Speedometer... WTF?!

[loglat]

Need some help on this one...

My speedometer on my 69 F100 doesn't work... at all. When I first bought it, the needle would bounce around a little, sometimes it worked, but most of the time it didn't. Later, it stopped working altogether. I replaced the cable, and nothing changed. The gear looked a little worn, so I replaced that too. It still does nothing. When I turn the speedo gear with my hand, the needle moves, but when I plug it into the tranny... you guessed it: nothing. Everything inside the transmission seems intact. I can feel the gear that drives the cable, and it doesn't feel loose, or like it's missing any teeth or anything (dont know why it would be, but I thought I'd throw that in there).

Anyway... I'm out of ideas on this one. What the heck is wrong with my speedometer? It's driving me nuts!!

[fordman]

if turning the plastic gear makes the speedometer work then the gear isnt contacting the metal gear in the transmission. or the metal gear is spinning on the shaft and it isnt turning the plastic gear.

[flyboy71]

Replaced cable.... check
Replaced gear...check
You spun the tranny gear by hand underneath and the speedo moved up top? or did you spin the back of the speedo itself?

Only other piece missing is whether you drove the truck with the cluster out to see if the tranny was engaging the cable and spinning it.

Otherwise something is badly worn somewhere and when you connect it together its slipping.

[loglat]

I turned the plastic gear by hand, and it made the needle move. If the gear in the transmission was spinning on the shaft, I'd think i could turn it a little by hand, but thats not the case. I've bolted the cable into the tranny and left the instrument cluster out, and the end of the cable doesnt move... I guess it HAS to be a problem with the transmission, but what if anything can i do about it?

[fordman]

something else i just thought of. the plastic gear comes in two different lengths. maybe you bought the short one when you needed the longer one.

[thunderbolt]

I had the exact same issue, it was the drive gear inside the transmission that was spinning. New transmission, speedometer works like a champ! (i didn't replace it because of that, just happened to fix it)

[loglat]

Where can I get the longer speedo gear??

[fordman]

from any of the vendors on the links page.

[loglat]

One thing I didn't mention that may be important... My truck now has an NP-435. There are too many gears to choose from... i understand the tooth count bit, but there are diff TYPES of gears that supposedly "fit" my truck. Same with the cable. Seems like it should work, but it doesnt! Argh!

[fordman]

http://www.lmctruck.com/icatalog/fb/t.aspx?Page=46 page 47 style number 2. is suppose to fit 4 speed transmsisions.

[loglat]

Hmm... I can't tell the diff between the two on that page, but the one I have in it now looks more like style number one. I was ready to order about 10 different kinds and try them all out... still may. Gotta get this thing working!