Technical 1962 390 with C6 not shifting right

I usually do not mess with Ford engines and transmissions, mostelly Chevy stuff. I have a 62 thunderbird that I went through the engine over the winter and replaced all the gaskets, added an aluminum Edelbrock intake and also a 600 edelbrock Carb. My issue is the transmission is not shifting until very high RPM's unless I either get on the gas or let off of it for a bit. The Vaccum line from the trans and the booster are hooked to the original vaccum tree put on the new intake. The trans also takes a little longer to downshift when stopping. Any help do diagnose the problem would be appreciated.

 

did you change it to a c6? should be a cruise o matic.

 

Did you replace the vacuum modulator? Could be bad.

 

What kind of fluid do you have in it? If I remember correctly C6's (if, as glendale said, it's really a C6) take Type F fluid which can be hard to find. Not sure if that would have that much of an impact but could be a possibility.

 

The car does have a C6 in it. It does have Type F fluid in it, found it at O'Rileys. I have note replaced the vaccuum modulator

 

If you have indeed converted to a C6 (or if someone did so before you) it must be determined if the kick down linkage is set up and adjusted correctly. If the linkage is moving too far too soon your shifting will react as though you are deep in the throttle. The modulator valve of a C6 will require manifold vacuum. If the vacuum source is weak it will react similarly to a maladjusted kick down linkage. Check for vacuum leaks. If you have a second source for manifold vacuum, try that.

 

With the vaccum to the trans currently hooked to the vaccuum port tree, What port on an Edelbrock 1406 would be the best to connect it to?

 

The PCV port on the Edelbrock AFB gets manifold vacuum so that is one to try. Also the 3/16 manifold vacuum port will work. The tree is plumbed into one of the runners typically and is also manifold vacuum but why not move it and see what happens. At least that is some sort of data point. (The 3/16 timed vacuum port on the carb is for distributor vacuum advance if not using manifold vacuum for that purpose.)

How is your kick down linkage? You might try disconnecting it and driving easily around the block to see if the shifting is any different.

If the rod used with the modulator is the wrong length it will have an effect. Also, the modulator is adjustable by using a hex key or slotted screwdriver through the vacuum tube to effect earlier or later shifting but best to search on that and leave it for later testing. Usually if the daiphragm in the modulator is defective it will allow ATF to get sucked into the engine resulting in a white cloud from your exhaust but I suppose it might fail without leakage and then your shifting would be late. In high school I had a C6 with a loose vacuum hose that would fall off once in a while and when it did that car would not shift into third. So too little movement or too little vacuum will have this late-shifting effect.

 

Thanks for the input guys. I worked on it for a little while last nite and adjusted the kickdown some and it is shifting too quick now. I will work on it a little and adjust the kickdown some more and hopefully that will resolve my issue. All of your inputs are appreciated.