Truck downshifts when applying brakes downhill

I don't have DHA. Yet when I apply brakes going downhill, the truck will downshift. Why? Can I disable it?

 

Downhill assist?

What you are experiencing is what every vehicle does when slowing down.

 

Because you are slowing down.

 

Welcome to TW by the way. PS, your caps lock is on...

 

Welcome to TW!

 

Welcome to TW.


Uh...why would you not want it to downshift when slowing on a down grade?

 

This seems to be a Toyota thing. I’ve never driven any other vehicles that downshift on hills as soon as you hit the brake. But I driven several different Toyota models and they all seem to do it in one form or another.

 

Slowing down to a stop vs just tapping the brake cause you are running up on someone a little fast are different things. I’d want it to downshift at the shift points. But for whatever reason, the Toyota automatics downshift as soon as you touch the brake.

 

Ok, but I'm still not understanding why that's not desirable.

With my crazy ass, I'd rather it downshift early than late. When at max payload or tow it really doesn't take much to heat the brakes and get the dreaded pad fade. I've been in situations where I went from 70 to zero on a perfectly reasonable yet downhill highway exit, and I knew my fronts were soft by the time I reached the light. If the transmission can take just a little of that burden, it's safer for me. Not for the first stop, but the 2nd, 3rd or 5th stop that happens after I've already put some heat into the wheels.

So even when adjusting my space in moving traffic, I'd rather have downshift.

 

It’s because you are on the brake and the ECM cuts fuel.
This doesn’t always happen, and it’s speed dependent (along with other stuff)

@nd4spdbh explained it once. But I can’t find that post.

 

Welcome to TW. Safety first!!

 

It’s just a preference thing I guess. I personally think it’s weird especially since it seems to be more common on Toyota’s than other vehicles. On long hills I want to do max coasting even if I occasionally need the brake. The thing that is annoying to me about it is that once you let off the brake it won’t upshift until you accelerate a bit. Getting back to the gas just a little bit isn’t enough to make it want to upshift. You need to measurably increase your speed then back of the pedal before it will upshift. I find this whole procedure annoying to have to do repeatedly on long hills.

Either way the point is moot for me now. I swapped my truck to a manual. Now I can row the gears when I want.

 

If you were actually using DAC you'd be off road on a steep incline in 4Low (with the tranny shifted into low gear) and you wouldn't have your foot on the brake... DAC does the braking. As far as the truck downshifting on a hill that's exactly what you want it to do.... it's called engine braking.

 

Huh… guess my Taco is an oddball then; it does nothing like this. Acts like any other car with an automatic that I’ve ever owned. I do manual downshifts when appropriate and it always results in higher revs, so it’s never beating me to the punch. At least, not until I press on the accelerator again.

 

Welcome to TacomaWorld

 

Yes, this is normal. AI control. Apparently to help a little with brake wear according to the Car Care Nut. One of the first things my wife noticed when she first drove the truck and thought it was awesome, “very truck like” she beamed. Loaded and traveling through steep mountain grades I use S-mode regularly for engine braking going down and to keep RPMs up while climbing. Works very well.

 

DHA and the downshifting while braking continuous down a slope are two different things.

Down Hill Assist is only on 09+ TRD OR 4x4's and keeps the vehicle at 5mph or under without touching the brakes when activated.

The downshifting you are seeing under normal street driving is due to the transmission AI and is 100% normal. The trans AI keeps an eye on loads in and out of the transmission and things like if you are on the brakes or not and if you are going up or downhill. It will downshift and hold a gear longer than normal outside of standard transmission tune nothing going uphill under power and downhill for obvious reasons.

You can bypass the AI downshift(s) on a downhill one gear at a time back up to 5th if you move the shifter from D to 4 back to D.

You can bypass the AI downshift(s) on a downhill all the way straight to 5th without fuel cut (coasting) by going D to N back to D

 

Normal. Does it only on very steep downhills after a firm press on the brakes. Then you don't need to keep riding the brakes to more or less maintain a steady speed. Will up shift as soon as you apply some gas.

 

My 07 has DAC...

 

I should of clarified, 09+ standard on TRD OR 4x4's. 05-08 TRD OR 4x4 was optional with the VSC package (a rare option btw) which it looks like you have.