I recently swapped a new modulator into my c4, a green stripe....but i also found that my shifting is much quicker, in other words i shift up in much shorter sequence and dont get to use full powerband, is there another type of modulator, like a white stripe that will allow me to employ higher revs? I use my rig 95% street
Types of vacuum modulators available for the C-4 and C-5:
Push-In or Bracket Mounted Modulators:
1) Red-stripe with two vacuum inputs. (large & small) Usually found on earlier (73-74) vehicles where EGR Devices were first introduced. This can in most cases be replaced with the green stripe version and get better results for the shift characteristics. The red-stripe dual diaphragm equipped C-4s use a different modulator retaining clip. This retaining clip is held in place by an extension housing bolt that is located just above the modulator. When changing the modulator to a single diaphragm type, you need to get the correct retainer from the dealer or the boneyard. C-5s also use the same C-4 retainer made for the single diaphragm modulator. The dual diaphragm retainer will cover access to the hose connection on the single diaphragm modulator. The retainers are made of spring steel.
2) Yellow stripe, with one single hose connection for High Vac lower altitude driving. Usually found on larger engines with strong vacuum signals, and trucks with earlier governor shift point calibration. Usually found on 72-81
3) Blue stripe, with one single hose connection for engines that generate slightly higher than average vacuum signals. These fit a small variety of applications of the C-4 & C-5. This version seems to be very uncommon but finds its performance levels between that of the yellow and green paint stripe codes. Usually found on 79-83
4) Green stripe, with one single hose connection for average settings that fit the widest variety of applications of the C-4 and C-5. This version seems to be the most popular and widely used of them all. Usually found on 72-83
5) White stripe, with one single hose connection for average settings that fit the widest variety of applications of the C-5. This version seems to be popular in C-5 with the V-6 engine but can also be used on the C-4 and seems to work well with them when operating at altitudes above 3000 ft. Usually found on 81-83
Thread Mounted Modulators:
1) They can have either a White or Green stripe, with one single hose connection. These are
the only modulators available for C-4s built before 1972 and work well on engines that have little or no emission control devices. Usually found on 64-71. This same modulator works on C-6’s that use Thread Mounted modulators.
I hope this helps you in choosing a suitable replacement for your vehicle. I also hope you have a better understanding of the differences. At this point, I think if you went with a white stripe, it may make it worse. The blue and yellow codes will produce later shift points and are more suitable when used with heavier governor weights on trucks, as opposed to passenger cars.
~BH~
