Dyna flow won't shift into low

55 century Trans won't start out in low gear when shifting from park or reverse. Also wont downshift while driving. Has to be manually shifted. Any thoughts? Thanks guys RS59

 

I may be incorrect here, but I seem to remember they don't start in "Lo" when "Drive" is selected. Dynaflows don't shift, unless, as you have discovered, you manually move the selector to Lo then Drive.

 

Dynaflows don't shift like most automatics. They just go as you speed up. The old ****** guys I have talked to do not recommend manually shifting dynaflows.

 

I have to agree with 41super, that is the way a Dynaflow rolls.

 

As mentioned, it sounds like your transmission may be working exactly as it was designed to. The intention was that you'd never feel any actual upshifting or downshifting under most normal driving conditions. (This is similar to what more recent Continuously Variable Transmissions are trying to accomplish.) This was done by filling and draining different areas in the torque converter under different conditions. It looked good on paper but there was a lot of lost efficiency in how it was accomplished. Just take a look at this mess.



According to this Dynaflow Wiki page...

"In 1953, Buick redesigned the Dynaflow, calling it the "Twin Turbine Dynaflow". The converter now incorporated two turbines and a planetary gear set, with a single stator."

http://en.wikipedia.org/wiki/Dynaflow

 

Thanks guys