Perrenial Badass wrote:I'd put my money on the speedo cable having popped out of the back of the cluster.
Can I take that bet? Please? Please can I? How much money are you willing to wager?
And the real answer is....
Transmission fluid is in the cluster and causing a faulty signal.
1984-1986 Analog dash Problem:
Cars have a bad speed indicated (usually reading 100+ while doing 20mph).
Odometer works normally.
Fluid leaking onto floor from under dash (usually on the clutch or gas pedal).
1987-1989 Analog dash problem:
Cars have a bad speed indicated (0mph or way high).
1984-1989 digital dash problem:
Cars have a bad speed indicated (0mph or way high) BUT STILL READING A NUMBER.
Reason:
What's happening is the seals in the pinion gear assembly are bad, so the transmission fluid seeps up the cable and into the cluster. The speed sensor is contaminated, so it sends out a false reading. That's why on the 84-86 analogs, the odometer works correctly, but the speedometer needle swings around like it's a** is on fire.
Briefly:
The only thing you have to replace is the two oil seals.
Everything else is just cleaning and reassembly.
Solution:
- Get the car up in the air.
- Find the speedometer pinion gear assembly at the right rear of the transmission.
- Remove speedometer cable from speedometer pinion gear assembly (if applicable).
- Replace BOTH oil seals (one internal, one external) of the pinion gear assembly.
- 84-86 analog only:
- - Drain speedometer cable of excess transmission fluid.
- - Remove instrument cluster (84-86 analog only).
- - Clean out transmission fluid from cluster.
- - Clean all fluid from all under dash components (steering rack, ducts, etc)
- 84-89 digital:
- - Drain speedometer cable of excess transmission fluid.
- - Clean out transmission fluid from speedometer sensor.
- 87-89 analog:
- - Clean out transmission fluid from speedometer sensor (attached to pinion gear assembly).