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MKI MKII MKIII MKIV

Replacing the speedometer cable on a MkIII Supra
Article# 29

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Category: MKIII _ 1986.5-1992
Subcategory: Manual Transmission
Visited: 18549
Usability Rating: Coming Soon

Article:
Authored by: jlewis@vtc.vsc.edu

Tools Required: 12mm wrench, Crescent or large needle-nose pliers (crescent preferred, locking (Vise-Grip) even better), Philips head screwdriver, Lift or jack stands

Skills Required: Moderate skills

Approximate time: 4 hours
Cost: approx. US$80
Test vehicle: 1987 NA Automatic

Background
The speedometer cable consists of three pieces: the "long" cable, the "short" or extension cable, and the solid "lazy L"-shaped piece that connects to the transmission. This last piece may be different for manual trannies.

The long cable runs from just behind the speedometer through the firewall, behind the engine, and down beside the exhaust to the extension or short cable. The long cable has a squared-off, pointed plastic piece with a two part greenish-yellow plastic shroud on the dashboard end, and a squared metal piece with a screw-on metal shroud where it connects to the short cable.

The flexible extension is about a foot long and accepts the square metal piece in the long pipe on one end, and has a keyed circular center piece with a screw-on metal shroud on the other end that connects to the solid pipe.

The solid piece is very short and sort of L-shaped. It connects directly to the transmission housing via a screw-on metal shroud and a keyed circular center piece. The other end is connected to the flexible extension by the same method (female on this end).

The center piece of each cable spins according to a rate set by the gear in the transmission. This, in turn, spins the speedometer and No.1 speed sensor (inside the speedo).

As far as I know, the gear inside the auto. tranny is not replaceable without tearing down the tranny. If you replace all three parts of the cable and your speedo and things still don't work, you are in big trouble!

Symptoms
Bouncing or completely non-functional speedometer needle.

Other symptoms of a bouncing speedometer:
erratic cruise control
erratic shifting (A/T only)

Other symptoms of a dead speedometer:
non-functional odometer and trip meter
non-functional cruise control
torque converter will not lock (A/T only)
blinking O/D Off light (A/T only)

Diagnosis
Which of the three pieces to replace?

Test long cable.
Disconnect long speedometer cable from short cable (see proc. below). Attach a drill to long cable. Select the reverse direction on the drill. Spin drill slowly. If speedometer does not move or if it bounces at constant drill speeds, replace long cable.

Test short cable
Remove short cable (see proc. below). Spin the center and verify that the other end spins. If it does not, replace short cable.

Test solid pipe
Remove solid pipe (see proc. below). Spin the center and verify that the other end spins. If it does not, replace solid pipe.

Procedure

Replacing the long cable
Use a lift or a jack and jack stands to raise and support the car.

Using the crescent wrench on the long cable and the 12mm wrench to stabilize the short cable, loosen the screw-on shroud on the long cable. Detach the cables.

Detach the long cable from the clip near the long-short cable junction. Detach the cable from the clip in the engine bay near the exhaust manifold.

Using the Philips head screwdriver, remove the console trim, left switch cluster (fog light, cruise, rear defog, etc.), trim beneath the dash, gauge cluster hood, and finally the gauge cluster itself. Take off all the electrical connectors.

Unseat the white clamp holding the cable from the dash by simultaneously pushing inward on the tabs and pulling up. Remove the clamp from the cable.

Remove the long cable by pulling on the cable in the dash, either from the gauge cluster hole or from beneath the dash. If it sticks, push the cable through the firewall from the outside. You may have to use a screw driver to force the rubber grommet around the cable through the firewall.

Feed the new long cable through the firewall from the inside. Get out and pull the rest of the cable through.

Connect the new cable to the two clips and reconnect it to the short cable with the crescent and 12mm wrenches.

Reseat the rubber grommet in the firewall.

Feed the other end of the cable up to the gauge cluster opening. Reconnect the plastic white clamp, and seat the clamp in place.

Carefully replace gauge cluster, taking care not to break the new cable. Replace all trim.

Disconnect negative battery terminal for several minutes to clear errors codes from the ECU.



Replacing the short cable

Use a lift or a jack and jack stands to raise and support the car.

Disconnect the long and short speedometer cables.

Locate the place on the transmission where the solid pipe screws in. It will be above the exhaust pipe, just before the catalytic converter or resonator. Using locking pliers, grip the solid pipe shroud and turn it counter-clock-wise. Remove the pipe with the short cable still attached.

Detach the solid pipe from the short cable.

