I have a 1967 Cutlass Holiday Coupe with the 2 speed auto trans. The gear that drives the speedometer is shot. Does anyone know how many teeth that gear should have so I can order a new one?

Thanks!

 

The correct gear depends on the rear axle ratio and tire outside diameter. Without that information your question cannot be answered.

 

I still have no idea what the rear end gear ratio is. However, I do now know that I have a 39 tooth gear in the transmission that drives the speedometer that is completely worn out. I have a replacement arriving any day now. Once I have replace the gear, I will check the speed using my GPS to see if I am close.

 

Before you button up the gear in prep for your road test, spin it as fast as you can by hand while someone watches to see if the speedo needle jumps off of zero. Also, the gear and cable should turn freely rather than springing back. This test will ensure your speedo or cable is not bound up. If bound up, the gear will probably be toast again after the test drive, or the cable will break.

 

Great advice Ragtop. Unfortunately, I have a more difficult issue. When I popped out the retainer and old worn out gear, I noticed that the gear on the trans shaft could not be seen. I did some feeling around along the shaft and was able to move it back into an area that looks right. However, I have no idea where it is supposed to be along the shaft or what is supposed to hold it in place. I guess I will be dropping the drive shaft this weekend and removing the trans tail.

 

I'm going to do an "assume" here, that the drive gear on your 2-speed is held on in a similar way as it is on a TH350 -- i.e., with a clip. Someone please confirm, or correct me if I'm wrong. Here's a YouTube video showing the TH350 drive gear install:


As you stated, in order to get in there you'll have to remove the driveshaft and then the tailshaft housing (4 bolts). If the transmission mount is on the tailshaft housing you'll have to undo that as well after jacking up the trans slightly. While you have the tailshaft housing off it's always a great idea to replace the driveshaft yoke bushing and seal. Although the following video has almost as many thumbs down as it does thumbs up - and it's on a TH400 - it shows you the basics of how to do this:


More questions? Fire away...

 

Hey Ragtop, your assumption is absolutely correct. I found a clip that looks just like the one in the first video just hanging out in my trans tail. I suspect getting it all back in place will be a bit harder with the car lifted and the trans still installed, but , at least, I know what to look for now.

Thanks!

 

Another question on the same subject.

Should there be transmission fluid in that tailshaft housing section of the transmission, or does finding trans fluid in there mean that my Drive Shaft Yoke bushing and seal is in need of replacement?

Thanks in advance.

 

Trans fluid splashes into the tailhousing in normal operation. That's why there is a seal on the yoke - to prevent that fluid from reaching the outside.

 

Agreed. The fluid kinda casually gets in there, then gravitates back to the pan.