Imperial Home Page -> Repair -> Transmission -> Torqueflite -> Kickdown
Question from Peter (1957):
But I've a little thing that bothers me: the transmission doesn't kickdown! If I smash the gas pedal to the floor, the car remains in the same gear (3rd if it was in 3rd, 2nd if it was in 2nd). On the other hand if I slow down the car (with brake applied or gas pedal released) the transmission downshifts to 2 or 1. I've checked the kickdown linkage adjustment, according to the FSM and all is OK. The transmission has been overhauled. I noticed also a small slippage when the transmission upshifts from 2 to 3 but not every time. And sometimes also the transmission doesn't want to remain in 2nd, it upshifts quickly in 3rd .. except if I push the "2" button. Any ideas what is going on?
Sounds to me like something in the valve body is not right. Maybe a pressure adjustment or maybe not all the little steel balls were inserted back correctly in their respective places or maybe one of the spring loaded valves was assembled incorrectly. I had a similar kickdown problem with an old AW 35 on a 79 Volvo which was caused by a technician using the wrong gasket when putting the trans back. But the problem was kickdown only, not the upshifts thing you refer to.
On Chevy cars ( early) you hold the gas rod open (engine off) and adjust the kickdown rod so that it just fits the hole in the linkage of the carburetor. If the kickdown rod is shortened the trans will shift sooner or later if you elongate it. You may have it at the point where as it try to shift, the linkage is at that point where the down shift is located.
I have never set the linkage on the cast iron transmissions but I would think they are similar to the aluminum cased ones. sometimes they can be a bear to get just right and they have to be just right or they won't shift. Been there many times. Follow your FSM to a T and keep doing it until it is right. Any slack in the linkage will cause a maladjustment as well as the choke not being fully closed. I always block the choke wide open and use a spring to keep the linkage tight against the boss on the tranny itself. Or if you have 2 people, one underneath to hold it tight while the second adjusts the linkage above. There should be a hole in the mount where the throttle cable goes and you need to put a rod that fits tight through that hole and the linkage to keep it lined up. I use an 1/8 inch drill bit. Make sure the springs are reconnected properly as well and they are the right ones! I had one car that had them backwards and kept too little of tension on the kickdown linkage.
Another reason why you can have an erratic kick down is due to the two rubber bushes that are directly located within the kick down linkage system. The first one, as you are aware, is in the transmission case where the small shaft comes through approximately 20mm that has then the lever which fits on top (hope I'm describing this alright). The other rubber bush sits in the end of the lever where the kick down linkage locates into. I had to replace both rubber bushes. When they start to wear they can give a false indication that the kick down is adjusted due to the excessive play within the linkage system. My advice for the bush located on the end of the kickdown lever is to have a little urethane one machined and fitted. The one in the transmission case also acts as an oil seal.
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