Frustrating Foxbody Speedo

[Mustang5L5]

Well the driven gear I bought is white and it’s 17 teeth. I used the calculator on lmr. 3.08 gears in rear end with 245-45-17 tires. The transmission I’m told is a world class t-5 so I think the drive gear is supposed to be 7 teeth.

Based on that info, you should need a 7 tooth drive gear.

All T-5's in the Mustang from 1985 through 2010 were world class. Ford changed from the 7 tooth to the 8 tooth after 1990. Unsure what gear the aftermarkets had.

You can just tell by color.
Black = 6 tooth
Yellow = 7 tooth
Green = 8 tooth.


Regardless, I think you have all the info you need to diagnose your issue.

 

[Keith5.0GT]

Based on that info, you should need a 7 tooth drive gear.

All T-5's in the Mustang from 1985 through 2010 were world class. Ford changed from the 7 tooth to the 8 tooth after 1990. Unsure what gear the aftermarkets had.

You can just tell by color.
Black = 6 tooth
Yellow = 7 tooth
Green = 8 tooth.


Regardless, I think you have all the info you need to diagnose your issue.

Yes thanks for the pictures and kicking around ideas with me. Easy to understand how the gears work now. I appreciate it.

 

[Keith5.0GT]

Based on that info, you should need a 7 tooth drive gear.

All T-5's in the Mustang from 1985 through 2010 were world class. Ford changed from the 7 tooth to the 8 tooth after 1990. Unsure what gear the aftermarkets had.

You can just tell by color.
Black = 6 tooth
Yellow = 7 tooth
Green = 8 tooth.


Regardless, I think you have all the info you need to diagnose your issue.

Ok I figured it out. Luckily the drive gear is fine. Although I could get the speedo needle to twitch spinning the cable by hand, when I attached the cable to a dremel,(fit perfectly) it doesn’t work! So do you know of a repair method or do I have to buy a unit off eBay? I don’t see any repair kits or new speedos for sale so far. Thanks

 

[Mustang5L5]

Are you confident the cable is making a secure connection to the back of the speedo head? Sometimes those aftermarket cables never really fit well, or fall out when you are trying to push the cluster back in.

 

[Keith5.0GT]

Are you confident the cable is making a secure connection to the back of the speedo head? Sometimes those aftermarket cables never really fit well, or fall out when you are trying to push the cluster back in.

Well I have 2 good cables now and neither work in the speedo head. I do hear a noise from back of speedo head when I spin cable. So tomorrow I should have time to take it apart again and I’m hoping that the connection has just become slightly rounded or something I can fix myself. I’ve read there are magnets involved with the needle that can get messed up too. But I’ll definitely have a look when I get it apart. I read another guy on here got an eBay replacement and used it for parts to fix his, so that’s an option too. Just hard to find on any forum where anyone has repaired a speedo head. But I’ll look tomorrow eve and post what I find.

 

[Keith5.0GT]

Are you confident the cable is making a secure connection to the back of the speedo head? Sometimes those aftermarket cables never really fit well, or fall out when you are trying to push the cluster back in.

Well I have 2 good cables now and neither work in the speedo head. I do hear a noise from back of speedo head when I spin cable. So tomorrow I should have time to take it apart again and I’m hoping that the connection has just become slightly rounded or something I can fix myself. I’ve read there are magnets involved with the needle that can get messed up too. But I’ll definitely have a look when I get it apart. I read another guy on here got an eBay replacement and used it for parts to fix his, so that’s an option too. Just hard to find on any forum where anyone has repaired a speedo head. But I’ll look tomorrow eve and post what I find.

 

[General karthief]

Pm me you prodution date and I'll check my stash tomorrow.

 

[Mustang5L5]

If you spin the speedo head by hand, it doesn't take much to spin it up to 20-40mph or so

 

[Keith5.0GT]

Pm me you prodution date and I'll check my stash tomorrow.

Ok thanks. Where would I find the production date? It’s a 1990

 

[General karthief]

Look on the left side where the door striker is, or when you pull the dash get me the part number from the wire print board.

 

[Keith5.0GT]

Look on the left side where the door striker is, or when you pull the dash get me the part number from the wire print board.

Ok, my car has had door jambs painted in the past so I don’t have stickers there unfortunately but I’ll check the part when I get it off this evening. Thanks

 

[General karthief]

I would prefer the print board number

 

[Keith5.0GT]

Well I got it apart. I double checked the speedo unit and I can get the needle to move. So I have the rear end lifted and I can idle in first and the speedo cable end in the dash isn’t spinning....even though I was able to put in gear with cable and rotate tires to verify that it would spin. So I’m jus baffled. It’s obviously in the trans at the moment but the gears are there and they did work by hand. Something is going on but I don’t know what. Poop

 

[Mustang5L5]

Smear some lithium grease in the teeth of the speedo drive gear and install it. Turn the rear wheels so the trans nainshagt spins.

Pull the speedo gear out again and see if the grease you packed into the gears is displaced because it's making full contact with the drive gear

 

[Keith5.0GT]

Smear some lithium grease in the teeth of the speedo drive gear and install it. Turn the rear wheels so the trans nainshagt spins.

Pull the speedo gear out again and see if the grease you packed into the gears is displaced because it's making full contact with the drive gear

Ok I may have it figured out! It’s the part that’s not supposed to be the problem, the vss! I spin the driven gear and the cable doesn’t move. Take the gear off and spin the shaft of the vss, nothing. It won’t spin the inserted speedo cable no matter what. So where the cable fits into the vss, something stripped out or broke and that’s it! It’s got less than 2,000 miles on it so I’m buying a motorcraft vss this time. I’ll let ya know if it works but I know that’s it now.

 

[Keith5.0GT]

Ok I may have it figured out! It’s the part that’s not supposed to be the problem, the vss! I spin the driven gear and the cable doesn’t move. Take the gear off and spin the shaft of the vss, nothing. It won’t spin the inserted speedo cable no matter what. So where the cable fits into the vss, something stripped out or broke and that’s it! It’s got less than 2,000 miles on it so I’m buying a motorcraft vss this time. I’ll let ya know if it works but I know that’s it now.

UPDATE finally;
Got a motorcraft vss, and yes that fixed the speedo. But the cable was extremely hard to insert. After inserting it, there was more resistance when turning the driven gear, which resulted in a jittery speedo needle. Long story short, my new speed cable was maybe, 1/4” too long, causing the cable to bind and needle to jump. Once I finally shaved enough off the cable where the driven gear had no resistance, I had a smooth speedometer again. Hooray. Onto the next problem

 

[General karthief]