Yes, 7747 applications expect 2k ppm. They were developed when the speedometer cable drove the speed sensor. I can cross check a 7427 wiring diagram against the DRAC outputs to determine speed signal frequency on F13. The "output speed not from DRAC" selection might be shown in the manual trans comparison thread currently running?
FYI DRAC on 1227747 and VSSB on 16197427 and they do not interchange.
1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
-= =-
I know on mine, it did not read on the datalog dash untill I selected "vss not from drac". Once I did it started working. I am using the JTR 2ppm vss.
79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy
93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver
99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.
X2.Originally Posted by JeepsAndGuns
(Extra letters because X2 is simply too short.)
Familiar with 1227747 and 16197427 PCMs
VSSB is a type of DRAC. Original reprogramming docs didn't even say "VSSB". All my data shows the "white box" versions are plug compatible but if you have something different I've got an open mind. Earlier trucks had DRAC built into the back of the dash and was programmed with a special fuses instead of resistors. Reprogramming meant popping all the fuses then installing a specal programming key which was nothing more than a series of jumpers. I've seen some vehicles where dash programming clip is set for "divide by" ratio of 1 and white box DRAC is installed.
Well they are both white boxs and they both have the same plug. But inside DRAC is one set of jumpers, inside VSSB is 2 sets of jumpers. If you plug a DRAC into a VSSB system it melts the new DIP switch. I haven't done much testing after that...
1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
-= =-
I think you had other issues, since I haven't heard of anyone else having that issue.
The man who says something is impossible, is usually interrupted by the man doing it.
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