When transmission is shifted into drive the transmission it stops the transmission from shifting

1994 MAZDA B4000
280,000 MILES • 4.0L • V6 • 2WD • AUTOMATIC
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VINCENTROSE96
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  • 2 POSTS
When I put my transmission in drive It doesn't shift at all anymore. So I have been using the overdrive but now I have to red line it to get it to shift out, and then when it reaches its last gear the whole truck shakes. The transmission seals were replaced about 2 to 3 years ago it's also full of transmission fluid and doesn't have any visual leaks. Not sure if this matters but its a salvage rebuilt vehicle and I have replaced minor things over the last year such as maf sensor, tbp sensor, PCV valve, and it now has a cold air intake as well. Any help with this transmission problem would be great.
Jul 4, 2021 at 5:07 PM
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JACOBANDNICKOLAS
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  • 110,175 POSTS
Hi,

That is a tough one. It sounds like a pressure issue in the transmission. Do me a favor. Let's see if there are any diagnostic codes stored. This has an OBD1 system. All you need is a short jumper wire or even a paper clip.

Follow this link and let me know the results:

https://www.2carpros.com/articles/diagnostic-trouble-codes-for-1995-and-earlier-mazda-cars-obd1

Take care,

Joe
Jul 4, 2021 at 9:11 PM
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VINCENTROSE96
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So I have multiple codes but not sure what any of them mean. But they are 33, 11, 76, 18, 61, 89, and 21.
Jul 6, 2021 at 2:29 PM
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JACOBANDNICKOLAS
  • CERTIFIED EXPERT
  • 110,175 POSTS
Hi,

I read through all the codes. All are related to the engine except 1 and that is code 89. It is a converter clutch override circuit failure. The override is just that. You have the option of tow mode which prevents it from engaging. However, I find it hard to believe that would prevent the transmission from working.

Here is what I need you to check next. There is a vacuum diaphragm on the side of the transmission. Make sure the vacuum hose is connected. Also, remove the hose and check for vacuum when the engine is running. Also, check to make sure there is no evidence of transmission fluid in the vacuum hose.

See pic 1 below.

Let me know what you find.

Take care,

Joe

See pic below.
Image (Click to enlarge)
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Jul 6, 2021 at 9:55 PM