Cruise Control Downshift

I will start this thread by saying that I hate the radar cruise control and only ever use the manual cruise. Haha.

I have a 2019 SR5 CM 4.6L 4x2. When driving on the interstate with the cruise set (usually 70-75 mph), the truck downshifts to go over even the slightest incline. I’m in south Louisiana so the highest elevation change is the overpasses. Every vehicle I have ever owned just stays in the same gear while applying more throttle for a few seconds to maintain speed.

Is this just a Tundra thing or should I have the dealer take a look at it?

Thanks,
DP

 

Smaller engine with a heavy tires/truck...your transmission is trying to keep up...I think it's common...My V8 4Runner does the same and tho it's annoying, it's common and nothing to fret over as far as the truck not behaving normally...perhaps look into OVTuning for their updated flashes for the engine and transmission...that would help what you're facing...though, I'm not sure there are many tuners for the 4.6...

 

I guess it’s more aggravating than anything. I’m a bit hesitant to do a ECU flash because it’s still under warranty.

 

Gotcha...yeah, I'd wait a bit and get to know your truck and all the pros and cons and then figure out what matters most to you on where you throw your money...

 

Try doing 80 it might not do it as much LOL

 

How do you use “manual” cruise versus “radar” cruise. I find myself with cruise set at 70 on interstate. Get driving and without realizing it, I’m behind a car and slowed down to 65. Found it makes me less alert as a driver.

 

You could also try going slower and putting it in fifth. Also what you might be hearing is the torque converter unlock instead of an actual downshift.

 

It’s better on the engine and transmission to downshift and get closer to the power band than to lug along with a less power and more throttle.

 

My sentiments exactly. I typically use sequential so I could be right where I want the truck RPMs in the power.

 

Instead of pressing the cruise control button in one time to turn on radar cruise, hold it in for about 3 seconds. You’ll see the cruise control light in dash change from the radar cruise symbol.

 

I’m so happy I can rear end people now!!!

 

I’m with you on the radar cruise making me feel less alert. I am not a fan...

 

With the oxygen thieves we have driving down here, I can rear end them with the radar turned on.

 

Do you have evidence to support that? I've debated with myself if more rpm and less throttle or more throttle less rpm is better for the engine. It seems to me less rpm would always be a happier engine, even if it's loaded up more.

 

I love the radar cruiser control, as my wife says she knows when it's on because I never use the brakes LOL

 

https://lmgtfy.com/?q=why+lugging+an+engine+is+bad

Driving at full throttle with the engine at a low RPM because the transmission is in too high a gear is known as lugging your engine. ... At the most basic level, lugging your engine doesn't make much sense because it puts your engine at a disadvantage. That means it has to work harder to do the same amount of work

 

That's dope you can copy and paste text from the internet that explains literally nothing. Was hoping for a simple explanation why it's bad besides "iTs BaD aNd ThAtS bAd", especially since most articles and videos don't seem relative in the context of the Tundra.

 

The link provided has plenty of sources explaining why lugging the engine is bad for you I even filled out the search engine for you (Shrugs) I'm not trying to be a smart A$$

The Tundra engine and tranny are not something all that different, even if it was a rotary engine.. The gears in a transmission work just like other gears it makes the job easier, so lugging in a high gear you are making the engine work harder.

 

This video explains "engines"
https://www.youtube.com/watch?v=soJea7xEt-8

 

It is a happy medium of powerband efficiency, rpm, and torque. Really lugging a motor (e.g., high gear, max throttle, and low speed) puts a lot of heat into the system and loads the bearings heavily with minimum oil flow. Bad for engine. You will frequently hear spark knock due to high combustion chamber temps when doing this. OTOH, running 40 mph at 4000rpm is not good for mileage or long term use of the engine either. My truck shows about 400 rpm change from 5 to 6th. No big deal. I try to keep the torque converted locked for lower trans temps by using sport mode.

 

Yea I agree the engine is working harder, but is that necessarily a bad thing? The broad overviews of lugging say that the engine is working harder and that's more heat, etc. But on the flip side, if the engine is compensating for that (adjusting timing accordingly) or just plain isn't getting too hot, or the engine isn't actually "lugging", then is it a big deal? Some forum discussions state lugging as under 1500rpm and full throttle.

So my question is, with my OVTune I can lock into 6th gear. Driving home up the mountain before the tune the truck would drop into 6th or even 3rd gear to maintain 80mph on the interstate. With it locked into 6th gear it can maintain that same 80mph by giving it more throttle, is the engine less efficient and not making peak power? Yes, but it can still handle and even accelerate fine. The engine isn't pinging, the coolant and tranny aren't getting too hot, the thing is running at like 2300rpm. I wouldn't call that lugging. Point being, everyone in this thread is acting like if you give it full throttle cruising the interstate and it doesn't downshift into 3rd that the engine will blow up. So my question I was hoping to answer is it bad for our trucks to be locked into a high gear and given full throttle? This isn't full throttle at 900rpm or something, this is giving it more throttle at 2200+ rpm and with a modern advanced ECU. So what's the issue? That video and nothing I've read addresses that. Everything talks about if you're truly "lugging" it, like a manual trying to launch from barely rolling in 6th gear which is not the case for us, and furthermore why I think the cruise control on the trucks is retarded and downshifts when it shouldn't be and would be fine if you lock it into a higher gear.

 

Watch the video it explains and answers your questions. No your engine is going to blow up but your could be damaging it to a future failure. I believe this video does answer your question