speedo out of whack - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

theman · 07-15-2003, 00:21

Driving through the burbs today and i went past one of those speed checker things, anyway as i approached it at about 58-60 (on my speedo) it read about 47, then when i slowed down to about 50 (on my speedo) it read 42

.
Is there a way of changing/fixing the speedometer yourself, if so how and where on the car. Or where is a good place to get it done CHEAP. tnx.

07-15-2003, 00:30

Yeah, there is a speedo gear in your auto/manual transmission under the car that you can change the gearing for depending on your diff. If you get under the car you will see a connector with 2? Wires coming off it, and 1 bolt holding it in.

Take that out, then go to this website:
http://forums.fordmods.com/phpBB2/documents.php?doc=30

and then using their calculator work out using the colour of your old one and the speed, what new colour gear you need to get from ford. And remember you need a HIGHER gear then what you currently have. For example if it's 3.08, you will probably need a 3.23 gear from ford, etc etc.

AUForte · 07-15-2003, 01:49

I trust those speed checkers as far as I could throw them. Have yous speedo checked but it may not be out.

07-15-2003, 02:37

The fordmods one is pretty accurate, and it shows you all the speedo ratio's and the corresponding colours for them so you can't go wrong. Also you can check out the diff ratio which can be found on the side of the diff, but it can be hard to find, and get the corresponding speedo gear for it.

AUForte · 07-15-2003, 03:22

I'm talking about the speedo checkers on the side of the road, also the overhead ones, drive past a few and the reading at each one will be wildly different.

Doesn't give me much confidence

theman · 07-16-2003, 01:53

For the speedo calculator thing, how am i supposed to know what diff and tyre size was originaly used on the car?

07-16-2003, 20:07

The diff ratio is marked on the diff itself on the side. But you can just use the speedo gear out of the transmission by comparing it to the colours on the website. Remember your actual diff ratio will be higher then the speedo you have, thats why it's showing the incorrect speed.

By the sounds of it, you have a 2.77 Purple-19 speedo gear in there, and have a 3.23 or a 3.45 ratio diff.

What type of car is it you have?

Pull the speedo gear out, and then compare the colour to the ones on the link.

theman · 07-16-2003, 21:10

I have an EA Fairmont, Oct 1988. I'll have to take the gear out on the weekend when i'm not using the car so i don't burn myself.
Whilts checking my diff to see what sort it was (i couldnt see anything indicating it's ratios), i noticed that the breather tube on the rear axel is snapped off. Is this a big issue or not, i'm going to get the car serviced soon by the guy who replaced the diff for me (i had it replaced about 2 months ago), so i should get him to fix it.

Thanatos · 07-16-2003, 23:20

Quote:

Originally Posted by AUForte

I'm talking about the speedo checkers on the side of the road, also the overhead ones, drive past a few and the reading at each one will be wildly different.

Doesn't give me much confidence

I remember there was a big fuss a while ago about how innacurate these things are! I wouldn't trust it at all!!!

Dave

PHoeNiX_EB · 07-17-2003, 03:32

I defenetly wouldnt trust those dam things. Especially the older ones. I went through one on the other seide of the city once. I was in the Left lane doing 110 and I was being overtaken by a 4wd in the right lane. My Speed read 112 and his 104 Yet he was overtaking me. Get a professional to check it.

PHoeNiX_