Truck rolls backwards in Drive......why? (1 Viewer)

[loop737]

My driveway is sloped, yesterday I performed a little test, with the truck in D I took my foot off the brake, the thing will roll down a hill until you add gas. When you add gas it makes the hideous noises as the hill start assist kicks in. I've never owned an automatic transmission that behaves this way. If i do the same thing in my LX470 the truck stays put, no rolling. I know this is normal behavior, I'm just wondering if anyone here knows why it was designed this way. It's a 2015 LX.

Thanks

 

[ElJayBird]

Mine does the same thing and it’s really annoying. Hill assist seems broken to me. I had hill assist in my Mercedes and it wouldn’t budge when I took my foot off the brake.

 

[loop737]

Mine does the same thing and it’s really annoying. Hill assist seems broken to me. I had hill assist in my Mercedes and it wouldn’t budge when I took my foot off the brake.

I agree, and why would you need hill assist with an automatic trans? With a normal auto. isn't hill assist built in? ha ha. I've got a 5speed manual Taco, and on that hill assist is useful. This deal is just odd, and yes....annoying.

 

[Cmab]

Is the noise like a big spring releasing and hitting your floorboard with a clunk and the spring vibrating? That is how mine sounds and actually makes the same sound at times when I’m cornering uphill at speed over a bumpy road. Anyone know what’s going on here?

 

[ElJayBird]

Is the noise like a big spring releasing and hitting your floorboard with a clunk and the spring vibrating?

Yes - that’s it

 

[chilibit]

Since you have it in Drive the system thinks you want to go forward. Sensors say you are rolling back. So the braking system is correcting the condition. They could dial up the transmission's creep and it would be awful in traffic. They could install one of the many systems that KEEPS you from rolling back. BUT, there are many off road situations where I want to drop back slightly and I do not want to make a shift. I am too precariously balanced. So I think Toyota made a trade off and I think it has merit. Spend a lot of time in 4Low on bad terrain and you could learn to love the springy sounds. There is also that hand brake thing.

 

[rscoleman]

Have a 1997 T100 4x4 with 5 speed manual hill assist is brain telling left foot to just start slow releasing of clutch right foot move from brake to gas all in seamless dance while trying to not roll backwards into the idiot who is tailgating me.
Good luck figuring out if you have an issue. I have not really noticed the behavior in my 2016 LC. I quite often pull a boat from boat launch did so just this past Sunday. I get tiny roll back from boat launch with 3500lb out back end but not more than inch or two which could just be suspension.

 

[speyrod]

Mine does the rollback with no noise and it bugs the poo out of me. The noise would make it worse.

 

[ElJayBird]

LOL - these apologist explanations remind me of when the iPhone had an antenna problem and Steve Jobs’ response was “you’re just holding it wrong”. Psshhht...get real

Seriously though, if hill assist isn’t broken in my Land Cruiser then it’s horribly designed. Period. There shouldn’t be some esoteric operation...it should work by simply taking your foot off of the brake while on a hill and then disengaging when you apply pressure to the accelerator.

 

[JtFSU]

LOL - these apologist explanations remind me of when the iPhone had an antenna problem and Steve Jobs’ response was “you’re just holding it wrong”. Psshhht...get real

Seriously though, if hill assist isn’t broken in my Land Cruiser then it’s horribly designed. Period. There shouldn’t be some esoteric operation...it should work by simply taking your foot off of the brake while on a hill and then disengaging when you apply pressure to the accelerator.

Yes! My 2016 GMC Sierra worked like a charm. When on incline, or I’m sure at all times, brake pressure held until the gas was pushed, or about 2 seconds, which ever happened first.

This is one of the bigger of my very small gripes about my LC. For all the other tech it has, a smooth Hill Assist should be one of them.

I did try the other day to really put pressure on the brake on a hill, and it seemed like it held more like it should, but only once. Haven’t been able to repeat even at the very same spot.

 

[loop737]

My owners manual states, “Do not let the vehicle roll backwards when the shift lever is in a driving position”. Well isn’t this exactly what hill start assist is supposed to prevent? The whole thing just seems stupid. If there’s an off-road situation where you need to roll backwards why not Nuetral or reverse? Again, my 06 LX doesn’t do this. And mine will also roll downhill without noise, just like it’s in nuetral, until you add gas.

 

[TeCKis300]

I'll say buck up and learn the car.

It comes down to how the torque converter is calibrated, specifically the stall speed.

