VSS Eqiuipped Speedo Disassembly & Talk

89Suburban · Nov 25, 2012

Ok, heeeere, we go, 89S is bored and stuck inside the house with the kids, so let me take it out on something.

I decided to bring this guy home from PAP to do write up. Please feel free to share your thoughts and opinions and other info.

First off, is the VSS, mounted with one screw on the back of the unit to the right of the cable tower:

It senses that passage of the spinning bracket inside the housing:

89Suburban · Nov 25, 2012

Here are the components located behind the gauge pod. If anybody know how this works please chime in, lol.

Sensor, red, green, and black wires:

Those wires run into this device:

Coming out the other side of the device is one black single wire plug with a solid yellow wire that disappears into the truck harness. Also coming out is a white 3 wire plug with the following wires - pink w/black stripe, black w/white stripe and solid brown:

A shot of the socket with the plugs removed:

89Suburban · Nov 25, 2012

Opened up for view of the internals:

foamypirate · Nov 25, 2012

The yellow output wire is for the cruise control. Non-ECM trucks (like my 84' I6) with cruise only had that single wire. ECM equipped trucks (not sure if this includes CCC trucks) use the other output for the computer.

89Suburban · Nov 25, 2012

Now onto the gauge. First removal of the needle. Keep in mind to reinstall and line up the way you want will be very difficult. You may want to pick a spot on the gauge, say the 5 MPH mark, aim the pointer at it, then mark the drive cup to the housing in back of the number counter assembly.

Like Retro pointed out, a great tool to remove these with minimal damage is a fork.

89Suburban · Nov 25, 2012

foamypirate said:
The yellow output wire is for the cruise control. Non-ECM trucks (like my 84' I6) with cruise only had that single wire. ECM equipped trucks (not sure if this includes CCC trucks) use the other output for the computer.

So can you use this just with the one yellow wire to run a cruise control setup? Or do the other wires need powered or whatnot to make it work? Might be a good mod for non-VSS carbed truck owners out there, if they can slap this on their speedo and add cruise?

89Suburban · Nov 25, 2012

Next remove the face by removing the 2 slotted head screws:

(Note the trip odometer adjusting stalk was already broken off the inner housing)

89Suburban · Nov 25, 2012

Next a 3/16 socket is used to remove the screw holding the drive cable retaining clip and rear gasket. This may actually be a metric size but I got 3/16 to work:

89Suburban · Nov 25, 2012

Next is two more 3/16 or metric equivalent screws holding the front and rear sections together:

The left side is VERY tight, you will need a tapered, deep, 1/4" drive socket, this one barely made it: :wtf:

89Suburban · Nov 25, 2012

These are the 2 drive gears that run the mileage counter. Removal of either one or both will disable the mileage counter and trip OD, but will not affect operation of VSS or MPH reading. :emotions33:

89Suburban · Nov 25, 2012

Here is a close up of the rear case gears:

Here is what is left of the rear case. The driven piece the cable spins that has a light magnet built into it. When positioned inside the drive cup on the front housing the magnetic field creates a resistance, speed dependent which in turn rotates the drive cup to a predetermined position, in turn pointing the needle on the gauge to the appropriate speed on the dial face. I don't see a way to take this section apart any further. Not sure if the parts are pressed together. I will report back on that. :evillol:

89Suburban · Nov 25, 2012

Ok, I figured it out. The drive shaft at the rear is hollow and the tip of it is crowned over to hold the brass collar. Just a matter of pressure to straighten the crown and slide the brass collar and washer off. I was a little rough on it but I believe this can be done with some finesse, patience and smarts.

Then the shaft pulls out the front of the housing. The shaft is stepped in 2 spots where lube can be held, so if you go to pull this apart to re-lube, it will not be in vain, as long as nothing is damaged in the process. I assume a flaring tool or similar type of device can be used to re-flare when re-assembling.