speed sensor question

[skandolis]

thanks guys, i guess i should have been more clear about what im asking, i do have the little yellow speed buffer on the back of the speedometer. What signal (ppm) comes out of this? i have a drac from the truck that supplied the pcm. i guess basically i would like to run it into the drac in order to use jumpers to "correct" the signal going into the pcm, so at least the pcm would see the right speed. (speedo is off by about 40 percent or so(reads 35 or so close to 60 mph) due to my inability to locate the proper drive gears in the tailshaft for the 2.56 gears in the rearend.)

i do have the parts to convert the trans to electric speedo, but i spent a lot of time getting the third gen camaro dash to fit, would like to keep it if possible.

[S.O.B.B.]

What transmission do u have and do u have cruise control. These pics are off jagsthatrun. Number 3 in the one pic and the one on the right in the other pic is what I think u are needing.the signal from that goes to the speed buffer for the 427.the buffer also feeds the cruise control and has outputs to use electric speedo.vehicle-speed-sensors.jpg4-pulse-integral-VSS.jpgpinout_e7e48f8aece2b857adf1b18fa4099bf7f53fa940.jpg

[S.O.B.B.]

That will get u a signal to ecm but it will still be off till u get the correct gear.there is info out there and probably on here about changing the jumpers inside the buffer to get the desired values.

[stew86MCSS396]

thanks guys, i guess i should have been more clear about what im asking, i do have the little yellow speed buffer on the back of the speedometer. What signal (ppm) comes out of this? i have a drac from the truck that supplied the pcm. i guess basically i would like to run it into the drac in order to use jumpers to "correct" the signal going into the pcm, so at least the pcm would see the right speed. (speedo is off by about 40 percent or so(reads 35 or so close to 60 mph) due to my inability to locate the proper drive gears in the tailshaft for the 2.56 gears in the rearend.)

i do have the parts to convert the trans to electric speedo, but i spent a lot of time getting the third gen camaro dash to fit, would like to keep it if possible.

I think it depends on what year thirdgen...IIRC the '85-'89 put out 2000k whereas the '90-'92 went to 4000k. I'm sure what you're trying to accomplish will work as long as you can get the signal from the DRAC to the PCM. From there, you can use your datalogging software to display your actual speed. I'm sure you're familiar with the DRAC jumper mods.

[dave w]

thanks guys, i guess i should have been more clear about what im asking, i do have the little yellow speed buffer on the back of the speedometer. What signal (ppm) comes out of this? i have a drac from the truck that supplied the pcm. i guess basically i would like to run it into the drac in order to use jumpers to "correct" the signal going into the pcm, so at least the pcm would see the right speed. (speedo is off by about 40 percent or so(reads 35 or so close to 60 mph) due to my inability to locate the proper drive gears in the tailshaft for the 2.56 gears in the rearend.)

i do have the parts to convert the trans to electric speedo, but i spent a lot of time getting the third gen camaro dash to fit, would like to keep it if possible.

A 2K Pulses Per Mile (PPM) VSS signal can be sent directly to the 16197427. Typically 1993 - 1995 vehicles with a 16197427 using either a 4L60E / 4L80E transmission Do Not have a speedometer cable. Typically the DRAC converts the 40 Pulses Per Driveshaft Revolution (40 PPDR) signal coming from either a 4L60E / 4L80E into a 2K PPM for the 16197427. The DRAC is used to supply other outputs for the , Electronic Speedometer, PCM, and Rear Wheel Antil-Lock (RWAL) brakes. Here is a link to Calibrate a DRAC http://tbichips.com/?page_id=504

Perhaps this link will help with understanding the options available to successfully use the Third Gen Camaro speedometer: http://www.jagsthatrun.com/V8-chapte...ed-Sensors.pdf

dave w

[stew86MCSS396]

dave w thanx for explaining that...I recant what said above...totally misunderstood where the DRAC gets it's input from. I'm still curious as to what transmission is being used as it appears you can get about any gear from flea bay. Or perhaps the real issue is...gotta drop the trans, pull tail shaft off, change drive gear, etc, etc...easier to fool something with a keystroke!!!

[S.O.B.B.]

Dave w thanks for clearing that up.I read so many different things trying to figure how I'd make my set up work.I had opposite were I could no longer run the speedo cable due to trans having a pulse ring and sensor.I didn't know the 427 would and accept 2k pulse.that's interesting because in my plan to go back to auto trans I thought about converting the cable drive on the auto to electronic so I didn't have to mess with the speedo issue again.but at least now I know I could go back to cable if I had to and get the signal to the ecm.good info.thanks

[skandolis]

thanks guys! think im on the right track now. trans is a 700r4, i have actually bought gears twice now, the aftermarket color/number of teeth don't seem to match gm stuff, may try again later to get the speedo working.

[FieroDoug]

If I am hearing correctly: in my situation, installing a muncie m-21 behind an '86 TPI with factory wiring and computer, I can find and use the OE 86 yellow box, and cable from tranny to yellow box, plug the harness from yellow box into computer, and cable out of yellow box to my aftermarket mechanical gauge, and I should be okay. Obviously, I need (and have) the correct cable drive gear that matches the rear end gear ratio.
Is that correct?
Obviously, I will need to reprogram the computer for the manual tranny, and I have the code for that ('89).
I tried ordering the JTR generator, but they were out of stock and refunded my $$ after I waited several months.

[FieroDoug]

Upon additional research and seeing the yellow box...the answer is, "if installing the OE Camaro speedo, yes use the yellow box. The speedo is mechanical, but has atached the pulse generator, which the yellow VSS buffer then plugs into. if installing aftermarket mechanical speedo, source the 2PRS unit from JTR. If installing an aftermarket electronic speedo, probably ok to use the OE tranny mounted VSS."