On the highway at really any highway speeds say 55-80, it will downshift up a hill like it should but rarely upshifts afterwards. Hit cancel on the stalk and it immediately upshifts. What would cause this?
80 Series Transmission rarely upshifts with cruise on.
- Thread starter thetoyotaman
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Normal function of a Cruise control system that's 30 years old.
The downshift is a combination of throttle position, speed sensor, and the ECU throwing the solenoids in the transmission.
The upshift is exactly the same, but with the CC on, the upshift can be very delayed depending on the situation.
On my LX450 it will upshift well after I crest a hill and the throttle has been backed off for a while.
Yes, it takes some time and can be annoying.
How long ago was the fluid replaced?
- Thread starter
- #4
I just changed it.
Same performance here. It can be a little unsettling to see and hear the engine revving like mad well after any sane human would have backed off and let it rest a bit, so I just cancel Cruise Control and it immediately goes back to a sane gear choice and RPM. If there aren't more hills coming, I set CC again and let it do its thing.
Honestly, this happens so rarely around my AO (Sonoran Desert) that I barely even think about it anymore, it's become second nature. In a hilly area, I'd probably just turn CC off and drive it the old fashioned way,
Honestly, this happens so rarely around my AO (Sonoran Desert) that I barely even think about it anymore, it's become second nature. In a hilly area, I'd probably just turn CC off and drive it the old fashioned way,
I agree. Also, this is both electrical and mechanical, I wonder if adjustment of that cruise control throttle cable might make a difference.
My cc has been operating that way for years. When I’m in Hill country, I just drive without the cc.
When this happens, if you accelerate to 5 to 10 miles an hour over the set speed and it still does not upshift, to me that would mean electrical. Above the set speed the cc is relying on data to shift, if I’m not mistaken.
I’m looking at it this way. If the transmission works fine the rest of the time when it’s not on the cc, then it has to be something relating to the cc. The transmission is under control of the cc when it is on and is relying on the data supplied by the TPS and the speed. Maybe one of those inputs is at fault.
I call that analog driving.
From the Toyota FSM:
"When driving uphill under cruise control, in order to reduce shifting due to ON−OFF overdrive operation and
to provide smooth driving, when down shifting in the electronically controlled transmission occurs, a signal
to prevent upshift until the end of the up hill slope is sent from the cruise control ECU to the electronically
controlled transmission.
Terminal ECT of the cruise control ECU detects the shift change signal (output to electronically controlled
transmission No. 2 solenoid) from the ECM.
If vehicle speed down, also when terminal ECT of the cruise control ECU receives down shifting signal, it
sends a signal from terminal OD to ECM to cut overdrive until the end of the uphill slope, and the gear shifts
are reduced and gear shift points in the electronically controlled transmission are changed."
Note the highlighted text. It's holding 3rd gear on purpose.
"When driving uphill under cruise control, in order to reduce shifting due to ON−OFF overdrive operation and
to provide smooth driving, when down shifting in the electronically controlled transmission occurs, a signal
to prevent upshift until the end of the up hill slope is sent from the cruise control ECU to the electronically
controlled transmission.
Terminal ECT of the cruise control ECU detects the shift change signal (output to electronically controlled
transmission No. 2 solenoid) from the ECM.
If vehicle speed down, also when terminal ECT of the cruise control ECU receives down shifting signal, it
sends a signal from terminal OD to ECM to cut overdrive until the end of the uphill slope, and the gear shifts
are reduced and gear shift points in the electronically controlled transmission are changed."
Note the highlighted text. It's holding 3rd gear on purpose.
"changed" or "flushed"? The former is useless; the latter is what you want to do.
- Thread starter
- #12
When I did the engine about 30k ago, I put the torque converter flat on a 5 gallon bucket and drained as much as I could and stood the trans up as well. As I recall I captured about 9 quarts or more. I cleaned the pan, the screen and put new neo magnets in it so 30k later I drained the gallon or so that came out and added new fluid. It seems happy except for this issue.
- Thread starter
- #13
Has anyone replaced all the items on this thread and was able to fix the problem?
In the future, I'd suggest flushing, as it's not only much easier, it also carries some solids out with the fluid, which wouldn't necessarily happen with a gravity drain.
As to your shifting problem, I can't help. Knock on wood, I've never had this happen to me.
- Thread starter
- #15
That requires a machine I think. I'd be a little nervous that might block a passage if there is any debris in the system with my 330k
What items are you referring to?
CC is hanging on to 3rd gear because it's supposed to.
- Thread starter
- #17
Tranny solenoids, speed sensor, and throttle position sensor
If any of those were an issue, the transmission wouldn't shift properly without CC.
You would also have error codes.
- Thread starter
- #19
I ordered a new throttle position sensor. My current one passes the FSM test criteria but I am seeing erratic readings driving different speeds. I read that it may be bad but pass the test ok.
- Thread starter
- #20
With the new TPS, once truck tops a hill a slight input of the accelerator causes it to upshift now.