How To Do The Electronic Speedometer

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How To Do The Electronic Speedometer

• In the event your Astro/Safari didnt have
  itLets go Electronic!
• Advance the show by mouse click or hit your
  spacebar.

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By 86astro

• This is the way of adding the 92-94 Suburban
  gauge cluster into your old fashioned cable
  driven Astro/Safari.
• I will show the proper way to hook up the
  electronics, as well as where to obtain the
  parts.

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Go from thisUGH!
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To This BIG Improvement!
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Lets Begin!!!

• The new cluster has a tachometer, which I wanted
  for the looks, and besides, I hate the graph
  paper look of the astro cluster.
• Some of big differences are
• Size of the clusters The Astro/Safari cluster
  is a little bit smaller in every direction than
  the new tach cluster. Many people have chosen
  different ways to mount the cluster, such as
  removing the lexan, boring out the dash, or even
  mounting it to the bezel itself. Different
  strokes for different folks

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• Oil Pressure Gauge - You need to pay attention
  to this because some of these clusters had
  0-40-80 psi, and others had 0-30-60. There are 2
  different senders for these, so make sure that
  you get the appropriate sensor for the cluster.
  The Astro I have uses the 0-40-80, and the
  cluster I obtained uses the 0-30-60. I will be
  changing sending unitslol
• Cable VS Electric - In my case, I had one other
  big hurdle to overcome. I had the issue of the
  cable driven speedometer, and this new tach
  cluster is electronic. This is not as big a
  problem as it would seem. I like crawling under
  greasy cars piled 2 high at my local yard. I have
  found 2 different schools of thought on how to do
  this job, I simply had to choose which school I
  wished to go to Lets look at each one.

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School 1 The Magnetic VSS

• Some folks get the magnetic type of VSS from the
  donor truck, and also get the little white DRAC
  box that goes with it. Then you can proceed to
  mount the VSS sensor and wire it to the DRAC. You
  MUST also remove your cable driven ring gear from
  the tailshaft, and replace it with the 40 tooth
  reluctor ring from the donor truck, or any other
  RWD GM truck, van, or car with electronic
  speedometer. If you do not use the 40 tooth
  reluctor ring, you will NOT get a signal.
  REMEMBER! If your Astro/Safari is a 89 or newer,
  this is what you should have, unless you have all
  wheel drive, then it looks a little different. I
  was going to use this, but I changed my mind

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The Ring

• This is the 40 tooth reluctor ring. I opted NOT
  to use this because I understand these are VERY
  brittle, and a real PAIN to install on the tail
  shaft without destroying the internal bearings in
  the transmission. The are made of pot metal and
  could possibly break too.

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Magnetic Sensor

• This is the magnetic VSS sensor that you would
  use if you were going this route. It installs the
  same way the cable driven gear did.

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The DRAC

• This picture shows the DRAC unit that is needed
  for the swap as well. Bear in mind, that you
  should look for a truck that has the same gear
  ratio that you have and remove the unit from that
  vehicle, otherwise there is some complicated
  jumpers that need to be installed and reset. If
  you get the correct one, it just makes the whole
  job easier. I found my DRAC in a truck equipped
  with 3.73 rear gearsJust what the doctor
  ordered!
• The DRAC usually resides behind the glovebox
  area, and is generally velcrod to the top of the
  glove box itself. Simply remove the glovebox and
  you should be able to peel it off. Remember to
  get as much wire as possible, you will be glad
  you did.

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DRAC Wiring

• This is one of the wiring diagrams used for the
  DRACUse caution, and look into the shop manual
  for the exact diagram, they may be different
  according to truck and options.
• Class Dismissed from School 1.

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School 2 The Gear Driven VSS

• Another way to add the speed sensor to your
  system is to use a VSS speed buffer module that
  was used on the 1986 to 1992 4 cyl. and 6 cyl.
  Firebirds and other GM makes such as the mid 80's
  mid size Delta 88 and similar. The yellow speed
  buffer is usually mounted behind the glove box on
  the passenger side. Be sure to get the connectors
  that go with it.
• I will explain the whole thing as we go along

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Removing the Tail Shaft Cover

• My transmission was already out and on my
  workbench. The 4 red arrows show the bolts that
  you will need to remove to remove the cover.

