I have a 97 Expy, E40D and 5.4. I've been trying to figure out how to change my speedo back to stock since moving up to a slightly larger tire size. Many here said it's a simple speedo gear change but the dealership doesn't show a speedo gear in my tranny; just an entire electronic assembly. Others here say its a computer program change that is easily done at the dealership.
I recently had 2 different Ford mechanics tell me 2 different answers; 1 says gear, the other says electronic. Since my speedo needle goes to zero when I turn off the ignition while moving I figured it was electronic. I made an appointment with the dealer to get it reprogrammed and they confirmed it to be a simple $50.00/45 minute program change.
After 1hr 45mins in the waiting room I go back to check on the progress. Service writer says that their new scan equipment can't enter the new program so they called Detroit who told them to use an "old style" scan tool and it would work. 45 mins later I'm told that my truck can't be reprogrammed and that it needs "the gears in the transmission changed". The parts department doesn't show any speedo gear in my tranny. This is really starting to "p*%!" me off. Apparently even the guys in Detroit don't know how to change it. I can't believe people aren't getting their speedos adjusted on '97-'98 Expeditions. Is my Expy different than an F-150?

 

I don't know if there were any difference's in the trannies for an Expie or an F150, but my tranny is the E40D (TR code "E" on door jamb.....) When I went to larger tires, I just swapped out the VSS gear. As I understand it, if you have the digital odometer, you have the electronic, computer programed setup. If it's just the plain old dial type, then it uses the gear.

The VSS is an electronic device itself. But, it uses a small plastic gear to drive the unit. This should be located on the tail shaft part of the tranny at the top. It's held in place with a single nut and just pulls out when removed. There is an "O" ring and you should make sure all dirt is removed from the area before removing.

My stock gear was a 20 tooth (black) gear. I went to 265/75/16's and had to go to a 19 tooth (I think it's tan in color....) gear to bring back to normal. Cost about $10.00 from the Ford Parts counter and about 5 minutes of time under the truck...........

 

Thanks Mitchf150...
My odometer is analog and they (dealership Parts and Service dept.) still said it needed the reprogram...Go figure.
The parts dept showed me an assembly that enters from the side of the tranny on the drivers side of the tailshaft. The assembly was about 4-5 inches long. My tranny has this part up above the center line; high like you say. You're saying that when I take this out I will be able to remove the speedo gear and replace it right? Does this assembly need to be disassembled or is the speedo gear still in the housing after the assembly is removed? Did your parts dept. know what you were talking about when you showed them the gear?
This little project is making me feel stupid. I thought I was saving time and headache by assuming the dealer guys were smarter than I was. I guess a person still can't beat the old tried and true method of figuring it out ourselves.
Thanks again.

 

Yeah, when you pull out the unit, the gear is attached to it. I think it had a small "C" clip that held the gear on the shaft...... Just pull it out, remove the gear, put new gear on, replace clip and put back in. Make sure it's seated properly and tighten the little nut.

When I bought the gear from the parts counter, I just asked for the "tan 19 tooth one"...... Explained that it was for the VSS unit and he looked it up on the computer. Showed me an exploeded view of it, and I said "That looks like the one" (I had already removed it once just to see what the stock gear was and looked like.)

He came back with one and counted the teeth and it had 19 of them, so that's what I used.

It's been in for over two years now and not a problem.

 

I pulled the VSS and found out what the gear looked like. Found a Ford dealer that had a listing of the speedo gears according to stock R&P and tire size. They had 2 different styles of 20 tooth and the one I needed was the black one. Thanks.

 

got it. it was a 20 tooth black gear.thx.

 

Is there a way to figure out what gear I would need using either 285/70/17 or 315/70/17? Thanks, Greg

 

The dealer only had factory gear ratio/tire speedo gear combos listed. The other way would be to go to the Miata tire calculator website (type that into a search engine) and punch in your factory tire size compared to your new tire size and it will give you the percentage difference in size. If it says 10% larger then you could check with the dealer for a gear 10% smaller than stock. The dealer told me that a single tooth change on the gear accounts for 4 mph change. Good luck.

 

The dealer only had factory gear ratio/tire speedo gear combos listed. The other way would be to go to the Miata tire calculator website (type that into a search engine) and punch in your factory tire size compared to your new tire size and it will give you the percentage difference in size. If it says 10% larger then you could check with the dealer for a gear 10% smaller than stock. The dealer told me that a single tooth change on the gear accounts for 4 mph change. Good luck.

 

The dealer only had factory gear ratio/tire speedo gear combos listed. The other way would be to go to the Miata tire calculator website (type that into a search engine) and punch in your factory tire size compared to your new tire size and it will give you the percentage difference in size. If it says 10% larger then you could check with the dealer for a gear 10% smaller than stock. The dealer told me that a single tooth change on the gear accounts for 4 mph change. Good luck.

 

The dealer only had factory gear ratio/tire speedo gear combos listed. The other way would be to go to the Miata tire calculator website (type that into a search engine) and punch in your factory tire size compared to your new tire size and it will give you the percentage difference in size. If it says 10% larger then you could check with the dealer for a gear 10% smaller than stock. The dealer told me that a single tooth change on the gear accounts for 4 mph change. Good luck.

 

The dealer only had factory gear ratio/tire speedo gear combos listed. The other way would be to go to the Miata tire calculator website (type that into a search engine) and punch in your factory tire size compared to your new tire size and it will give you the percentage difference in size. If it says 10% larger then you could check with the dealer for a gear 10% smaller than stock. The dealer told me that a single tooth change on the gear accounts for 4 mph change. Good luck.

 

The dealer only had factory gear ratio/tire speedo gear combos listed. The other way would be to go to the Miata tire calculator website (type that into a search engine) and punch in your factory tire size compared to your new tire size and it will give you the percentage difference in size. If it says 10% larger then you could check with the dealer for a gear 10% smaller than stock. The dealer told me that a single tooth change on the gear accounts for 4 mph change. Good luck.

 

The dealer only had factory gear ratio/tire speedo gear combos listed. The other way would be to go to the Miata tire calculator website (type that into a search engine) and punch in your factory tire size compared to your new tire size and it will give you the percentage difference in size. If it says 10% larger then you could check with the dealer for a gear 10% smaller than stock. The dealer told me that a single tooth change on the gear accounts for 4 mph change. Good luck.

 

The dealer only had factory gear ratio/tire speedo gear combos listed. The other way would be to go to the Miata tire calculator website (type that into a search engine) and punch in your factory tire size compared to your new tire size and it will give you the percentage difference in size. If it says 10% larger then you could check with the dealer for a gear 10% smaller than stock. The dealer told me that a single tooth change on the gear accounts for 4 mph change. Good luck.