Speedometer correction
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Posting Guru
Joined: Oct 2004
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Yeah, I believe that my gear would be the right helix one. My 20 tooth gear is black though, I haven't seen any that are black. I read on that site that " I believe that reproductions of the driven gears are only available in black." What does that mean? My drive gear is light green i believe, or light blue. Its one of those i know. I don't know if that can lead to anything though.
What would happen if my ratio's were different? I don't seem to have any problems in 4WD.
What would happen if my ratio's were different? I don't seem to have any problems in 4WD.
Post Fiend
Joined: Mar 2004
Posts: 24,418
Likes: 3
From: San Francisco, Ca.
You mean if the front and rear differential were different?
That could be a problem.
I don't know much about 4x4s.
My original gear was neutral color at 17 teeth.
Now I'm using a black (20 teeth).
I take it for granted you're not the original owner?
You could always mark the sidewall of the rear tire with a piece of tape , turn it and see how times the driveshaft turns, just to make sure you do have 3.55 or what ever you have. Just to see if indeed you have 3.55s
That could be a problem.
I don't know much about 4x4s.
My original gear was neutral color at 17 teeth.
Now I'm using a black (20 teeth).
I take it for granted you're not the original owner?
You could always mark the sidewall of the rear tire with a piece of tape , turn it and see how times the driveshaft turns, just to make sure you do have 3.55 or what ever you have. Just to see if indeed you have 3.55s
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Yeah, what would happen if the front and rear were different? Would I be able to tell just by driving it, or would it be subtle but destructive?
No, unfortunatly I am not the original owner. I will have to try out that little trick tomorrow. I am curious to see if I do still have the 3.55. Can I do the same thing with the front, to see if they are still the same? Would the front be 3.55 as well, or is there some different ratio that it would be?
No, unfortunatly I am not the original owner. I will have to try out that little trick tomorrow. I am curious to see if I do still have the 3.55. Can I do the same thing with the front, to see if they are still the same? Would the front be 3.55 as well, or is there some different ratio that it would be?
Post Fiend
Joined: Mar 2004
Posts: 24,418
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From: San Francisco, Ca.
I pretty sure you can try that same trick on the front.
I think the ratios for both front and rear should be real close. I think give a ponit or two.
You mentioned that you did a mileage check with a mileage marker on the road.
You were two-tenths off, right?
So your odometer read .8 mile instead of the full 1 mile, right?
I think the ratios for both front and rear should be real close. I think give a ponit or two.
You mentioned that you did a mileage check with a mileage marker on the road.
You were two-tenths off, right?
So your odometer read .8 mile instead of the full 1 mile, right?
Thread Starter
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Correct, .8 miles instead of 1 mile.
I am as certain about my drive gear as can be. I checked it twice before, then today I have checked it probably 3 more times. I drew a crude picture of what I am seeing. Its in my gallery. Am I counting the teeth right? I am trying to take pictures of it with my digital camera, but I am having a hard time getting the whole thing at once through the little hole.
Another thing that I am having problems with is counting the revolutions of my drivetrain and tire to check my rear end ratio. I do what I am supposed to do according to several posts, but my drive line is only spinning about 1 3/4 per tire revolution.
I am as certain about my drive gear as can be. I checked it twice before, then today I have checked it probably 3 more times. I drew a crude picture of what I am seeing. Its in my gallery. Am I counting the teeth right? I am trying to take pictures of it with my digital camera, but I am having a hard time getting the whole thing at once through the little hole.
Another thing that I am having problems with is counting the revolutions of my drivetrain and tire to check my rear end ratio. I do what I am supposed to do according to several posts, but my drive line is only spinning about 1 3/4 per tire revolution.
Post Fiend
Joined: Mar 2004
Posts: 24,418
Likes: 3
From: San Francisco, Ca.
Here's a site that tells you how to check the ratio, but it's written poorly.
http://zhome.com/ZCMnL/tech/WhatRearEndRatio.htm
That 1.75 sounds off. Did you have both rear wheels off the ground?
If you're off by .2 of a mile, that's 20 %, which is damn close to the 83%.
It does sound like a 17 tooth driven gear is what you need.
Just for ha-ha's, maybe check out the site too see what ratio you have.
http://zhome.com/ZCMnL/tech/WhatRearEndRatio.htm
That 1.75 sounds off. Did you have both rear wheels off the ground?
If you're off by .2 of a mile, that's 20 %, which is damn close to the 83%.
It does sound like a 17 tooth driven gear is what you need.
Just for ha-ha's, maybe check out the site too see what ratio you have.
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Post Fiend
Joined: Mar 2004
Posts: 24,418
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From: San Francisco, Ca.
I wonder if I'm reading that site correctly. It says to multiply the number of rotations by 2.
If that's the case, then you have 3.5 ratio (or 3.55)-1.75 times 2.
Sounds like to me, 17 tooth driven gear.
I think what they're saying (on that site) is to rotate the wheel 10 times, just to be a bit more accurate. They say rotate 10 times, and then devide by 10.
Personally, it sounds like you have a 3.55.
17 tooth gear. See if Ford has one. Bet they're cheap.
If that's the case, then you have 3.5 ratio (or 3.55)-1.75 times 2.
Sounds like to me, 17 tooth driven gear.
I think what they're saying (on that site) is to rotate the wheel 10 times, just to be a bit more accurate. They say rotate 10 times, and then devide by 10.
Personally, it sounds like you have a 3.55.
17 tooth gear. See if Ford has one. Bet they're cheap.
Post Fiend
Joined: Mar 2004
Posts: 24,418
Likes: 3
From: San Francisco, Ca.
Yep, that is strange that the calculators were that much off.
I'd see if Ford has that gear and how much.
Just make sure it's the correct helical type.
Maybe a speedo service shop may have that gear or can tell you what or where to get one.
You know, you may have a drive gear other than 7 in there.
I know it's pretty hard to accurately count the gears while inside the trans.
Either way, I'd take a gamble and get the 17t gear.
But that's me.
I'd see if Ford has that gear and how much.
Just make sure it's the correct helical type.
Maybe a speedo service shop may have that gear or can tell you what or where to get one.
You know, you may have a drive gear other than 7 in there.
I know it's pretty hard to accurately count the gears while inside the trans.
Either way, I'd take a gamble and get the 17t gear.
But that's me.
Senior User
Joined: Dec 2002
Posts: 105
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From: Salem, Oregon
Speedometer correction
I had to replace the drive gear in the transfer case; worn out. Then the odmeter was right on but the needle read about 5mph fast. I found an adjustment lever in the speedometer itself. Works sort of like a watch spring. Getting it zeroed 
in now. I found the parts I needed from Drivetrain.com out of Vegas. Ford dealers just wanted my credit card. No help at all.
in now. I found the parts I needed from Drivetrain.com out of Vegas. Ford dealers just wanted my credit card. No help at all.
Last edited by webster; Nov 19, 2005 at 11:40 AM. Reason: more info...
