Ranger519v

O.k., I've been reading numerous threads on various speedo gear issues but I can't find my answers so I'm looking for help on my '64 roadster.

I have a new cluster and have done a reverse drill test of my cable back to my cluster - nice steady speedometer reading. However, when I hook cable to speedo housing in the tranny - I get nothing. I noticed transmission fluid around the speedo housing so I pulled out speedo housing/gear and noticed the o-ring is pretty shot. However, the 21 tooth red driven gear looks to be in perfect order! I've not dropped my tranny so I can't see the drive gear.

In looking at the configuration of housing/driven gear, I can't tell if something is missing that should retain the driven gear in the housing? Something that would also keep the transmission fluid from flowing along the driven gear shaft and into the speedo cable. When I pulled my housing, the driven gear fell easily out the back. If some sort of bushing is suppose to be there, mine is missing. Might this also help in keeping the driven gear pressed against the drive gear?

Before I took all apart 2 years ago, my speedometer was bouncing but I believe that was due to dry cable. I now have new cluster, speedometer, and cable but the housing, speedo gear, and transmission are original. When all hooked up, I get nothing.

Any leads would be appreciated! If I'm missing a bushing, would love a photo if someone has one handy! If I'm not missing a bushing, what keeps the transmission fluid from leaking past the driven gear shaft?

magicv8

If the edges of the speedometer gear teeth have any visible wear, replace the gear. In my experience, when the meter needle bounces, the gear needs to be replaced. In the last 20 years my car has gone through 5 gears with the same cable and one speedometer rebuild. The gears are cheap.

If you have good O rings on the cable adapter, and it fits snuggly in the tailshaft bore, there shouldn't be a problem with it.

wombvette

The gear has no retainer. The action on the gear pushes it into the housing.

midyearvette

..also, there is a reversed groove on the shaft to push the fluid back...check your drive gear with a small screwdriver to see if it is loose on the mainshaft....good luck.....

JohnZ

The later speedo gear adapters had a rubber internal seal to keep trans lube out of the cable (see photo below), and they're interchangeable with the early style that didn't have the seal; all the vendors have the later style.

Ranger519v

JohnZ, thanks for the pic.

Went to a very reputable tranny store and was able to pick up a complete housing WITH bushing. Put in my 21 tooth red gear (in perfect order) and re-installed in the tranny. Went in smooth and easy. Went for a test drive hoping to have speedo register and NOTHING

I guess there must be something wrong inside the tranny (or my 21 tooth isn't compatible)? I have no idea what it takes to drop the tranny to get to the internal drive gear?

Ideas?

nassau66427

Have you tried using a real small screwdriver in the end of the driven gear to see if you can turn it? It shouldn't turn.

You can inspect the drive gear with a mirror and flashlight.

To access the drive gear you need to pull the transmission and remove the tailshaft.

If you go this far, you might as well replace the tailshaft bushing while you are at it.

Ranger519v

Nassau,

I'll try the small screwdriver insertion later tonight. I'll also see if I can find a dental mirror to see within. Thanks for the leads and I'll post a follow-up as soon as I get under there again.

Ranger519v

Well, it failed the screw driver test - driven gear turns freely when the housing is seated. Using a mirror, the metal drive gear is there and appears to be in perfect shape.

Going by the archives, sounds like I might have the wrong driven gear (too small a diameter?)? How do I go about determining what tranny I have, what drive gear would be in it, and what driven gear I should have? Though I'm learning a ton and willing to tackle anything (even if I have to drop the tranny), this is a new area for me.

Ranger519v

Doing the "tire turn and count axle rotations" trick that JohnZ and others have described, I believe I have a 3.70 rear end (11.1 axle turns for 3 tire rotations). And then looking at the tables (again, thanks JohnZ), it looks like both sizes of drive and driven gears were used in the 3.70. So I'm going to assume that is has the small drive gear and the current (red) driven gear is too small in diameter. I will order the 22-tooth green driven gear and keep my fingers crossed.