The Stovebolt Site Forums The Shop Area Driveline 1946 Chevy 1/2Ton - Transmission Speedometer Connector

Last week I started putting fluids in the rear axle, transmission and engine. The transmission leaked a few drops of gear oil. I drained the transmission and added thread sealant on the bolts. I noticed there are some drops of gear oil coming out of the speedometer cable connector - just a few drops each day. Looks like the drops are coming from the middle. Is this normal until I connect the speedometer cable? If not, is this something I can remove and replace a gasket or O-ring?

John, you're doing a better job rebuilding your truck than I could even hope to equal if I ever tried.

It's an 80 year old truck that wasn't exactly hermetically sealed when it was new. A few drops here and there from various orifices is not worth obsessing over.

All I drive and all I've ever driven are antique cars. I've never owned a modern car. They all leak. There are always drips and drops here or there from all sorts of different places. Sometimes they go away on their own. Sometimes they don't. I've just learned over the years that it's more fun driving them than it trying to make them 110% perfect.

I keep cardboard on the garage floor under all of them and add fluids when needed.

I guess it's like owning a British motorcycle. My friend says they always leak. He calls it the slow oil change.

John - In all my searches regarding the speedometer driven gear, it appears to be a factory assembled unit that the gear itself isn't removable from the housing that threads into the transmission. I think once you have a speedometer cable attached, you will see that annoying drip go away. The lube is necessary for the shaft to spin freely inside that housing.

Thanks Dan. Although I do like taking things apart and seeing how they work, I will not remove this. 😊

Hi all. That fitting does come off. It is the speedometer drive that has gears that mesh with the rear transmission yoke. But I wouldn’t bother with it for a leak like yours. Mine is stripped and so are the teeth on the rear yoke so at present I don’t have a speedometer working.

Doug

Agreed Doug that the entire driven gear assembly (gear and housing) comes out as one piece. I think what John was asking is if the gear itself separates from the housing (plug)??? I've searched through everything I can find and can't see where they can be taken apart and if there may be an internal seal involved or not.

Here are pictures of the speedometer driven gear for the GTK-134 four speed non-synchronized transmission. The gear and fitting that holds the gear in place and attaches to the speedometer cable come apart as you can see. There is no seal at all. Notice that one of the gear examples has a spiral groove that acts as an oil slinger. I can tell you that the oil slinger is not that effective and after all, some oil would be needed where the shaft goes through the fitting. I have a damaged gear (also pictured) that does not have the spiral groove, so there is some variability in design.

Bottom line: Tranny gear oil will drip from that area.

Kent

Thanks for posting that picture Kent.

I should also mention that the drive gear, which is pressed onto the u-joint yoke, needs to match the driven gear, shown here above. Sets of gears with different tooth counts allows the same transmission to function correctly with different sized wheels (for example 16' vs 20" wheels). Note that the two gears pictured above do not have the same tooth spacing/count. So you can't just slide whatever driven gear you have into your tranny and expect it to work.

Kent

This is what mine looked like on my 54 with a Muncie 4 speed. It does no come apart as far as can tell. Earlier years seem to come apart so yo can change gear ratios.

Doug

I'm assuming my speedometer will be off since I changed to 3:55 gears. I've seen an adapter you screw on and then screw your speedometer cable into it. I believe the adapter gets calibrated when you order it.

If you hook it up the way it is now, you can calculate the percentage difference that it is off by using a GPS on your phone. When that is known, some sellers have a chart to follow in order to get the exact unit you need. The adapter screws into the transmission and the speedo cable screws into the adapter.

When I get it back on the road, I'll try this GPS method. Thanks Otto!

GPS is a nice thing to have to test speedo readings. A good AP to have on your phone. And yes, when I changed over to 3:55 gearing in back, I had to get an adapter. Different tire sizes affect the adapter.