I am having a bear of a time trying to remove the fitting that holds the plastic gear for the speedometer cable in the transmission.  I have already removed the retainer.  I have tried unscrewing this thing, and prying it out, but no luck. 

Does anyone have any insight on how to get this thing out?

Are you talking about the plastic housing that fits in the trans?
They can sometimes be a pain. Spray around the outer perimeter with WD40(or whatever) first. Tap IN on it gently with a small hammer/plastic/rubber mallet. Then use a large pair of pliers, or channel locks to twist it as you pull out on it. You may need to push it in/out a little as you go. They usually don't like to be pulled out crooked, so keeping it straight in the hole will help. That's why you need to tap it in first, to get it straght.
hth
Adams' Apple2010-12-15 06:00:44

[QUOTE=Adams' Apple] Are you talking about the plastic housing that fits in the trans?
They can sometimes be a pain. Spray around the outer perimeter with WD40(or whatever) first. Tap IN on it gently with a small hammer/plastic/rubber mallet. Then use a large pair of pliers, or channel locks to twist it as you pull out on it. You may need to push it in/out a little as you go. They usually don't like to be pulled out crooked, so keeping it straight in the hole will help. That's why you need to tap it in first, to get it straght.
hth
[/QUOTE]

Wow!  Thanks for the tip, it popped right out.  Unfortunately the gear was perfect.  I cleaned everything up, put it back together, and I took it out for a spin.  The speedometer jumped between 0 and 10 at first, stayed at 10, then I went over a bump and the gauge is dead again.  I think I may need to have it rebuilt.  I hooked it up to my drill last night and it was making some grinding noises, but it worked up to 100 miles per hour. 

Did you look at the gear inside the trans? If the speedo is bouncing, it's possible the gear on the shaft is loose, or otherwise damaged. If the little clip is gone/damaged, it can cause the speedo to bounce around like that, and maybe work one time, and not the next.
If the speedo head itself(dash gauge) is making noise, you need to determine if it is in fact a noise IN the head, or the cable making noise....


btw...I'm assuming this is an automatic trans?
Adams' Apple2010-12-15 20:53:08

I didn't really pay too much attention to the gear inside the transmission, but the section that I did see looked ok.  I did not check to see if it was loose.  If it is loose, is there anything I can do about it without having to take the transmission apart?

Where is this little clip that you mentioned? 

The cable should be ok, it is a brand new cable.  I should mention that there is a 90 degree elbow between the cable and gear.  I tested it out while I had everything apart, and it turns easy. 

Also, it is the original 4 speed manual transmission.

Ah HA!
The 4 speeds had a 90deg adapter that is actually a reducer. There is a gear set inside there that can cause problems, also. If the speedo works spinning it with a drill, but doesn't with it connected to the trans, and the trans gears are ok, then that leaves the reducer/adapter as the culprit.

Being a 4 speed, it's gonna be dang near impossible to look up in there and see the drive gear...unless you have really tiny eyeballs...or a borescope. The four speeds do NOT use a clip to hold the drive gear...it is pressed onto the shaft. They do get loose, tho it is rare for that to happen. My bet is on either the adapter/reducer, or the speedo head itself, at this point.

The speedometer does work when I spin it with a drill, but it is making some rather horrible noises and seems inconsistent in the speed displayed. 

My guess is the speedometer as well, but I may pull off the adapter tonight and have another look at it, and try spinning it with the drill as well.

Thanks for all your help, this is my first Corvette and the first car I have done all the work on myself, so your advice has been really helpful.

May have some doo-doo(high tech term) up in the speedo magnet/coil that is making the noise, and causing the speedo to be erratic...

On a very closely related matter (I don't THINK I'm hijacking the thread), my various manuals are silent on choosing the correct colour speedo gear to match the particular differential gear fitted.  Assuming the same tyre diameter as stock (which mine has, despite the very wide wheels/tyres fitted at the rear), is there available a 'matching chart'?  I believe my car has the AM code / 3.36 rear.

The parts manual has a breakdown of available gears for each year, sorted by trans, and diff ratio. It does specify colors on the gears, also.
I could look it up if ya want...it'll take a while, since finding stuff in the parts manual is tedious....and I'm lazy.

SOME 4 speeds may not have an adapter/reducer. I believe some of the earlier Muncies had the speedo on the driver side of the tailhousing, instead of the pass side, as the BW trannys do. The parts manual also states whether or not a given trans/diff/speedo gear combo requires a reducer/adapter, and what ratio it would have if needed....