Tranny upshifting and downshifting randomly
10-20-2010, 09:55 AM
#21
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My A340H (3VZE auto) does the same thing intermittently and up until recently, had no obvious causes. It has become more frequent over the last few years and I just recently noticed that it's beginning to react to the throttle position occasionally. If it starts downshifting/upshifting between 3rd/4th and I let of the throttle just a hair, it stays in 4th. This is not always the case but seems to be consistent enough to be related. I haven't tested the TPS yet but am fairly certain it is the culprit and will post my findings hopefully tonight.
10-21-2010, 04:54 AM
#22
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We own a 1989 toyota camry with 200,000 hard miles and it has a similar issue as you are having with your 4runner. Driving at any speed, fast or slow, it will sometimes shift from o/d to 3rd iradically and vice versa. Sometimes we can be driving it with no troubles at all. It will shift and stay in o/d for the duration of the trip. Other times it is annoying and will stay in 3rd. The car has no RPM gauge so we feel as if we have to go 45 or less when it shifts down to 3rd because the ole girl sounds like shes revving way up there.
A few years back we replaced the ECU and ECM (if i remember correctly) because that is what the transmission tech. told us to do. It did nothing. We flushed the tranny, too. He couldn't figure it out after that and we really didn't want to spend any more money on an old unsafe beater. My cousin, who's a GM mechanic, thought it to be a shift solenoid. He doesn't want to mess with a *Toyota* though. She still runs great around town though, just not a highway driver.
Anyway, I just thought I would throw that out there. I know it's not the same vehicle and maybe even not the same problem. But I will keep following this and see if you figure it out because this is interesting.
A few years back we replaced the ECU and ECM (if i remember correctly) because that is what the transmission tech. told us to do. It did nothing. We flushed the tranny, too. He couldn't figure it out after that and we really didn't want to spend any more money on an old unsafe beater. My cousin, who's a GM mechanic, thought it to be a shift solenoid. He doesn't want to mess with a *Toyota* though. She still runs great around town though, just not a highway driver.
Anyway, I just thought I would throw that out there. I know it's not the same vehicle and maybe even not the same problem. But I will keep following this and see if you figure it out because this is interesting.
Regarding my problem, my truck is without an engine, so I havent been able to check anything else yet. One I get a new engine in, Ill let you guys know how it ends up.
10-21-2010, 05:30 AM
#23
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My A340H (3VZE auto) does the same thing intermittently and up until recently, had no obvious causes. It has become more frequent over the last few years and I just recently noticed that it's beginning to react to the throttle position occasionally. If it starts downshifting/upshifting between 3rd/4th and I let of the throttle just a hair, it stays in 4th. This is not always the case but seems to be consistent enough to be related. I haven't tested the TPS yet but am fairly certain it is the culprit and will post my findings hopefully tonight.
10-21-2010, 07:32 AM
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Although it does sounds like the same problem, I'm also noticing my Torque Converter locking and unlocking up. You should see a 300-400rpm change at around 40+mph. If you have that same problem, then welcome to the club! If not, you're lucky! 3rd/4th gear misshifting probably is a bad solenoid that can't hold up once pressure rises up. Try getting your valve body and solenoids checked.
Ya the torque converter locks/unlocks too. I'm pretty convinced it's strictly electrical though, eigher the TPS or ECT sensor. Didn't get a chance to look at it last night but I'll post my findings when I do.
10-21-2010, 03:08 PM
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Looks like this is a common problem with no solution. I've been having the same issues, shifts irradically an won't shift into o/d. Seems like every time i hit a bump it jumps down or up. O/D didn't work when i got her, so i took it to my local trans mech. He replaced the valve body an checked all the solenoids and they all checked out. Strangely it worked fine for about 6 months and then started acting up. I'm leaning toward the thermo sensor being the culprit. Gonna take it to a guy that specializes in elec. problems to pinpoint the problem. I will post what i find out.
03-03-2013, 04:23 PM
#30
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I think I am on to something.. The tranny speed sensor is not reading..weak magnet I assume. I ordered a new one..waiting for it to arrive to install. The magnets go bad with age..80s vintage. Will let you know how shifting goes when installed.
03-12-2013, 07:21 AM
#31
Thats what i was going to say. I have the same problem and again just sometimes but i have code 61 #2 speed sensor or bad wireing and that could be the case with the wireing so bad on a 90 model from the heat of the tranny and the cross over exhaust.
03-13-2013, 04:35 PM
#33
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My transmission diagnostics are giving me a code for #1 and #2 speed sensors 42 and 61 tested both sensors...In cluster and on Tranny..replaced tranny sensor with new one..getting correct signals from both (0 to infinity ohms) next check wiring..possibly a bad ground or splice somewhere. Ordered another ECT computer to troubleshoot. Tranny shifts fine with light throttle..adjusted TPS to specs. Can any body confirm correct TPS part # for an 86 4Runner? Why would i be getting codes for both speed sensors? is there a possible ground common to both? does the Tranny ECU case have to be grounded? The troubleshooting continues. Need some tranny experts on this forum!!! Lol. The Local tranny shops here don't have a clue!!
Last edited by milowilli; 03-13-2013 at 04:44 PM.
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