Shifting down when using cruise control

I have a 2016 TRD Sport with a 3in lift and 17in TRD wheels. When I'm driving on flat roads on the freeway at speeds greater than 77mph the truck will stay in 5th gear (about 2,500 RPMs) using my foot on the throttle. However, when I engage the cruise control it always shifts down into 4th and the RPMs jump to 3,500.

I have tested this when traveling on no-incline (or decline) in the road. I have tested with and without ECT power. The truck is in 2WD, and it is not windy. I don't have TOW haul.

Any thoughts on why the cruise won't stay in 5th and always shifts down, but without the cruise control on I can keep it in 5th?

 

Thank you. I'll try the TSB update and see if that helps. Hopefully it does, because going on any long highway trips sucks when you're at 3,500 rpm the whole way.

 

Not doubting the accuracy of the conditions you report but this doesn't sound right. If you're on relatively flat roads with normal wind without towing or a heavy load (could be cargo or people) going to and staying in 6th and at worse case 5th should be routine. My truck will shift to 6th and lock the converter at speeds over 45-50 mph which produces about 1200`1500 rpm. Of course if I goose the gas a bit it will proceed down to 5th, and if I really climb on the throttle I might see 4th. Get the latest TSB as that's got to be the culprit.

As to why you see a quicker down shift from CC vs your own foot on the peddle, I believe it's the behavior of the cruse programming. While in CC if you lose speed for any reason other than your foot on the brake, CC will attempt to compensate by applying more throttle and it does it pretty radically in an attempt to go back to the set speed quickly. While when you're in control of the throttle, you are probably less aggressive in trying to get back to speed... Anyways that's my theory.

 

Try lowering the speed to 65mph and see if it holds gear better. Anything over 70mph at maintaining speed with cruise control on these bricks, especially with a 3 inch lift is a struggle.

 

Well I’m going to get the update today and see if that helps.

Ive really tried to remove as many variables as possible. I’ve maintained a speed of 78 for about 45sec (one mile) and the truck stayed in 5th (2,500rpm). I then turn on the cruise control and as soon as it engages the truck down shifts. It just doesn’t make sense. I get that it’s fairly boxy with the 3” lift, but I don’t know why the cruise would make it shift down when it can easily maintain that speed in the higher gear.

Anything lower than 75 the cruise seems to do just fine. I’m in Utah and I drive to Idaho to see family. Speed limit is 80 on the freeways, so maybe I’m an outlier and Tacoma’s just don’t run well above 75?

I’m really hoping the update will fix it. Fingers crossed.

 

The truck shifts where it needs to be. You might notice a lot of pedal pressure doing it yourself. Bad for MPG too. I use cruise here in the Carolina hills and easily get 18-20 mpg all the time with it. Just let it shift and don't worry about it.

The TSB will not fix it.

G.

 

I just got back from the dealer after they installed the TSB updates. I went on a test drive and everything is working great. The truck now easily stays in 5th after the cruise control is engaged at higher speeds and on flat roads.

Thanks for all advice and help. Much appreciated.

 

Give it awhile.

G.

 

It will go back....sorry
I’ve had the TSB done and still suffer the same issues. It’s just par for the course
With these trucks. 75-85 with the CC on just won’t shift unless it starts a decline.
I’ve resigned to just not take it on long trips.

 

This is the TSB that finally made my wife stop commenting about sluggishness. She didn’t know I had it done and noticed on her own.

 

I had the TSB done recently and I am experiencing a new issue. When using cruise on a hilly road doing approximately 50 mph, my truck will shift down to what maybe 2nd gear (4000 rpm).....going down hill. It did this several times. Had to turn it off. Works fine at 65 on the highway. No ECT and I tried it in both S and D modes. No difference.

 

Cruise control WILL shift down to try and maintain your speed with engine braking. Depends on how much “down hill”.

G.

 

engine braking to maintain your set cruise speed. going downhill, the truck is speeding up, the cruise is doing it's job, and drops a gear to slow you down to the selected speed. it wont "coast", then recover your speed when you are no longer on a hill.

 

Yeah...that makes sense. However, the action is very aggressive. Make you jump on the wheel wondering wtf is going on aggressive.

Thanks.

 

Sorry to dig up an old thread — I am betting I’m on the same route you were when you wrote this— salt lake to driggs Idaho going 80mph. I’ve got a scan guage measuring temps and was surprised to see the same 3300’rpms for 80mph minor hill freeway travel. What concerned me is that even though other posts say this is normal, the trans temps hold steady around 195 and climb as high as 205 if you keep on 3300 rpm range—- I’m pretty sure my fluid is in ballpark bc temps are steady otherwise but I guess I’m not sure I buy that running a truck in 3k rpm w 200+ trans temps is a good thing. Love the truck (2020 Trd off road long bed) but man those high rpms make me nervous

 

Dave,
Don't sweat it. The truck is doing exactly what it is designed to do. Don't try to out-think the engineers. Yes!! this truck is way different than what most people are used to.

G.

 

Besides holding a higher rpm longer than it seems like it should, it floors it to gain 3mph rather than gradually increasing. I get about 1-2mpg better easily if I’m not using cruise ...

 

Little known fact - you can even shift the manual with cruise control on and it won't cancel. Only vehicle I've had that does this.

 

If you are in S mode if you shift below 4th it will cancel cruise. You can lock it in 4, 5 or 6 and cruise works fine. In fact, if you are cruising along at 70 and want a boost you can shift to S which puts the tranny in 4th and step on it. Works well for passing on a two lane.

 

This is on I84 outside of Boise, not abnormally windy. I'm on 33s. The truck wants to stay in 4th gear at 5k+ rpm until I blip the throttle. Then it shifts down to 5th and 6th momentarily until shifting back to screaming.

This isn't normal, the truck can clearly maintain speed in 5th and 6th. I don't have any of the TSBs, my shop isn't interested in doing it.

https://youtu.be/LPjulm_sNmM