Bend the short cable approximately in the shape of the old cable. Install the new short cable.

Reinstall the hard pipe (with short cable attached) to the transmission using pliers to tighten, making sure to orient the short cable so that it is pointing toward the long cable.

Reconnect the long and short cables. You may have to unclip the long cable in the engine bay to provide some slack.

Seat long cable in both clips.

Disconnect negative battery terminal for several minutes to clear errors codes from the ECU.



Replacing the solid pipe

Use a lift or a jack and jack stands to raise and support the car.

Disconnect the long and short speedometer cables.

Locate the place on the transmission where the solid pipe screws in. It will be above the exhaust pipe, just before the catalytic converter or resonator. Using locking pliers, grip the solid pipe shroud and turn it counter-clock-wise. Remove the pipe with the short cable still attached.

Detach the solid pipe from the short cable.

Install new solid pipe on the short cable.

Reinstall the hard pipe (with short cable attached) to the transmission using pliers to tighten, making sure to orient the short cable so that it is pointing toward the long cable.

Reconnect the long and short cables. You may have to unclip the long cable in the engine bay to provide some slack.

Seat long cable in both clips.

Disconnect negative battery terminal for several minutes to clear errors codes from the ECU.

My experience

My speedo went dead about three days after I got my Supra (150,000 miles when I bought it). I did a bit of research, and after *much* screwing around I managed to get parts about a month and a half after it broke. I went through a friend who works at a Toyota dealer. I got a good discount, but Jeff Watson's prices are probably better and shipping is probably faster. :)

When I took apart my dash (before I got the parts), I noticed the plastic end of the long cable was still stuck in the speedometer! So, I knew that I would have to replace this cable. I told my friend to order all three parts of the speedometer cable, since I didn't want this to happen again. Total cost was about US$75.

I first replaced the long cable, because that was the only part that I knew was broken. By far, the most difficult part was re-seating the rubber grommet in the firewall. I probably spent two hours doing this. There is almost no room to get your hand in behind the valve covers to playing with the grommet. I finally gave up with it about halfway seated, and wrapped some electrical (black vinyl) tape around it and called it done.

I got in my car expecting to have a speedo and cruise (which I really missed), but it still didn't work. I think that it is possible that I broke the long cable when I took the dash apart, and that the real problem was somewhere else. I was already late for work, so I had to drive 100 miles with no cruise and no speedo. :(

After I got home from work, I jacked up the car to have a look at the short cable. I couldn't even see where the short cable connected to the pipe, or where the pipe screwed into the tranny. The tranny support brace and exhaust are really in the way. I gave up, thinking that I would stop by a shop with a lift and have them do it. I slept on it.

I woke up feeling optimistic, so I checked my service manual to locate where the speedometer connects to the tranny. The manual that I have is for an 86.5 Supra (mine's an 87), and it doesn't have a procedure for changing the speedo cable. But, in the section for removing the tranny, it does show a picture of a car with the exhaust and manual shifting lever removed, exposing the speedo cable attachment, just behind the tranny brace.

I went out and jacked up my car to have a look. After much searching and running back to the service manual, I found the connector on the tranny. I could just reach it with a pair of pliers. First, I tried simple crescent pliers, which had no hope. The cable was on there really tight. So, I tried a set of big pipe-grabber pliers. They have really big teeth, and grabbed really well, but all they did was smooth off one side of the cable shroud. As a last resort I tried a pair of Vise-Grips (locking pliers). I put them on as tight as a dared, and they spun off. After much swearing and a couple of cigarettes, they caught and loosened the cable shroud.

I was very confused when I pulled the pipe off the tranny, because instead of seeing the keyed center piece, I saw a short piece of cable sticking out of the tranny with something else still in there. I pulled it out, and it turned out to be the center piece of the hard pipe! Apparently, the cable had broken in the middle, and they keyed piece was still stuck in the tranny. After some finagling with needlenose pliers, I pulled it out.

Re-installing the new pieces was a breeze. Apparently, you don't have to line up the keyed parts with the parts inside the tranny, because mine slid right in. No problem.

After a victory smoke, I went for a spin and everything worked again. I had cruise, speedo, trip meter and odometer, and my torque converter was finally locking up again! It was actually a new experience for me because the speedo bounced really bad when I bought the car before it finally broke. Now it is as smooth as silk.

Thanks to Pete Sterling for cluing me on a bunch of things when I first thought of tackling this project. He provided lots of advice, like which direction to spin the drill and other important stuff. :)


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