Transmission not shifting properly

1993 FORD F-350
156,000 MILES • 5.7L • V8 • 2WD • AUTOMATIC
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GAILMAC2000
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My transmission will shift hard into second, but will not shift at all into third. I can manually shift from second to third and it works just fine. The light does not work on my overdrive button, so not sure how to know if in overdrive or not.

Any ideas what is wrong?

The transmission was replaced about eight years ago, but only has about 10,000 miles on it.
Thanks for any help.
Aug 9, 2018 at 6:30 AM
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STRAILER
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This sounds like a partially plugged catalytic converter which will change the engine vacuum readings causing the transmission to shift late. Here is a guide to help you confirm the issue:

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

Please run down this guide and report back.

Cheers, Ken

Aug 10, 2018 at 12:47 PM