I have a '65 with HEG-T 3-spd tranny and 2.75 rear end. My speedometer drive gear is worn out (I'm the 3rd gen driver of this, my grandpa's truck - nobody can every remember it working). I've been cruising the forums here and I think I have learned that the part number for the gear is C3OZ-17285-C. However, I also saw a part number of D7TZ-17285-A for a 4-SP trans that had the 2.75 rear end. Other than the number of teeth, will the D7TZ work? I priced the C3OZ at the local dealer and was told it would cost $78. Found some other "metal" gears being sold for $99. OUCH!

 

The speedometer drive gears are likely specific to a particular transmission type. I would think the 4 sp. drive gear would not work on your three speed. I am not sure tho. Perhaps try the transmission, axle forum also.

 

Just to make sure we know what you're after...the transmission has a drive gear and the speedometer cable has a driven gear. The teeth on the driven gear are plastic and are interchangeable to accomodate different tire sizes and, more importantly, different differential gear sets. If you pull the driven gear from the transmission, what color is the plastic? I just went from a 3-speed manual circa 1966 to an AOD from 1993 and the speedo driven gear was a direct plug-in with the driven gear being the only swap to get the ratios correct. I still have a driven gear (can't remember what tooth count) but if that's the one your looking for you can have it. They are only about $13 new.

 

RaleighDad is right, you can get by much easier by changing the plastic driven gear at the end of the speedometer cable. They are cheap new, and are plentiful at the boneyards.

I would first check your driven gear, to make sure it is the problem. If the plasitc teeth are chewed up, then you know what the problem is. If they look good, then the problem may be in the speedometer cable or in the speedometer itself.

When you remove the driven gear (the one on the end of the speedometer cable), look on the face for some numbers - that will be the tooth count. Also notice the color, as the color usually indicates the tooth count as well.
Replace your existing gear with one which has the same tooth count for similar speed indications.

Look for a matching one from a boneyard next time you visit. They come in brown, pink, white, cream and green - and maybe more. Make usre the teeth on the used one you choose are not chewed up, either.

To replace the gear, first remove the speedometer cable by unscrewing the retaining bolt, and popping the cable and retainer out of the transmission. Next, pull off the clip at the back of the gear, which holds it onto the cable. Then pull the gear off.
Installation is the reverse.

By the way, if you put in taller gears in the rear axle for better mileage or speed, such as going to a 2.75 from a 3.50, you will need to use a speedometer driven gear with FEWER teeth.
If you put in a gear ratio for more power, such as going to a 4.11 from a 3.50, you will need to put in a speedometer driven gear with MORE teeth.

 

I'm in need of the drive gear (the one in the transmission - not the end of the cable). The reason I need it is the one I have has been ground away to nothing through the years. My first attempt to repair the speedo was the driven gear swap, but there's nothing wrong with it. I have the engine out for a swap to 390, so I pulled the transmission to look inside - sure enough, the gear is worn away completely. I pulled the gear and took it to the local ford parts store (two of them actually). Neither of them could even come up with a number. The numbers I list in my original post are numbers I've gathered from this forum. I think it was Barry who listed the C3OZ-17285-C part number that sounds right for my original setup (with 3.5, I think). That's what I'll go with if nobody has any suggestions for alternate parts (due to cost mostly).
TIA

 

Well, who says you need a new part?
If that is an original Ford 3 speed light duty transmission, there are a bazillion of them out there. You could probably get a replacement transmission a whole lot cheaper from a boneyard.
Or, you may be able to find a transmission in pieces from the boneyard, and get the used shaft even cheaper.
Just some ideas.

 

I found some sources for that gear.

Dennis Carpenter 1-800-476-9653 25 in stock

Jasper L-M Jasper, Tx 1-409-384-3411 1 in stock

LaPoint Ford Murray, Ut 1-801-264-4800 1 in stock

Bell-McCall Hamilton, Mt. 1-406-363-2011 1 in stock.

Call them and give them the part number, don't mention what it fits, to them it's just an old part and you'll get a decent price.

Barry