I Need Gear/Speedometer Help
Postmaster
Joined: Aug 2005
Posts: 2,760
Likes: 8
From: Gadsden Purchase
Mine was out of range and a gear wouldn't correct it. :)
IMO you guys are making this thing too complicated.
-time your speedometer
-pull the gear out, count the teeth
-do some math (post it, I'll do the math?;)
-find out if a gear is actually made the size you need {shrug}
Timing it might find your speedometer is faulty?
Does a C6 lock up 1:1 in third gear?
Different brands of tires are different sizes, enough to matter?
Alvin in AZ
IMO you guys are making this thing too complicated.
-time your speedometer
-pull the gear out, count the teeth
-do some math (post it, I'll do the math?;)
-find out if a gear is actually made the size you need {shrug}
Timing it might find your speedometer is faulty?
Does a C6 lock up 1:1 in third gear?
Different brands of tires are different sizes, enough to matter?
Alvin in AZ
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
Likes: 785
From: Simi Valley, CA
The tire sizes originally used in the 1970's are all that are listed in the 1973/79 parts catalog.
There were no P-Metric radials available till years later.
I have no clue what a 315/75-16 tire size would be compatible to the tires used in the 1970's.
C1DZ17271A .. 20T Speedometer Driven Gear / Color Coded Black / Available from Ford.
MSRP: $3.07 // FTEpartsguy.com price: $2.21.
Application: 1975/79 F250 / New Process 435 4 Speed / 4.10-1 / 6.50" x 16" tires = See what I mean.
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Alvin, Ford said: The difference of one tooth of the DRIVEN gear is between 7 to 10 MPH, depending on the application.
Senior User
Joined: Dec 2007
Posts: 118
Likes: 1
From: Colorado
Bill I see what you mean, it makes sense that Ford would only show specs for factory tires. I do know my 315/75-16 tires are equivalent to 35" tall tires, I don't know how tall 6.50" x 16" tires are. If I could figure out the height difference and knew which way (more or less teeth) on the driven gear to go I could probably get it close. Speedo gears are cheap and easy enough to change that I could make an educated guess and not worry if I were wrong. Thanks Bill for the input.
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
Likes: 785
From: Simi Valley, CA
Bill I see what you mean, it makes sense that Ford would only show specs for factory tires. I do know my 315/75-16 tires are equivalent to 35" tall tires, I don't know how tall 6.50" x 16" tires are. If I could figure out the height difference and knew which way (more or less teeth) on the driven gear to go I could probably get it close. Speedo gears are cheap and easy enough to change that I could make an educated guess and not worry if I were wrong. Thanks Bill for the input.
Check with a local tire store, they have charts that interchange tire sizes between then...and now.
Senior User
Joined: Dec 2007
Posts: 118
Likes: 1
From: Colorado
For everyone's info, this is where I found the formula for speedo gear sizing:
Speedometer Gear Color Code Specification Chart With Formulas, And Ford Part Numbers. - Page 4 - Ford Explorer Ranger Enthusiasts Serious Explorations
This forum has some good info on it.
Speedometer Gear Color Code Specification Chart With Formulas, And Ford Part Numbers. - Page 4 - Ford Explorer Ranger Enthusiasts Serious Explorations
This forum has some good info on it.
Thread Starter
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Senior User
Joined: Nov 2008
Posts: 153
Likes: 4
From: Utah
NumberDummy... I tried the 19T tonight and I believe it WAS even further in the wrong direction.
Alvin... I timed a mile at fifty seconds (that means 72MPH according to your chart). My speedometer read 57MPH.
1ole4d... I can't find anything about gear reducers on the internet, but then again, I'm not much good with computers either.
Everybody... I have to apologize and embarass myself. Tonight, I noticed that according to the tag on my door, I ACTUALLY have a C4 tranny.
