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Overdrive dropping out occationally
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g00se
Novice
Jun 6, 2023, 2:45 AM
Post #1 of 13
(1868 views)
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Overdrive dropping out occationally
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Hi,
I've imported a 2001 petrol Japanese Toyota Hiace into the UK. It's in very good condition for it's age, 100k miles.
The transmission is a A45DL - which I understand is called a hydraulic transmission. There are no diagnostics available - the only electrical connection is really the overdrive solenoid switch.
It drives fine apart from occasionally dropping out of overdrive and back again. I've taken it to a transmission shop and they dropped the pan and changed the fluid for me. The fluid had started going a light brown but still red in there and hardly any deposits on the pan magnet. The guy was happy with the condition - but said that old transmissions may drop overdrive occasionally. It hasn't got any better or worse since the fluid change.
It's hard to identify exactly the situation this dropout happens but usually it's after running the vehicle in stop start traffic for a good while and then hitting the motorway - no real load in the vehicle, 1 driver, 1 passenger. The overdrive will drop out for a few seconds before jumping back in. Sometimes once, sometimes a couple of times in close succession (20-30 second gap between). Once it lasted for about 15 seconds before cutting back in. The speeds this happens are around 55-70 mph. Once it's had it's little fit, it will keep running at motorway speeds for hours without a problem. But it has done it once when just warmed up, but with a six passengers. And once when decelerating to a junction (from about 50mph - just one passenger).
The temperature gauge is always sitting just below middle - though these vehicles' temp gauges have a reputation of sitting in the middle until it jumps into the red.
The O/D off light and switch seem to work fine. The light does NOT come on when the overdrive drops out. Flicking the switch on and off does not help when it has dropped out.
The vehicle electrics are fairly simple. I haven't had the dash off, but the specs I can find suggest the O/D off switch connects to a relay - which connects to the O/D solenoid. It's possible there is an ECU rather than the relay, but again, it would be a very simple ECU. It's OBD1 and not OBD2, but the engine diagnostics it does have are clear. There was an exhaust lambda sensor that had failed, which I replaced - but that made no difference to the problem.
Any suggestions as to what it may be? I'm hoping it may be the solenoid, or a transient overheating issue (the coolant circuit is shared with the engine, with not additional cooling to the transmission). Any suggested tests?
Many thanks in advance,
G
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jun 6, 2023, 3:42 AM
Post #2 of 13
(1856 views)
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Re: Overdrive dropping out occationally
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G,
Hold tight this site has a transmission specialist stops in when he can. This isn't sold to the US where we are centered with the best of info on it but trans # and miles listed helps. His name is Gary (gsferraro) so just hold on, Tom
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gsferraro
Veteran
Jun 6, 2023, 5:00 PM
Post #3 of 13
(1814 views)
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Re: Overdrive dropping out occationally
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Hello, this is a rear wheel drive car? is the overdrive solenoid on the outside of the trans or inside on the valvebody? Gary
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gsferraro
Veteran
Jun 7, 2023, 4:01 AM
Post #5 of 13
(1770 views)
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Re: Overdrive dropping out occationally
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Hello, This is old school, If i remember, as a test we used to take the inner o-ring out of the solenoid, when this is done you cannot cancel overdrive it should always have 4th, so we can tell if the solenoid was bad or not, we use to do this in the 80's, you could try that as a test or even unplug the solenoid and see what happens. That solenoid should be the overdrive cancel solenoid. Do you have a scan tool that shows live data? Gary
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g00se
Novice
Jun 7, 2023, 6:20 AM
Post #6 of 13
(1757 views)
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Re: Overdrive dropping out occationally
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I've got a basic OBD2 bluetooth scanner - but there are no diagnostics with the transmission. The only electric connections as far as I can tell are the OD solenoid and possibly the kick down. There's an old Toyota OBD1 port, but the transmission pins are missing (which I assume is beause there are none). The diesel versions of the van have electronics, but the petrols use the old transmission for some reason.
I'll try disconnecting the solenoid to see if that works - thanks for the suggestion.
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gsferraro
Veteran
Jun 7, 2023, 7:27 AM
Post #7 of 13
(1752 views)
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Re: Overdrive dropping out occationally
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Let me know. Gary
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g00se
Novice
Jun 7, 2023, 8:01 AM
Post #8 of 13
(1746 views)
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Re: Overdrive dropping out occationally
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Will do - I won't be in a position to test it for about two weeks but I'll let you know how it goes. Thanks again for the help
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g00se
Novice
Jun 28, 2023, 12:37 AM
Post #9 of 13
(1623 views)
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Re: Overdrive dropping out occationally
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Hi again,
I haven't had a chance to do this yet, as the van has developed another issue with the engine (starting when hot). I'm replacing the distributor and rotor as they're shot - but I think the viscous fan is suspect too - and causing heating issues. These vans' temp gauges have a reputation of sitting in the middle until they jump into the red - so they can look like running normally unless it's catastrophically hot. So do you think a hot transmission could cause this problem? It only seems to happen after sitting is slow traffic for a while - which would tie in with the fan not pulling air properly.
(This post was edited by g00se on Jun 28, 2023, 12:42 AM)
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Hammer Time
Ultimate Carjunky
/ Moderator
Jun 28, 2023, 3:36 AM
Post #10 of 13
(1606 views)
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Re: Overdrive dropping out occationally
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Please keep to one subject per question. The overheating is something for a different question in a different category.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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g00se
Novice
Jul 23, 2023, 1:30 PM
Post #11 of 13
(1472 views)
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Re: Overdrive dropping out occationally
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Hi - I've got it solved while looking into the overheating issue (I know, bear with me please). It's old and has OBD1 diagnostics but I got hold of an old reader to monitor the engine temp - and noticed that the temp sensor for the ECU would very occasionally drop to -20C for a few seconds. This was usually while warming up and it would subsequently run fine when warm. But would also happen when it was cooling down from being a little overheated - for example - trying to start the engine after it had been sitting for 30 minutes, or from going from stationary traffic to a fast road (the situation where I was getting the OD dropping out).
In the electrical diagram, most of these era vehicles have the overdrive solenoid controlled by the overdrive off switch and the ECU (if the engine is cold, it stops the overdrive kicking in - I understand it's so the engine warms up faster at higher revs). For my gasoline version, I've only found a spec which has the transmission OD solenoid the O/D off switch only.
But after replacing the temp sensor - I've not seen the OD drop out yet - so I'm thinking the ECU is involved in my version of the van. The sensor notifies the ECU it's well below freezing and the ECU cuts the OD - until it's warm again a few seconds later. I didn't get a chance to monitor the sensor temperature when this happened previously so can't be sure - but I've driven it long enough now without it happening to think it's fixed.
Thanks all
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 23, 2023, 2:09 PM
Post #12 of 13
(1465 views)
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Re: Overdrive dropping out occationally
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Thanks for your reply of your solution.
BS from here not my intention just happened,
Be well, Tom
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Hammer Time
Ultimate Carjunky
/ Moderator
Jul 23, 2023, 2:14 PM
Post #13 of 13
(1462 views)
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Re: Overdrive dropping out occationally
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OK, closed now as solved.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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