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Problem-86 Toyota Truck Automatic Transmission Overdrive
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bob_...@my-deja.com
Jul 31, 2000, 3:00:00 AM7/31/00
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I have a 1986 1-Ton Toyota truck with a mini-camper body and 32,000
miles. After driving for several hours on level roads at 50 to 60mph it
no longer wants to shift into overdrive. The hydraulic circuit of the
overdrive mode on the A43D transmission is electrically controlled. I
have bypassed the electrical control elements and have applied 12 volts
directly to the O/D control solenoid so I can manually control the
solenoid. It works fine when it has been driven for less than an hour.
But it still has the same problem of not shifting into overdrive when it
reaches its maximum operating temperature. There does not appear to be
a thermo-switch on the vehicle that would inhibit the shift into
overdrive that could be defective. The manual shows one but there is no
provision for one on the block. Anyway, I have the control circuitry
bypassed and 12 volts applied directly to the solenoid, so it shouldn't
matter. What should I look for now? I have gone to several
dealers..service advisors and parts men looking for advice but everyone
comes up blank. Any ideas for further diagnostics?
miles. After driving for several hours on level roads at 50 to 60mph it
no longer wants to shift into overdrive. The hydraulic circuit of the
overdrive mode on the A43D transmission is electrically controlled. I
have bypassed the electrical control elements and have applied 12 volts
directly to the O/D control solenoid so I can manually control the
solenoid. It works fine when it has been driven for less than an hour.
But it still has the same problem of not shifting into overdrive when it
reaches its maximum operating temperature. There does not appear to be
a thermo-switch on the vehicle that would inhibit the shift into
overdrive that could be defective. The manual shows one but there is no
provision for one on the block. Anyway, I have the control circuitry
bypassed and 12 volts applied directly to the solenoid, so it shouldn't
matter. What should I look for now? I have gone to several
dealers..service advisors and parts men looking for advice but everyone
comes up blank. Any ideas for further diagnostics?
Bob Chufo in Pittsburgh
rk...@cdc.gov
Sent via Deja.com http://www.deja.com/
Before you buy.
jiva
Aug 1, 2000, 3:00:00 AM8/1/00
to
No thoughts on the problem but have u tried additional cooling as a solution?
olepat
Aug 1, 2000, 3:00:00 AM8/1/00
to
I had overdrive trouble on my '88 2wd 22re a while back and will
try here to remember how the system worked. Maybe the 12 volts to
the solenoid is there only so that 4th (overdrive) can be
disabled until warmup. In other words, after a temp sensor says
so, the
solenoid opens a port to 4th gear which stays open & allows 4th
to shift whenever demanded. Make sense? Now, what I did was to
run a test light from the solenoid wire into the cab to observe
the circuit. All was fine. When the truck engine reached temp,
the
solenoid wire was energized. My problem was the solenoid
itself.*** Broken wires at the top of the solenoid barely
contacting***. I
sort of eliminated the valve body as the problem 'cause the
overdrive worked some of the time. The gist of this, is that I
am suggesting
that the solenoid doesn't open and close constantly to shift
4th. It remains open when the truck is up to temperature so that
4th can
shift in and out whenever it is called for. Check for broken
wires at the solenoid. I noticed that the new solenoid was
reinforced in that
area. Mine was s snap to change. Totally external. Cost about
$140. If I'm wrong about all this, never mind.
try here to remember how the system worked. Maybe the 12 volts to
the solenoid is there only so that 4th (overdrive) can be
disabled until warmup. In other words, after a temp sensor says
so, the
solenoid opens a port to 4th gear which stays open & allows 4th
to shift whenever demanded. Make sense? Now, what I did was to
run a test light from the solenoid wire into the cab to observe
the circuit. All was fine. When the truck engine reached temp,
the
solenoid wire was energized. My problem was the solenoid
itself.*** Broken wires at the top of the solenoid barely
contacting***. I
sort of eliminated the valve body as the problem 'cause the
overdrive worked some of the time. The gist of this, is that I
am suggesting
that the solenoid doesn't open and close constantly to shift
4th. It remains open when the truck is up to temperature so that
4th can
shift in and out whenever it is called for. Check for broken
wires at the solenoid. I noticed that the new solenoid was
reinforced in that
area. Mine was s snap to change. Totally external. Cost about
$140. If I'm wrong about all this, never mind.
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Doyle Wilhoite
Nov 9, 2023, 6:49:08 PM11/9/23
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