Now, I'm assuming I'm still out of options as far as replacing the cheap and easy driven speedo gears. I asked around town on my deliveries to shops today and found that there's no one left in my area that can calibrate a speedometer. Does that leave me with the only option being replacing the output shaft with the drive speedometer gear? What options are there for that?
Needless to say, I'm a driver, NOT a mechanic.
Thanks guys for being patient with me so far.
Alvin... I timed a mile at fifty seconds (that means 72MPH according to your chart). My speedometer read 57MPH.
1ole4d... I can't find anything about gear reducers on the internet, but then again, I'm not much good with computers either.
Everybody... I have to apologize and embarass myself. Tonight, I noticed that according to the tag on my door, I ACTUALLY have a C4 tranny.
Now, I'm assuming I'm still out of options as far as replacing the cheap and easy driven speedo gears. I asked around town on my deliveries to shops today and found that there's no one left in my area that can calibrate a speedometer. Does that leave me with the only option being replacing the output shaft with the drive speedometer gear? What options are there for that?
Needless to say, I'm a driver, NOT a mechanic.
Thanks guys for being patient with me so far.
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
Likes: 785
From: Simi Valley, CA
NumberDummy... I tried the 19T tonight and I believe it WAS even further in the wrong direction.
Alvin... I timed a mile at fifty seconds (that means 72MPH according to your chart). My speedometer read 57MPH.
If you reduce your present driven gear by two teeth, the speedo will read between 71 and 77 MPH.
Back then, most speedo's were in-accurate by at least 5 MPH. Ford said that one tooth of a driven gear would add or subtract between 7 to 10 MPH, depending upon the application.
Adding teeth slows down the speedometer reading, subtracting teeth speeds it up.
Tonight, I noticed that according to the tag on my door, I ACTUALLY have a C4 tranny.
YOU DO NOT!
Now, I'm assuming I'm still out of options as far as replacing the cheap and easy driven speedo gears. I asked around town on my deliveries to shops today and found that there's no one left in my area that can calibrate a speedometer. Does that leave me with the only option being replacing the output shaft with the drive speedometer gear? What options are there for that?
Alvin... I timed a mile at fifty seconds (that means 72MPH according to your chart). My speedometer read 57MPH.
If you reduce your present driven gear by two teeth, the speedo will read between 71 and 77 MPH.
Back then, most speedo's were in-accurate by at least 5 MPH. Ford said that one tooth of a driven gear would add or subtract between 7 to 10 MPH, depending upon the application.
Adding teeth slows down the speedometer reading, subtracting teeth speeds it up.
Tonight, I noticed that according to the tag on my door, I ACTUALLY have a C4 tranny.
YOU DO NOT!Now, I'm assuming I'm still out of options as far as replacing the cheap and easy driven speedo gears. I asked around town on my deliveries to shops today and found that there's no one left in my area that can calibrate a speedometer. Does that leave me with the only option being replacing the output shaft with the drive speedometer gear? What options are there for that?
(sigh)
Your truck DOES NOT have a C4 transmission! Where the heck did you come up with that malarkey?
It's a C6.
No V8 F250 on the planet ever came with a C4! Some 1965/72 F250's with 240 I-6's used C4's.
The Warranty Plate TRANS code is G.
From 1960 thru 1978, Ford used that SAME fracatta G code for ALL automatic transmissions on car/truck Warranty Plates, regardless of what A/T it was.
This means that G stood for a: Ford-O-Matic, FX or MX Cruise-O-Matic, FMX Cruise-O-Matic, C4, C6 or even a JATCO = Japanese Auto Trans Co. This trans was used in some Ford taxi-cabs.
Back then, one had to know which A/T came with which engine. There was a Ford ID tag on all A/T's which when decoded told exactly what it was.
Most partsguys/mechanics could eyeball an A/T and know exactly which one it was.
1979 was the first year Ford used a specific code for the C6, which was the letter K.
C4 = 11 transmission pan bolt holes / The C6 has 17.
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Thread Starter
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Senior User
Joined: Nov 2008
Posts: 153
Likes: 4
From: Utah
ACH du LIEBER!!
