I recently installed a B&M shift kit in my C4 transmission and ever since it shifts from 1-2 and 2-3 way late. I have to let off the gas and make it shift so I do not over rev the engine. I put the shift kit in to get firmer shifts but did not want it to stay in gear longer, especially this long. I did not have this problem until after I installed the shift kit. I reread the directions, which are poorly wrote, and it does not say what mod causes it to shift late. I just want to change it back to stock if I can. Can someone please give me some advice!!????
I wish I could find a good tutorial on how the C4 governor, modulator and throttle pressure rod interact to determine up shifts, down shifts, and shift firmness under light and heavy throtttle. I'd like to tweak mine but don't know what the effects of most tweaks would be.
Nick, it sounds like the modulator valve needs adjusting, or you might have left a vacuum line off. Take a look to see if the modulator is adjustable, and check the hoses......other than that...??????
Nick, I have the opposite problem. My c4 is shifting 1-2 at 10mph and is in 2-3 before 15. Stopped at the tranny shop yesterday and they said to screw the modulator screw in about 4 turns to give it less vacuum. If you don't find any lines loose try turning it out and see if that helps. Just remember how many turns you go. Actually I don't think just a new shifter should change the shift points if you leave in drive. Hope you find the problem.
How do you adjust the modulator valve? If I shift the transmission manually it shifts fine if that means anything. I did put a half inch spacer on the carb which changed the angle of the kick down linkage a little but it seems like it moves freely and did not effect the travel length.
Basically it says jack the front of the car, use jackstands. Modulator is at the right rear of the tranny pan. Remve hose to modulator. Use flat screw drive. needs to be a small one. Turn clockwise for harder, later shifts and counterclockwise for softer, earlier shifts. Go one turn at a time. It says not more than 4 turns either way.
Nick, Make sure that you do not have a vacume leak in the line that goes to the modulator valve. On my 6 cyl car The trans shifted just fine , and then It started holding second gear way too long ... sometimes I would lift on the gas a little and it would go ahead and fall into third. I checked it out and the "elbow" shaped vacume line that connects the hard line to the modulator valve under the car was cracked and slightly collapsed (probably the original one.) I replaced it and the transmission has shifted out perfectly since then.
Mike, thanks, I will check it out. I replaced all the vacuum hoses, maybe it fell off. I hope it is that simple.
Nick, insure that the vac. line is the correct ID. could be a size too large and leaking around the connection... I find smaller ID on vac. lines are better than larger...being there is no clamp on a vac. line...
