Transmission Trouble?
Thread Starter
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Senior User
Joined: Apr 2003
Posts: 415
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From: Jerseyville,IL
Transmission Trouble?
Got a '90 7.3L auto. When driving it at a constant speed, even with cruise on, the rpms fluctuate about 300 rpms bouncing between 1900 and 2200. What would cause this?
Post Fiend
Joined: Nov 2004
Posts: 5,638
Likes: 1
From: Manitoba
Your post states trans trouble, the tach fluctuating could be a bare wire at the sender or a loose connector. If you remove the sender and check it with an ohm meter while holding in air away from ferrous metal, you should get 2000-3000ohms resistance from the pins. If the face is dirty and you clean it sometimes this will help for a few weeks. Ford only part.
If the tach is sending bad info the trans may react to it.
If the tach is sending bad info the trans may react to it.
Thread Starter
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Senior User
Joined: Apr 2003
Posts: 415
Likes: 0
From: Jerseyville,IL
I'm not sure if it's the tach causing it though. The engine changes with the tach (I shoulda stated that, sorry), and at certain speeds it doesn't fluctuate at all. It's real bad at about 37 mph and again at about 60mph. I can drive 35 and under it won't fluctuate and from about 45-55 it won't do it. It acts like it's not sure which gear it should be in at these speeds. It was worse, but we replaced the pressure soelenoid thing inside the tranny and it helped but didn't solve it completely.
Post Fiend
Joined: Nov 2004
Posts: 5,638
Likes: 1
From: Manitoba
You don't rest your foot on the brake do you, the TC will unlock with any brake light inputs and this would result in a 200-300rpm increase. Do you get the rise in Cruise control and with Cruise off correct. Did you change the trans filter recently around the time this started. Is your MLP sensor set correctly, don't have to play with shifter to start the truck. Did you check for codes...