(sigh) Your truck DOES NOT have a C4 transmission!
Where the heck did you come up with that malarkey?
It's a C6.
No V8 F250 on the planet ever came with a C4! Some 1965/72 F250's with 240 I-6's used C4's.
The Warranty Plate TRANS code is G.
From 1960 thru 1978, Ford used that SAME fracatta G code for ALL automatic transmissions on car/truck Warranty Plates, regardless of what A/T it was.
This means that G stood for a: Ford-O-Matic, FX or MX Cruise-O-Matic, FMX Cruise-O-Matic, C4, C6 or even a JATCO = Japanese Auto Trans Co. This trans was used in some Ford taxi-cabs.
Back then, one had to know which A/T came with which engine. There was a Ford ID tag on all A/T's which when decoded told exactly what it was.
Most partsguys/mechanics could eyeball an A/T and know exactly which one it was.
1979 was the first year Ford used a specific code for the C6, which was the letter K.
C4 = 11 transmission pan bolt holes / The C6 has 17.
(sigh)
Your truck DOES NOT have a C4 transmission! Where the heck did you come up with that malarkey?
It's a C6.
No V8 F250 on the planet ever came with a C4! Some 1965/72 F250's with 240 I-6's used C4's.
The Warranty Plate TRANS code is G.
From 1960 thru 1978, Ford used that SAME fracatta G code for ALL automatic transmissions on car/truck Warranty Plates, regardless of what A/T it was.
This means that G stood for a: Ford-O-Matic, FX or MX Cruise-O-Matic, FMX Cruise-O-Matic, C4, C6 or even a JATCO = Japanese Auto Trans Co. This trans was used in some Ford taxi-cabs.
Back then, one had to know which A/T came with which engine. There was a Ford ID tag on all A/T's which when decoded told exactly what it was.
Most partsguys/mechanics could eyeball an A/T and know exactly which one it was.
1979 was the first year Ford used a specific code for the C6, which was the letter K.
C4 = 11 transmission pan bolt holes / The C6 has 17.
Thanks, Ryan.
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
Likes: 785
From: Simi Valley, CA
I will have a parts guy at a local dealer decode the plate (I'll take it off the tranny and drive it in to the shop) so he can get me the right output shaft then.
You are wasting your time, because that trans code won't tell you diddly squat.
I can't reduce any more teeth from the driven gear because I already have the 16T and they don't get any smaller, right? Right.
You are wasting your time, because that trans code won't tell you diddly squat.
I can't reduce any more teeth from the driven gear because I already have the 16T and they don't get any smaller, right? Right.
When you go to parts list A70.4 there are two different output shafts listed for your application.
But the code plays no part in pointing to which output shaft you have now.
You have to know what the present tooth count is on the output shaft.
E2TZ7060A replaced: D6AZ7060A .. Output Shaft / 6 Teeth / Obsolete
KINSEL L/M in Beaumont TX has ONE = 800-816-2894.
FRED GRANDE FORD in Richmond MI has ONE.
BOB ALLEN FORD in Overland Park KS has ONE = 800-676-0675.
HAVEN FORD SALES in Haven KS has ONE = 800-748-7803.
PARTS INTERNATIONAL in Farmers Branch TX has ONE = 888-727-0418.
No other Ford dealer or obsolete parts vendor has any.
-----------------------------------------------------
E2TZ7060C replaced: D6TZ7060B .. Output Shaft / 8 Teeth / Obsolete
ED BENNETT OBSOLETE FORD PARTS in Lebanon PA has ONE = 717-272-8762.
No Ford Dealer or other obsolete parts vendor has any.
Thread Starter
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Senior User
Joined: Nov 2008
Posts: 153
Likes: 4
From: Utah
Well guys, I found a place that can calibrate my speedometer... it should get done this week and it's cheaper than replacing an output shaft. What makes it even better is that it's the last thing my truck needs to be done. Thanks for your help.
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