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Transmission problem ONLY when wet

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Old 04-12-2013, 05:37 PM   #1
CarlMac [OP] CarlMac is offline
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Transmission problem ONLY when wet

Hello, long time reader, first time post.
I was hoping someone might be able to offer advice on my problem.
I have a 1995 Tacoma, auto, 2.7L with 215K on the clock. I maintain it well and regularly change all fluids and other maintenance items when scheduled. I have this problem which has just started.
When driving in rain the trasmission doesn't work properly.
- It will stay in 3rd when I slow down, stop and then start again.
- It will intermittantly change down gears while driving on hwy.
- Feel real "Chunky" / "Clunky" like it is trying to shift into/out of another gear.
- Although, will shift no problem when I manually shift through the auto transmission
After I let it sit and dry out for a few hours it is fine. Drives beautifully like nothing is wrong.
I have checked what connections I can find and applied dialectric grease thinking that I am getting a short somewhere and no luck.
Please can someone offer advice, we have had plenty of rain and more comming!!
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Old 04-12-2013, 10:51 PM   #2
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Wow, weird problem.
All I can think of is a leak in the windshield area, that drips down to the ECM or tranny computer.
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Old 04-13-2013, 05:58 AM   #3
CarlMac [OP] CarlMac is offline
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Wow. Is right...
I just sealed up a leak in my windshield. It was a pretty good amount of water leaking in from the top directly above the rear view mirror.
Where is the ECM and tranny computer located?
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Old 04-13-2013, 10:35 AM   #4
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Quote:
Originally Posted by CarlMac View Post
Where is the ECM and tranny computer located?
I have a '99 with automatic, and the ECM is right behind the glove box,
which you have to remove, to get at the ECM.

Some vehicles have a separate computer for the tranny, and yours may not.
Mine does not, so its all in the central ECM.

One other possibility is the VSS (vehicle speed sensor) which is attached to the tranny body, and therefore very exposed to the elements. Crawl under there and check the connection. I would remove the electrical connector (careful, don't break it) smear some di-electric grease on the connection (enhances electrical connections, and maybe seals out water), and reconnect.

These are only wild-ass guesses, I hope someone with more tranny experience will chime in and offer additional possible solutions.

BTW - Removing Toyota electrical connections can be tricky if you are not used to it. There is a small tab(?) that you'll have to either pull out or depress to 'unlock' it, and pull at the same time. Annoying design, but it prevents the connection from accidentally becoming disconnected, and increases overall reliability. Some of these connectors have a little o-ring to prevent water from getting in.
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Old 04-14-2013, 01:12 PM   #5
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The 95-99 have a single ECM that controls the engine and transmission. It is located behind the glove box (as mentioned) and if it gets wet, can cause all sorts of issues. Since it seems to be fine until it rains, and you have already sealed the windshield, I would look at pulling the connectors at the ECU and checking for residual moisture and/or corrosion/rust on the terminals and connectors of the ECU. Beyond that look at the connector that goes into the transmission to see if the connector is not keeping out water like it should.
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