed the braking performance while backing down a hill is pretty poor, will look into possible mods to improve this...

5. Lock your diffs: I don’t have a CDL switch and the light itself is burnt out so there isn’t a way for me to tell If I was locked or not.

Luke

^^^^^

Very important. If you don't lock your Center Diff....it will act as an 'open' diff. So when/if you lose traction in the front (in a significant way) the vehicle will want to roll backwards...which can initiate the whole 'roll back' issue to begin with. The 'natural' reaction for most will be to give the vehicle more throttle....but because you are in drive and rolling backwards....this can result in a stalled engine.

 

[SNLC]

I happened to roll backwards while forgetting I was still in drive. Is there any fix for that besides knowing better?

Two foot an auto when you off-road it.

Keep it in the correct gear for the terrain-obstacle being driven.

Have a good working ebrake.

Cheers

 

[FirstToy]

 

[flintknapper]

Two foot an auto when you off-road it.

Keep it in the correct gear for the terrain-obstacle being driven.

Have a good working ebrake.

Cheers

^^^^

Yep.

Especially rock crawling or where you face 'steps' in terrain. It helps avoid that throttle 'stabbing' you see so many inexperienced drivers do. Just drives me crazy. 'Smooth' consistent forward motion is usually the answer.

Of course...there are situations that will try even the best off-roader's and I've certainly made my share of mistakes.

Good to discuss those things here.....so all can learn from it.

 

[leonard_nemoy]

Someone in another thread said in their testing, stomping on the brakes once without pumping was better

When your engine stalls, you have limited vacuum remaining in the brake booster. Each time you press on the brakes it uses up some of the vacuum. I wonder if having a small vacuum leak makes this issue much worse. I plan to do my own testing since I want to do Hell's Gate in Moab some day, without dying!

Alright, I need clarification now. I have always been told that you should pump the brakes if your engine stalls or if anything causes your power brakes to go out.

How long would the limited vacuum in the booster last once the motor was stalled?

Right at the end of my last cruisers (91) career it randomly lost power brakes while the engine was running on a very cold morning. A few pumps certainly improved the braking in that situation.

 

[ChaseTruck]

Two foot an auto when you off-road it.

Keep it in the correct gear for the terrain-obstacle being driven.

Have a good working ebrake.

Cheers

Two-foot, for sure.

And I don't know about y'alls trucks, but in all of ours (Toyota or not), the 'e' in 'e-brake' doesn't mean 'emergency'. It clearly stands for 'eventually'. Just sayin'...

 

[WCBlueSky]

Alright, I need clarification now. I have always been told that you should pump the brakes if your engine stalls or if anything causes your power brakes to go out.

I would suggest doing your own real-world testing (in a controlled environment) to see which is better, that is what I'm planning to do, so I'm prepared for an emergency stall on a hill. Also need to tighten my e-brake again, it works but I know it won't hold me on a really steep hill...

 

[mudgudgeon]

Alright, I need clarification now. I have always been told that you should pump the brakes if your engine stalls or if anything causes your power brakes to go out.

How long would the limited vacuum in the booster last once the motor was stalled?

Right at the end of my last cruisers (91) career it randomly lost power brakes while the engine was running on a very cold morning. A few pumps certainly improved the braking in that situation.

I'm my experience you'll get about 2 other pumps before the vacuum is depleted.
Easy to test. Simply apply the brakes in the garage after you have shut off the engine and see how many times you can pump the pedal before the vacuum assistance is depleted.
You'll feel the difference.

Pumping the brakes is only going to help if there's air in the system.
Once you lose vacuum, you need to stand on the brakes a LOT harder.

 

[mudgudgeon]

Reading threads like this, I think I'll stick to manual trans!!

 

[MoJ]

Well I spent a good hour and a half last night reading through that thread and others and took away some key lessons:

1. Don’t back up while in a Forward Gear: throw it in neutral or better yet reverse to take advantage of the engine braking. I think my 80 was more forgiving in this scenario as I let it slide down while in forward Gear for a good 10 seconds before I started seeing problems

2. use 2 feet while negotiating a hill, one in the brake and the other on the gas. Keep the brakes on and add throttle as necessary to stay put/go forward

3. Make sure your brakes work and e brakes work. I happened to mess around with the BB pushrod a couple months ago and may have compromised the gasket between the booster and MC leading to a sight vacuum leak in the booster. Didn’t notice or think it was an issue until yesterday . My e brakes weren’t even adjusted so I knew they were no use as I accelerated down.

4. Make sure your brakes and associated components (LSPV and abs module) are purged of all air: didn’t think my brakes were an issue and thought the slightly low/spongy feel was due to me driving sedans all my life but apparently the brakes on the 80s can “throw you through the windshield” if bled correctly. Also noticed the braking performance while backing down a hill is pretty poor, will look into possible mods to improve this...

5. Lock your diffs: I don’t have a CDL switch and the light itself is burnt out so there isn’t a way for me to tell If I was locked or not.

That’s all I managed to take away before I realized I welcomed in the new year 2021 nose deep in page 10 of that particular MUD thread

if anyone has anything else to offer I am all ears. But if not, thanks to everybody for helping me learn and be a safer driver!

v/r

Luke

Are you certain the CDL light is burnt and that the CDL is actually working?

