hard downshifts on rebuilt c6

[1971ford]

today we were driving the 71 for the first time with the rebuild tranny and the 429. in the old truck that the combo was in, my dad thought the tranny was slipping. then we rebuilt it, and swapped in the converter out of the 360 since we knew it wasnt slipping.

the truck does not have a downshift rod*

when you give it gas, and it does the downshift, its pretty hard. you hear "clunk" and the truck kinda jolts. its downshifting hard. i think i made it sound alittle worse than it really is but my dad thinks its not right and the tranny is slipping, i think he is used to the 71 when it had the downshift rod that goes to the carb.

and when the engine/tranny was in the old truck, it didnt make such a hard downshift.
the only other thing we did to the tranny was a TCI manual/auto valve body.

other than that the engine/tranny felt great

[Jake11]

Take the hose off the modulator. Using a teeny flat blade screwdriver, turn counterclokwise " 1 " turn.
Road test. Report. Jake

[1971ford]

Take the hose off the modulator. Using a teeny flat blade screwdriver, turn counterclokwise " 1 " turn.
Road test. Report. Jake

what the heck does that do
im guessing there is alot more vacuum causing it to downshift harder, and the screwdriver turn will lessen the vacuum?

[Jake11]

It changes the line pressure. The modulator thing is a load sensing valve, that can jack the pressure up that
makes the hydraulic stuff in the trans work. Press. too high= it slams. Press. too low=it can slip. Try it.

Could also be valve body/govenor too. Try messin with the modulator first. It's easy to get to. Make sure it's got
vacumn from the motor too! Jake

[1971ford]

we drove the 71 for a while today. we still havent messed with the modulator though. but its not just the weird downshifting, but my dad says it shifts into 2nd too gently or something. and when you shift into 3rd it slips and does a hard shift. my dad says it would be a good shift into 3rd if it didnt slip right before.
my dad is wondering if adjusting the bands would have anything to do with it? that and the modulator?

[1971ford]

the tranny is still slipping a little before going into another gear

question time
-there is 20 pounds of vacuum going to the modulator. is this too much?
-how much can we turn the modulator thing to try and help the shifts?

when we got the TCI manual/auto valve body and installed it, it had this rod in the valve body. it has no grooves. the old one had grooves.so we put the old rod in the new valve body. (so the grooved one is in the valve body right now).
here is a pic of the TCI one that is in a baggie in my room for safe keepings.

-could that have anything to do with the problem?
-once we install the artcarr shifter and we replace the old rod (grooved) with the one the valve body came with(non grooved), will that fix it? because the grooves are what keeps you in gear, but the artcarr gate shifter would do that so wouldnt that fix it. well thats what im thinking.

thanks, this shifting is really annoying me

[fordman]

i'd follow jakes instructions. i have no idea abotu aftermarket parts into a transmission. but i would have used the rod that came with that valve body and not the ford rod. the aftermarket people put that one in for a reason. i'm not sure what marks would have to do with it unless i saw it in person. im not much on valve bodies anyway. my motto is never take them apart. just clean them and put them back in.