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Sensors 101

• These are the two speed sensors together. The
  magnetic one (school 1) is on the bottom, and the
  gear driven (school 2) one is on the top. The
  gear driven one is the one that we are concerned
  with now. This simply compares the two of them.

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Gear Choices

• Various replacement gears for the VSS. Pick the
  color that best matches the gear driven speedo
  gear you removed, then use it on the VSS. These
  gears can be had for like 6 or 7 bux. I called
  Mary at Performance Transmission Center in
  Louisiana and she was very helpful.
• HOT TIP!!! A 3.73 ratio will require a
  15 tooth drive gear in the trans, and a 44 tooth
  driven gear. The driven 44 tooth unit is the grey
  one below. This is what I needed and we
  calculated to get the proper speedo reading. You
  will also need the tire HEIGHT.

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4 Output Speed Buffer

• This is a picture of the speed buffer that you
  will need to use to hook this system up
• Make sure that you get as much of the harness as
  possible, it will benefit you in the end when you
  wire things up.

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Wiring Pinout

• The pinout and wiring is shown in the following
  diagram, and the picture on the next page.

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• The main concern with either school of thought is
  to get the speedometer to work. If you can
  accomplish that, then you are gold. My attempt
  will be with the 2nd School, and the gear unit
  and the little yellow 4 out buffer. Seems like a
  good way to go.
• Lets go finish the gear and VSS install on the
  workbench.

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Drive gear removal and installation

• There is a little black clip under the gear that
  must be depressed, then simply remove the drive
  gear from the tailshaft. Installation of the new
  gear is the reverse.

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Sensor In

• The speed sensor will push in exactly like the
  old one came out. The gear will be loose on the
  sensor, but this is normal. Tighten down the 10mm
  bolt, and plug in the wires and this part of the
  job is done!

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This is the old VSS unitThis can be
discardedONLY this end!!!
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This is the other end that plugs into the old
VSS. You will splice these three wires into the
yellow speed buffer to match the colors.
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The buffer revisited

• The remaining wires on the buffer are easy, the
  green is Speedo, the red is cruise, and the
  separate plug with the yellow and purple go to
  the trans sensor.
• Be careful not to run either of these wires near
  spark plug wires or the tach lead, or you will
  end up with the speedo acting like a tach!
• I mounted my buffer under the brake padal on the
  firewall with self tapping screws. Works nicely
  there.

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Fortunately, GM uses mostly the same color wires
in their harnesses between vehicles. In my case,
all I did was re-wire the new plug from the
existing one.

• Its really easy to match the colors.
• Give yourself a little extra wire, you can
  electrical tape the wires together as a loom.
• Test your connections and if all is correct, you
  will get what you will see in the next slide

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Got to love it!

• I like this cluster much more than the other one.
  
• I also installed wedge base illumination bulbs,
  Sylvania 2825. These are rated _at_ 5 cp each.
  Significantly brighter!
• I chose not to install the 2825 lamp in the shift
  quadrantwas just a bit bright, so I substituted
  a 194 bulb there.
• Lets move on to installation

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I forgot

• I mentioned earlier that I installed my yellow
  speed buffer under the brake pedal on the
  firewall. I wanted to clarify that a little by
  showing you how it looks now.

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Center almost done!

• I took the liberty to install and wire up the
  interior light switch, and I added the fog light
  switch.
• The interior light switch has the same color code
  as the old, so simply re-wire to the new
  plugpiece of cake!

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A little bonus!

• Changing out the cable speedo for electronic left
  a nice size hole in the firewall. I simply added
  a rubber grommet and now have a perfect place to
  run wires through

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I love this

• I really love how this looks at night!
• I had the van on my 1955 Hein Werner jack in
  order to do a engine test. I wanted to test the
  Speedo, and it worked!