2023 Badlands dangerous unintended acceleration while in four-wheel-drive low

[jon]

Have you ever had a four wheel drive vehicle before

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[Charles Miller]

Have you ever had a four wheel drive vehicle before

Yes. I had a Four-wheel-drive Toyota Tundra.

 

[jon]

Yes. I had a Four-wheel-drive Toyota Tundra.

I meant an older four wheel drive vehicle, like an old Jeep or something with a transfer case. Meaning depending experience with manual inputs and drivelines working with synced and not synchromesh gearing, chain transfer cases versus gear transfer cases etc. There are a lot odd noises and conditions you can get a four wheel drive vehicle into that could cause jerking. After reading other folks comments it sounds like what you are experiencing is more than just drive train differences and sounds more like computer control of RPM/drivetrain mode.
I would love to get my hands on the complex algorithms that go into controlling the engine drivetrain and see what is really happening under the hood. There is probably a reason for this and it may be to counteract something else. One thing I would hope to sacrifice is smooth ride so that engine does not die when in an extreme obstacle.
As an engineer I never consider any feedback as wrong, because if someone's perception is that something is wrong then there may be a better way of accomplishing the task. If the engine is surging is to prevent a stall, or surges in order to increase torque so that suppling enough power for all parts of the drivetrain ensures overcoming a rock etc, the unintended consequence may be a small surge. I don't know the reason but would love to learn!

 

[BodieMonster]

I just had this happen to me on the trail over the weekend as well. I was descending in 4L (sway bar disconnected but no GOAT modes), so I put it in 1st via Manual Mode but the section was not so slow I needed to crawl down so I shifted up to 2nd for a bit (while coasting so foot off the gas), and then when I changed to 3rd it lurched as the RPM's jumped (maybe to around 4k). This happened twice more and think one of the times may have happened from 1st to 2nd as well but I can't quite remember which gears I was between.

 

[Hemisfear]

I have noticed in 4L only and not ROCK CRAWL, that if you downshift while in auto the motor will rev to match rpm's I assume and will accelerate, I thought this was normal.
I would call this "inexperience" rather than "sudden acceleration"! lol

 

[telenerd]

4low seems a little wonky on the shift points. I had same problem where the bronco sorta lurched forward while applying the brake going over some rocks. I then shifted to manual mode and didn’t happen on trail. So I guess this could be a gearing or programming issue? 3 gear seems a bit too tall compared to 1 & 2nd.

 

[telenerd]

So I did some more trail running today. When your in 4 low in auto mode the up shifting from 2nd to 3 is smooth. But if you’re going down hill or around a small bend on the trail you have to watch your rpm and speed when it down shifts to 2nd. If you’re at 2k rpm in 3rd and then slow down, the Bronco automatically shifts down and it will lurch forward and spike up the rpm. If you’re going super slow around 5mph and the RPM is 1500k the down shifting is smooth from 3rd to 2nd.

So I guess the moral of the story is when the trail is tight or you’re going down hill stick it in manual mode when in 4low. I didn’t have any issues in manual mode.

My guess the spread between the gears takes some time to get use to for the 4.7 gears. A programming change might fix things down the road.

 

[7sKnuckledragger]

No offense guys but are you aware of crawl ratios?
The bronco has a really great transfer case, compounded with 4.7 axle ratios and your crawl ratio goes way up. Near where my jeep is (4.56 gears with a 4.32 Atlas transfer case, in first gear on flat ground I can stand on the breaks and the gears overpower the break system).
in 4L just a slight increase in RPM if sudden can cause significant lurching.

 

[Bronco1971]

I just experienced a similar condition. But this was in 4L and at a complete stop in D while easing brake pressure. Only in normal mode, did not do in in mud/ruts. Once at a nose down attitude, once on level ground, third was at at a fairly steep upward angle. Only lasted for maybe two heartbeats.

 

[mrjking2000]

ok i experienced this just yesterday on a trail. downshift from 3rd to 2nd and i almost rammed the vehicle in front of me. i was slowing down to stop, and when it went from 3rd to 2nd holy moly hang on! i have called my dealer to report this as this is extremely dangrous behavior. think about making a turn on a switchback and you need to 3 point turn. it downshifts to 2nd and you have to STAND on the brake pedal. but instead, over the cliff you go.

 

[vicorjh]

I've had this occur while in 4A. Had to stand on the brakes. Not really a lurch per se since I was moving slow and coming to a stop. Just a bunch of torque with no gas pedal applied. It was a surprise.

Thankfully, so far, this has only occurred once.

 

[ScLeCo]

When off road in 4L you should never be so close to the vehicle in front of you, that no matter what kind of sudden lurch, you would even come close to hitting.

With that said.

 

[mike8675309]

I’m so confused, are you are on an off road trail or driving on the road? If your on the road why are you in 4Lo? Yes the car accelerates differently when in 4Lo because the gearing is very different than 2 or 4Hi. As stated 4Lo is for off-road use only.

He was offroad in a caravan of others driving offroad

During the off-rodeo, I was in a Badlands and it did surge in 4L, and like the OP, I do know features and what is normal.... I talked to the instructor and it wasn't normal, and that he had felt it too driving the Bronco I had. No idea why Badlands would be different, it did have Sas, so the 4.46 (??) gearing wasn't in play. It should be the same power train as my Wildtrak.

I had the auto during the off roadeo and I always had it in M1 or M2 but for one fast section when I put it into 2wd. This was in New Hampshire. I recommend if want to go more than 8 or so mph, take it out of low range. Or get a manual transmission. The higher the transmission gear, the harder a bronco would be to stop if it's in a low range.

 

[OK_Hunter]

I experienced the same thing coming down cinnamon pass this past Friday...4L driving slowly downhill and the upshift gives a hard lurch forward. Manual mode keeps it under control but you better be aware of where you are on the trail of you're in auto.

 

[3People1Body]

My take on it (now), it's normal. Last month in Moab, it was doing it quite often (mainly going downhill?). I wasn't using manual, hindsight I should have.

It's hard to anticipate, unless your off-roading a lot. I still love my Bronco, and drive it for what it was intended.

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