Some cars are setup with a lot stall engagement at idle. Tundra for example. It wants to jerk and go as soon you put it in drive. Which means it's already transferring significant torque into the driveline, so it'll hold the car at idle on a hill.

The LC is setup with more manners and doesn't put much torque to the wheels at idle. It's also a relatively heavy vehicle as we all know so its propensity to slide rearward on an uphill is greater.

That said, I know the later model years on the LX did get Hill Start Assist where a firm press on the brake pedal will activate the brakes to hold the car from rolling back for 2 seconds. Likely the LC got it too.

 

[Markuson]

My driveway is sloped, yesterday I performed a little test, with the truck in D I took my foot off the brake, the thing will roll down a hill until you add gas. When you add gas it makes the hideous noises as the hill start assist kicks in. I've never owned an automatic transmission that behaves this way. If i do the same thing in my LX470 the truck stays put, no rolling. I know this is normal behavior, I'm just wondering if anyone here knows why it was designed this way. It's a 2015 LX.

Thanks

I believe hill assist is only designed to stay active for a brief moment after releasing the brake pedal.

After that, it assumes you want to control your vehicle’s power and braking yourself.

 

[ElJayBird]

I'll say buck up and learn the car

I have. It doesn’t have hill assist.

 

[loop737]

Soon after I bought the truck I was sitting in the driveway waiting on the garage door, once it opened took my foot off the brake to pull it in and backwards we went. Obviously yes, this can be dealt with rather easily, handbrake etc. But the previous generation didn't advertise the electronic nanny known as "hill assist" and yet, stays put on hills. This one advertises hill assist, and rolls all over the place. So if it wasn't broke, why'd they try to fix it?

 

[Hoosier Daddy]

I've had numerous other Toyota 4x4s with Hill Assist, and would agree that the 200 is by far the least aggressive of the bunch. The 200 requires much more backward movement to trigger and has much less force in braking than the others. But no big deal, since I don't rely on it.

 

[TeCKis300]

I can imagine delicate situations off-road where when moving between forward and reverse, that I don't want the torque converter to load up and surge the vehicle even an inch. Or hitching up a trailer and trying to inch the ball under the hitch.

A high torque motor like the 5.7L, with sufficiently low gearing in low range, would buck and surge when I don't want it to. So perhaps the ability to hold on a grade is the compromise that I'm okay with. For those that have driven a Tundra with the same 5.7L, it has pronounced load up where it can even chirp the tires.

How did we ever drive manual cars if we can't manage a little roll in an auto car?

Here's Hill Start-Assist on a 2016 LX.

 

[tabraha]

Sounds like many are not activating the hill start assist properly? Are you mashing the pedal hard to getting the chime/dash notification?

 

[Ruquik]

I'll say buck up and learn the car.

It comes down to how the torque converter is calibrated, specifically the stall speed.

Some cars are setup with a lot stall engagement at idle. Tundra for example. It wants to jerk and go as soon you put it in drive. Which means it's already transferring significant torque into the driveline, so it'll hold the car at idle on a hill.

The LC is setup with more manners and doesn't put much torque to the wheels at idle. It's also a relatively heavy vehicle as we all know so its propensity to slide rearward on an uphill is greater.

That said, I know the later model years on the LX did get Hill Start Assist where a firm press on the brake pedal will activate the brakes to hold the car from rolling back for 2 seconds. Likely the LC got it too.

Who are you and how do you know about how a torque converter actually works. As someone in the industry i was surprised to see your comment amongst this group.

That being saide by 13's reactor is far far too tight imho. Barely come off the brake at a red light or have the AC com on and you are into the car in front of you. Honestly though about cutting the converter apart and throwing the reactor on the lathe and raising stall a couple hundred rpm. Might actually make the CRAWL control in the lowest speed way less jerky too.

 

[TeCKis300]

I'm not in this particular industry, but have been accused of being a gear head more than once.

It's funny what's too tight for one, others might find too loose. A quality that gives a car character for some is a flaw for another. There's certainly a bit of preference and black magic to it all. Sometimes it is what it is because of design and engineering compromises.

EV's have the ability to completely get rid of many of the vehicular compromises like this one, on account of the internal combustion engine. While I also have an EV, I'm deathly afraid the future is going to be too sterile. Heck, there may be little to no more actual driving soon. So I'm more than happy to learn and adapt to my vehicles. The more raw and engaging, especially manual cars, the better.