 

[LandLocked93]

^^^^^

Very important. If you don't lock your Center Diff....it will act as an 'open' diff. So when/if you lose traction in the front (in a significant way) the vehicle will want to roll backwards...

First comment in the thread to help the OP make any sense to me. Couldn't figure out wth was going on.
Sounds like that was the OP's only mistake...not shifting to 4L (which I believe engages the center diff lock on non-diff-lock button trucks).

 

[z531519]

Alright, I need clarification now. I have always been told that you should pump the brakes if your engine stalls or if anything causes your power brakes to go out.

How long would the limited vacuum in the booster last once the motor was stalled?

Right at the end of my last cruisers (91) career it randomly lost power brakes while the engine was running on a very cold morning. A few pumps certainly improved the braking in that situation.

i have about 2-3 pumps before i loose vacuum but you certainly don't want to pump when the engine stalls.

even with a new booster, low-gear reverse or 1st gear, on a really slow crawl on steeps, my brakes would loose a bit of boost as the engine duels with the brakes. I typically end up switching neutral then back in gear, to load up the vacuum (few stabs on throttle), then back to crawling in gear. The engine braking helps build up the vacuum but few times i find i want to go much slower than 1st gear 4-lo (like going down black bear steps).

 

[flintknapper]

First comment in the thread to help the OP make any sense to me. Couldn't figure out wth was going on.
Sounds like that was the OP's only mistake...not shifting to 4L (which I believe engages the center diff lock on non-diff-lock button trucks).

More than one person has discovered this anomaly about the 80 series. Usually in their driveway. IF on an incline you jack up the front end (CDL not locked, parking brake not engaged, rear wheels not chocked, trans in park) you'll quickly find your Cruiser rolling away. Similar situation can occur when off road. CDL LOCKED cures this (open diff roll-back).

Vehicle 'stalling' is another matter.

 

[cog97]

Are you certain the CDL light is burnt and that the CDL is actually working?

After further investigation, I’ve confirmed that the CDL wasn’t activated. The relay itself is bad between pins 6/7, but passed other tests specified in the FSM, so I bought the switch and will be installing that to see if that will do the trick.

 

[cog97]

Reading threads like this, I think I'll stick to manual trans!!

It certainly did make the diesel manual swap look like a more appealing upgrade!

 

[cog97]

More than one person has discovered this anomaly about the 80 series. Usually in their driveway. IF on an incline you jack up the front end (CDL not locked, parking brake not engaged, rear wheels not chocked, trans in park) you'll quickly find your Cruiser rolling away. Similar situation can occur when off road. CDL LOCKED cures this (open diff roll-back).

Vehicle 'stalling' is another matter.

In my case and in the case of the video @WCBlueSky provided, I believe my rolling backwards while in forward gear caused the engine to stall via the torque converter. In my particular case, I don’t think locking the center diff would have made a difference. I quite literally backed the car up on all 4 wheels while forgetting it was still in drive for a good 10 seconds before I noticed something was amiss.

In the Moab video it looked like the 4 runner accelerated back down cowboy hill quite rapidly while still in drive. Unlike me: I backed down with my foot on the brake while in drive, which is what delayed the stall.

 

[cog97]

First comment in the thread to help the OP make any sense to me. Couldn't figure out wth was going on.
Sounds like that was the OP's only mistake...not shifting to 4L (which I believe engages the center diff lock on non-diff-lock button trucks).

Apologies, ill try to clarify it in the original post:

I was in 4lo, only problem is my CDL relay pin6/7 lost its continuity (bad diode: I confirmed this after the fact).
So I was in low but without the center diff locked. I just bought the switch and will be installing that soon to see if the relay can successfully talk to the actuator motor.

 

[leonard_nemoy]

but you certainly don't want to pump when the engine stalls.

Okay, hypothetical question. You get back from a week long backpacking trip and your parked at the top of a mountain. Your battery is dead and you can't get a jump start so you decide to coast down the canyon with no power brakes. Would pumping the pedal help as you attempt to slowly coast down the canyon?

 

[mudgudgeon]

Okay, hypothetical question. You get back from a week long backpacking trip and your parked at the top of a mountain. Your battery is dead and you can't get a jump start so you decide to coast down the canyon with no power brakes. Would pumping the pedal help as you attempt to slowly coast down the canyon?

No. The only time pumping the pedal is of benefit is if you have air in the brake lines. Pumping the pedal a few times allows you to compress the air a little.
I would not recommend coasting far at all with no engine power. Its doable, but steering and braking with a dead engine is hard work. Easy to balls it up.

 

[leonard_nemoy]

No. The only time pumping the pedal is of benefit is if you have air in the brake lines. Pumping the pedal a few times allows you to compress the air a little.
I would not recommend coasting far at all with no engine power. Its doable, but steering and braking with a dead engine is hard work. Easy to balls it up.

I am still confused, I clearly remember learning in drivers ed, in the 2 week driving class fed ex put me through, the three week driving class that Snap on required, and reading in the handbook for my CDL that you should pump your brakes if you lose braking.

Here is a link that also says the same thing.

Handling Brake Failure | How To Handle Brake Failure - https://www.idrivesafely.com/driving-resources/how-to/brake-failure/

And another

Brake Failure - DriversEd.com - https://driversed.com/driving-information/defensive-driving/brake-failure.aspx

I certainly believe what you guys are saying but I just want to be sure so others are not misinformed.