Hello everyone. Hope all are doing well. a funny thing happened about a month ago. I was taking the truck to a function at a voctech school for a demonstration. It was cold, but the truck in in my garage. It was not heated that day. Only heat it when I'm working out there. there was a weird noise coming from the dash. the speedometer was bouncing around then pegged to the right. then stopped. I am assuming that the gear or something broke. question # 1. WHAT DO YOU THINK IT CAN BE? #2 how do we fix it? thanks guys. 1954 f-750. My fire truck

 

could be a broken cable, when it pegged to the right then stopped, did it go back to 0 ?

 

thank you for responding. to my knowledge, it stayed to the right. I can not see if it is still pegged or not.

 

It's the cable. Its all twisted up inside . BEtter to just order the cable and shroud/ coax toghethor.

 

thanks guys. I will get on it tomorrow. I'll let you know how it goes. Love this place

 

Not a expert on these but just had a bunch of speedos apart and I think there is a magnet type drive that as the cable is spinning it lifts the needle off the peg. If the cable stops moving the needle returns. If yours is stuck to the right my guess is it's in the head itself. You can hook your cordless drill to the back of speedo and run it slow ( can't remember if cw or ccw)

 

thanks Greg, Here is the way the needle moves, I am gonna get out there today and see If I can determine where the needle is. https://www.engineersedge.com/instru...l_movement.htm

 

Hi gang. went out to the truck, disconnected spedo cable. Jacked truck up on blocks, put it in gear. cable definitely broken. then I took cluster out to see If I could turn by hand with a small square bit. No dice. the unit is frozen solid. I removed spedo mechanism from cluster. It does not look like anything is replaceable except the whole mechanism which includes the needle, face plate,odometer numbers and the movement . any good leads on a replacement.

 

I'm wondering if it's ever been lubed up since you've had the truck. Hear me out. My '56 speedo is original to the truck. My truck sat in a field for 20 years before I brought it home. So you can bet the speedo gears had not been lubed in a very long time. I went through two speedo cables before I realized that something was wrong. So I took mine apart and found the gears and all to be really rusty and caked with junk. My speedo wouldn't budge. With some poking and prodding and then using white lithium grease I freed it up. It now works really well. I wouldn't doubt that the noise you heard was the speedo cable winding and twisting in the sleeve. Before you get too concerned take the cluster apart and have a good look. They're pretty tough.

 

Calvin. thanks for the reply Here is what I have. I'm looking into the cluster. Looks clean, but something is frozen

 

This is what I'd expect, the bearings on the drum are bad and allowing the magnets to touch it. No practical way to repair at home, but someone like United Spedometer can. May be available NOS too.

 

Ross, thanks for the input. I'll be looking around for replacements. Always great hearing from you Jim G

 

Hi Jim! Glad to see you on the forum. Not wishing you bad luck on you Truck though. Any interested buyers for your truck? If I'm not mistaken, I also thought that you were also moving? Hope all is well and you get your speedo figured out Dave

 

Put the drill in reverse to make the speedo go up in mph's.

 

Inside the speedometer cable housing is a woven steel core that is supposed to be lubed every so often, but most people are unaware.

When the lube dries out (originally it was white lithium grease), the woven steel core binds up inside the housing, eventually snaps.

Auto parts stores sell a 'universal' woven steel core kit, you cut it to length, coat w/a fine film of graphite (better than the grease) and install it in the housing.