Cable or Gear?

[RTStabler51]

Forgive the possible stupid question, but all my cars so far have had electronically controlled speedos.

Is there a way to tell if the speedo cable is bad or the gear in the trans? Someone told me the gear in the trans is plastic...is that true?

My speedo broke at the track day, I'm assuming from a couple of hard downshifts and over revvin the engine a bit.

[SVOeric]

first pull the instrument cluster.
then jack up the rear wheels with jackstands.
start the car, drop it in 2nd gear
watch the speed-o cable, does it turn ?
Don't drive too far, , cause the car won't charge with the cluster out.

if the cable isn't turning, your problem is deeper (cable or gear)

[BrianO]

I've had this happen before with two different causes..

1. cable got too close to my headers and burned through it, speedo no work.
2. the teeth on the driven gear sheered off, speedo no work.

[RTStabler51]

Thanks for the info guys.
so, even if the gear is broken, it sounds like a semi 'easy' fix? In searching I read a post that talked about removing the tailshaft of the trans. Did I miss something on that one?

[SVOeric]

if it's the cable, or the gear on the end of the cable, it's an easy fix.

If it's the gear inside the trans, on the tail-shaft, it's not an easy fix.

[cometcyclonemk]

So my speedometer is out as well. Pulled the cable, the gear on it looks good, it spins freely and when you spin it the speedo moves... So it pretty much has to be the gear in the tranny right? How big of an undertaking is it?

[BrianO]

you have to remove the drive shaft and remove the tailhousing of the tranny and it will be right there.

[SVOinDC]

If you have to pull the tranny let me know, I want to come and watch / hand you tools so I can learn how to do it-

Cheers!
Chuck

[BrianO]

^
Not quite.

I was assuming a bit.. figured most knew the tranny had to come out.

[RTStabler51]

Looks like its the gear on the end of the speedo. Anyone have a PN for it?

I think I have answered my own question, but would like confirmation from the SVO Gurus
Using this sheet it looks like I want the 'wine' colored gear part number CODZ17271A. Is that true?

[GAboySVO]

Last time I had my speedo cable out, I counted 19 teeth on the driven gear.

[cometcyclonemk]

If you have to pull the tranny let me know, I want to come and watch / hand you tools so I can learn how to do it-

Cheers!
Chuck

Well I've never pulled the tranny / torn it apart either... So unless we can find someone to show us both how to do it I think I'll be running without a speedometer for a while... At least until I get a ticket...

[RTStabler51]

Replaced the speedo gear and the cable...still no worky. Looks like the internal gear needs replaced. :-(

[gbeaird]

The gear on the trans output shaft is steel, IIRC. It is, however, held on by a little flimsy spring clip, that apparently can easily come loose. That's what's happened to our 86. The drive gear has slid back on the output shaft so that it no longer contacts the speedo gear. I'd check this and see if that's what happened to you. If so, as others have indicated, the trans needs to come out and the tailshaft housing pulled.

If the drive gear is centered in the hole for the speedo gear, check to verify it is still firmly attached to the tailshaft. Your clip may have some out, and the gear is just spinning on the tailshaft.

Additionally, I think I had the speedo cable come loose at the cluster once. I failed to verify the lock locked into place. You may want to check there before climbing under the car.

Gene Beaird,
86 2R SVO, G Stock,
Pearland, Texas

[RTStabler51]

The gear on the trans output shaft is steel, IIRC. It is, however, held on by a little flimsy spring clip, that apparently can easily come loose. That's what's happened to our 86. The drive gear has slid back on the output shaft so that it no longer contacts the speedo gear. I'd check this and see if that's what happened to you. If so, as others have indicated, the trans needs to come out and the tailshaft housing pulled.

If the drive gear is centered in the hole for the speedo gear, check to verify it is still firmly attached to the tailshaft. Your clip may have some out, and the gear is just spinning on the tailshaft.

Additionally, I think I had the speedo cable come loose at the cluster once. I failed to verify the lock locked into place. You may want to check there before climbing under the car.

Gene Beaird,
86 2R SVO, G Stock,
Pearland, Texas

Gene, that's where I'm at and narrowed it down to the trans gear. My fear is that its just slide off. I don't have the facilities to yank the trans out myself. I could put it up jack stands and do it, but my patience is lacking right now so I'm just gonna git-r-done right. She does to the local doctor on Saturday.