[nvrsmr08]

Hey guys,

I have a 07 Sport with approx. 80,000 miles. For a while now my truck has been downshifting and up shifting sporadically at lower MPH (15-50 mph). My question is what sensors are directly related to giving the computer the information to up shift or downshift?

 

[mr.reaper2]

Hey guys,

I have a 07 Sport with approx. 80,000 miles. For a while now my truck has been downshifting and up shifting sporadically at lower MPH (15-50 mph). My question is what sensors are directly related to giving the computer the information to up shift or downshift?

Obviously automatic....
Vehicle speed sensor,
Throttle position sensor,
Engine speed sensor.

Edit: What do you mean by "sporadically"?

 

[nvrsmr08]

While driving at around 35-45 mph or sometimes slower / faster when I let off the throttle it likes to downshift like it would if I was going downhill. So it seems that the computer is getting weird readings when I let off the throttle, or the hill decent feature is acting up? I have a AFE stage 2 intake and the rest is stock.

 

[mr.reaper2]

While driving at around 35-45 mph or sometimes slower / faster when I let off the throttle it likes to downshift like it would if I was going downhill. So it seems that the computer is getting weird readings when I let off the throttle, or the hill decent feature is acting up? I have a AFE stage 2 intake and the rest is stock.

From what I've heard... that's normal. The ECU on the Automatics have engine breaking programmed in, so it will downshift in order to slow you down. You need to keep on the throttle in order to "coast".

Remember that this is a throttle-by-wire system, so squeezing down on the giddy-up lever slightly, doesn't necessarily cause the throttle gate to open.

Edit: That's also a 2007... I understand that there is a new ECU program (alters shifting/throttle patterns) since then. Have you had the new program installed on your ECU?

 

[nvrsmr08]

I am 100% sure that what it is doing is not normal. It also happens when I am slightly on the throttle. How hard is it to replace these sensors? I have taken the truck in and the dealer would not do the re-flash because my truck is a 07.

 

[05Moose]

From what I've heard... that's normal. The ECU on the Automatics have engine breaking programmed in, so it will downshift in order to slow you down. You need to keep on the throttle in order to "coast".

Not sure that's what is being described. Yes, they don't just coast. But they also don't downshift unless you actually press on the brake pedal. So it does require human responses to trigger the downshifting for engine braking.

 

[05Moose]

I am 100% sure that what it is doing is not normal. It also happens when I am slightly on the throttle. How hard is it to replace these sensors? I have taken the truck in and the dealer would not do the re-flash because my truck is a 07.

Dealer will do the reflash because it's part of a recall (the one where they chop the gas pedal and reflash the ECU for the brake override function). Have you already had that recall done?

 

[mr.reaper2]

Not sure that's what is being described. Yes, they don't just coast. But they also don't downshift unless you actually press on the brake pedal. So it does require human responses to trigger the downshifting for engine braking.

Wonder if the brake light switch is stuck?

OP: go check if your brake lights are working correctly!
BTW: I'm 99.9% certain that changing any of those sensors will NOT help you. If they were bad, there would be more obvious symptoms, like throttle lurching, speedometer or odometer bouncing around like a retard, etc.

 

[nvrsmr08]

I have had the gas pedal recall. I just checked and my brake lights are working fine. I am not sure what is causing it but this is starting to bug me more and more. So changing the sensors won't help at all?

 

[mr.reaper2]

I have had the gas pedal recall. I just checked and my brake lights are working fine. I am not sure what is causing it but this is starting to bug me more and more. So changing the sensors won't help at all?

Most likely not.
You could try doing a fluid flush... Make sure that you use the right kind of ATF.

 

[nvrsmr08]

Did my fluid flush about 5000 miles ago. Used Toyota Fluid. It was doing it before I did the flush.

 

[mr.reaper2]

Did my fluid flush about 5000 miles ago. Used Toyota Fluid. It was doing it before I did the flush.

Damn. You got me then.
This is basically why I opted for a manual.....

 

[nvrsmr08]

Just went and took the kids to the store. Even during normal driving foot on throttle lightly, it will act like it is confused whether or not to downshift or stay in 5th gear????

 

[05Moose]

Just went and took the kids to the store. Even during normal driving foot on throttle lightly, it will act like it is confused whether or not to downshift or stay in 5th gear????

Next time you think it's in 4th, shift it manually into 4 and see if it the RPMs stay the same. I'd like to know for sure if it really is downshifting or not and that will tell us for sure.

Just some other info to jot down. What speed are you going when it's happening (exact speed rather than a range, and slight or moderate downhill slope?), what RPM before and after you feel it doing this, and what's the RPM when you manually downshift to 4?

If it truly is downshifting, you'll see the RPMs rise. If you're simply feeling the engine resistance when it cuts off the fuel, your RPMs should stay fixed (not climb up unless the vehicle speed slowly increases and in those cases the RPMs will rise similarly with the engine speed).

 

[nvrsmr08]

Alright I will check on that stuff tomorrow and get back to you. I dont think my RPM's move which is why I am a little confused. I feel it want to down shift or try to but not engage??

 

[05Moose]

If the RPMs are not increasing, then it isn't downshifting. In which case, you're probably feeling the truck holding back which is normal. And in the low to mid 40 MPH range, if you're on level ground or a slight incline then you'll feel it trying to decide which gear to be in. And it might also be locking/unlocking the torque converter. I've got a road nearby where mine does that. In those situations, it's much smoother to manually leave it in 4th.

 

[nvrsmr08]

So this is normal, and I shouldn't worry? I believe it is the torque converter going in and out, if so is there a way to smooth the transition?

 

[mr.reaper2]

So this is normal, and I shouldn't worry? I believe it is the torque converter going in and out, if so is there a way to smooth the transition?

Heh heh, normal... isn't that what I said?

The torque converter has a lockup clutch, its electrically operated by a solenoid. It is possible that this clutch may be worn, causing it to engage excessively harsh. It is hard to say if this is the case or not through your subjective description. It may be perfectly fine, or it may be engaging funny.

This is also a common problem that can be caused by using the wrong transmission fluid. I do note that you said you used Toyota ATF. Do you know that Toyota uses multiple different kinds of ATF? Specifically, which kind did you use? You didn't happen to use a type T, T-II, T-III, or T-IV, did you? I believe that the proper fluid for this transmission is type WS.

http://freepdfhosting.com/cd481dc8ae.pdf

 

[Splicer]

I believe that the proper fluid for this transmission is type WS.

Yes, it is. :thumbsup:

 

[nvrsmr08]

I used the WS fluid and the place used the BG machine, I believe it was all done correctly I watched them to make sure.