Fluid Drive repairs

[Billyzack]

I have a 48 Desoto and it runs great but will not upshift from the low gears or from the high gears. It takes off well but when I let up on the gas, there is nothing. I have to rev high and it goes into the previous gear. I have checked everything I know how to do and think maybe I should have it looked at by someone who knows what they are doing. Does anyone know of a place in or around Phoenix. Or, what should I look for in the yellow pages? Thanks, Bill

[PatS....]

Are you sure you have the semi-automatic M5? Fluid Drive only refers to the Fluid Coupling replacing the flywheel. There COULD be a regular 3 speed transmission behind the Fluid Coupling. You would have to shift that transmission manually.

If your gearshift lever has a gear position toward you and down where first gear would normally be, then you have a regular 3 speed transmission. Drive it like any 3 on the tree.

If there is not a gear position where first would normally be, then you have an M5...which DeSoto called the "Tip-Toe" shift. The same transmission with minor wiring changes is used in 49 on but called the M6.

The first thing to check, if it IS the M5, are the wire connections on the transmission, carb and coil.

Second is the idle on the M5. If it's over 450 rpm. the trans won't shift up. It needs to drop that much for the shift to work.

Check those things and let us know if it will shift. There's more if it won't.

Nothing mysterious, it's a very simple system, really.

And LOTS of great help here on the forum.