Vehicle Speed Sensor BUFFER needed

Under the dash, attached on the left side of the flasher relay box, by the drivers left foot, is the vehicle speed sensor BUFFER.
It is a small box about 2x4x3/4 inches. It splits the signal coming from the 4L60 to the sppedometer and ECM.

I am NOT referring to the gear driven Speed Sensor Sender that is attached to the tail shaft of the transmission. This is the buffer under the dash.


I drive a 1993, so it's likley to be the same part on a 91-93.
I can't say whether the part from the 94-96 LT1 an 4L60E would be the same unit ot not.

it has two connection clips on it, One from the Tranny speed sensor has two wires. The other appears to have about 4.

How much with shipping to 14621? Let me know.

Dave Buchholz
Rochester, NY

Dave:

All the GMs from 84 to 93 with electronic dashes (my 89 GMC truck with analogue gauges for instance) had the same buffer. However, they do have different part numbers depending on tire size and axle ratios. There are a number of guys on Ebay that can reprogram this part for your application for under 100 bucks, including the part. However if you take your old one in to any junk yard, you could probably find one with the same number. When they upgraded the ECMs to OBD 2, they incorporated the buffer into either the body control module or the ECM.

Hope this helps.

Bill

The part is the same for all TBI B-bodies. The input determines the output. You can change the input with different VSS gears. I may be able to get one. I do not have a price at this time. Shipping is about $5-7. You can also use a square wave modifier to change the input. If you disconnect just the computer from it, the output for the dash will change to a higher pulse per mile by about 10%. I believe there is a load sensor in the unit, but have not analyzed the operation. It is supposed to have two outputs, the speedometer/odometer, and cruise control are at 4000 pulses per mile, and the computer gets 2000 pulses per mile.

Both my digital dash and ECM are reprogrammable easily by me, so I just physically need a working buffer. I'm not much for junk yarding. So if someone has one handy that has already been pulled, then I'm good to go.

 I'm running a Corvette tip 7730 ecm with an aftermarket daughter board attached that gives me programmability apart from a normal tbi system. Certain ecm functions need mph as a qualifier. My wallet and future speeding require that the Speedo works.

I will check in the next few days.

Fred, I was able to head over to the "local" junkyard, 30 miles away, and found a buffer in the only 91-93 B-body that was there. I now have a buffer in hand.

With my luck, even though the sender and buffer are replaced, it will be a different issue causing the problem.

Since you are not using the computer output from the buffer, do not be surprised if the speedo is off on the high side by about 10-15%.

I am using the output from the buffer. My ecm is programmable. It's a Covette ecm with a daughter board on it, called an EBL.The additional board can store eight programs, all readily reprogrammable from a laptop.

If you do not need an input for the ECM, you can leave it open, and it will increase the output frequency for the speedo/odo, and cruise control. You can change the VSS ratio to lower it, but I do not know the gear selection. The speedo/odo, and the cruise control are the same output, they just have different pins on the unit.

When I switched over to the Holley MPFI, and I no longer needed a speed input for the ECU, my speedo was way off. I used a pulse modifier to adjust the input from the VSS. With a 4L65 (not E) you do not need the output to the ECU for trans control.

Actually, on my system, you do Fred. It is needed to tell the ecm that the vehicle is not idleing, and above a certain speed to activate the TCC. Rpm and load is not the only factor this system uses.