I just got my C-4 back from overhaul & in the car. It is not shifting right @ low RPM. I just had a stock kit put in it and seals + torqe conv. I have checked the fluid levels and they are good. Some have told me you can adj. the Modulator for slower or quicker shift. Does anyone know which way to turn the screw on the mod. to make it shift sooner with less vac. Or do I need to improve the amount of vac. But it shifts fine out on the highway with more RPM's. Thanks for the Help!!!
Up Date: I called the guy that did my tranny. He said check vac. should be 15#'s @ idle, clean lines & retry. Next if that doesn't work adj. mod counter clockwise for earlier shift. He thought the mod should have been pre set in kit but, was very understanding of my stupidity!
The adjustment on the modulator is a screw. turn it in to increase the speed of the shift (later shifts) turn it out to reduce the speed of the shift (earlier shifts) never turn it more that 4 turns in either directions from center. It should shift into second under light throttle at about 12 mph.
i think it was his...stupidity!...to think that they are always right ...new, out of the box . ... ...
Well the tale continues: Vac is good #20 @ idle, fluid is good HOT. Talked to a local mech. today (borrowed his vac gauge) he said check kick down linkage sounds like sticky valve body. My kickdown is not connected but I checked to be sure it was not stuck down (& it wasn't). It's raining today so I didn't take it out but did last night. She (notice if she were working right "she" would be a "He" or a "Honey") shifted from low to second @ 15 mph & shifted to drive @ 50 to 55 mph. Now the local guy said " if you adj. the modulator that will also make it shift sooner from low to second which now seems to be good to me. So I'm still lost, he thinks sticky valve body ??? I asked if he thought flushing it would help he just looked at me. Any Ideas or take it for a long drive and see if it comes out of it. Thanks Guys!!
If your transmission is shifting from low to second at 15 MPH with full throttle then you have a problem. If your downshift linkage is not connected then get it connected. If it shifts from low to second at 15MPH as you normally pull away from a stop then you don'y have a problem - it is supposed to shift between 8 and 15 MPH at light throttle from low to second. It will shift from second to third at 20-25 MPH under the same conditions. If you are holding your foot to the floor it should shift at about 4200 rpm. It will not shift that late with the downshift linkage disconnected. The downshift valve increases throttle pressure to overcome modulator pressure and make the car stay in a lower gear when the vacuum is high enough to shift the tranny into the next gear. Connect your kick-down linkage and my bet is that your "problem" will go away.
Quoted for TRUTH, brutha! Seriously, there's like, nof***ing way they're "always right new from the box"
i have heard that you should not adjust it too much or it could cause problems in the tranny since i put the 4.11 gears in mine.. it shifts immediately into 2nd. i have to manually shift mine now
Well the best I can get here is : I need to break it in or I have a problem with the valve body. Put on a good modulator, have 25lbs of vac. @ tranny and it shifts perfect into second from stop sign takeoff. Shifts perfect on the highway all three gears up & down. But will not shift around town into third (drive) manual or otherwise without getting to about 45 miles per. I am going to take it on a highway drive and see if that helps. Weather hasn't been the best when I am off work. Thanks Guys!!!
isn't there like a little needle valve or something behind were the modulator is???? I had a shifting problem years ago and I seem to remember that "needle" had been left out after the rebuild. I am probably way off on this one, just thinking out loud.
There is a pin between the modulator and the valve. If it is left out the transmission will shift extremely late and hard. If you screw the adjustment in too far the same thing will happen. It sounds like the modulator adjustment has been screwed too far and now part throttle shifts are not happening at the rpm that they should.
The needle is in guys. I checked my self when I changed to the new mod. This weekend is the BIG test, the weather is going to be 80's and sunny (NO RAIN). I'll see if this does it or its back to the board, I'll keep you posted! Thanks Again!
