Will not shift past first gear

1985 FORD BRONCO
300,000 MILES • 6 CYL • 4WD • AUTOMATIC
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JOHN R. FORD
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  • 1 POST
Truck sat for about a year. Finally fixed the brake system, so i started to drive it again. started out fine, but gradually it started to struggle more and more to shift up. has now stopped shifting up entirely. i get to about 25 mph, and the engine will just keep revving, with no more power output. i am reluctant to push it any harder for fear of causing damage.
Sep 20, 2019 at 7:42 AM
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MASTERWRENCH
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  • 258 POSTS
Welcome to 2CarPros.

The shifting in your transmission is basically controlled by two components. The governor(controls shifts based on vehicle speed) and the vacuum modulator(controls shits based on engine load/acceleration). Let's try to narrow it down a little before getting too deep. Have you tried manually shifting the transmission? For example, place the shift lever in 1 or L while at a stop. Begin driving and move the lever up to the 2 position as appropriate and then up to D. Does it up-shift while driving in this manner?

Thanks.
Sep 21, 2019 at 6:53 AM