Speedo Gear help

Ok I tried and failed as a Ford parts guy so I need help
I looked into why the speedo was not working in the truck and found the drive gear in the transmission is stripped, driven gear looks good.

Here is what I found but I cant tell if right or not as nothing lines up with what I have.
Truck is a late 80 with a T18 transmission with a 2.75 geared 9”
Drive gear looks to be white in the truck, Driven gear is white also looks to be type 2a.

 Based on the documentations the drive gear being white is listed as
12 / 7 types?       11392 ID       D3TZ 17285 – A   part number

Now when I look up the drive gear for 80 under “Drive Gear Combo” the white is for a 4x4 T/C and it only list the 2.75 rear gear with a 3/speed?

So we go to 81 (and 82) “Drive Gear Combo” look up the rear gear ratio and 4 speed and come up with a brown gear C80Z 17285 – B
So should my truck have this brown gear C80Z 17285 – B installed and if so can it be used with the white type 2a driven gear?

That brings up the next can of worms for the white driven gear on the cable in the truck.  
2a type,  17 teeth,  C3DA  17217 – B  ID #,  green or white color,  C3DZ 17271 – C part #

I cant even find my transmission till I am in the 3.xxgear ratios! How does this all work?????
And forget about part numbers or ID numbers I cant find them.

Here is a picture of the cert. sticker so you can see the both transmission & rear gear used.

So what do I need to get this speedo working again? just get a white drive gear and it will work or get both and know they will work together?

And to stir the pot some I have the SROD transmission from the parts truck that I can use some or all the parts if they will work.

If they will not where could I get the needed parts?

Thanks
Dave ----

I think we are going to have to limit the number of issues or questions that can be broached in one post.  

I can't my head around all of those!  

Ok, let's try this.  If you go to the Driven Gear Part #'s tab you'll see that for whatever reason Ford didn't put the 2.75 axle behind a T-18, aka 4MT.  So you have an oddity.  But, if you scroll down to the 3.25 axle ratio you start to see the 4/M/T.  And that tranny takes a C80Z 17285-B which is a 8-toothed gear.  And if you go look at any of the 4/O/D transmissions, which would include the SROD, you'll see that they don't use that drive gear.

As for a driven gear, the right one for the 3.25 ratio are C0DD-A, or -B, or -C, or C1DD-A depending on tire size.  And if you scroll back to the top of that tab you'll see that those are 2A's in the 16, 18, 19, or 20 tooth form.

But you don't have a 3.25 axle.  Instead you have a 2.75 axle.  And here the plot thickens as we have to know the tire size in order to get there.  So, if you'll give me your tire size I'll see what I can do to get the driven gear figured out.

I thought I did post it
I think I did in my draft and it got left out in the final copy

The tire size on the truck is 235 / 75R / 15
Truck came with 215 / 75r / 15 from the factory as per the sticker so just a little bigger.

So it looked like I did have the right drive gear brown from the list.
Don't know how a white got in the transmission?

Ok so I was not crazy (don't answer that )
That they did not list the gear ratio I have and why I posted the cert label.
so I did need to go to where the ratio was listed to find it.

Thanks for the help.
Dave ----

Just looked over the driven chart and see it would be B or C gear.
Now to hit Ebay to see if I can find any.
Thanks again
Dave ----

FuzzFace2 wrote

The tire size is 235 / 75R / 15 truck came with 225 / 75r / 15 from the factory as per the sticker so just a little bigger.

215/75/15 as per the Certification Labels above.

Ok, let's try this: If you look at the 2.75 axle ratio chart you'll find that an E100/350 w/a 3-speed manual tranny, meaning 1:1 top gear like your T-18, and 235/75 tires had an D7TZ 17285-A drive gear and a C0DD 17271-B driven gear.  That's a 8-toothed drive gear and a 16-toothed driven gear.  In other words, they want a 1:2 ratio.

So if you go with C80Z 17285-B, which is an 8-toothed drive gear you'll want a 16-toothed driven gear.  And that's C0DD 17271-A which is wine colored.

Note that I'd do the same calc on the F100/350 but it takes C2DZ 17271-F and I can't find the tooth count for it.

Ok so I ordered the drive gear  C80Z 17285-B based on the what your first post said and listed.
And if I under stand right I need driven gear C0DD 17271-A, C0DD 17271-B, C0DD 17271-c or C1DD 17271-A to match to the drive gear.

Now to have the speedo read right I need a 16 tooth driven gear on the C0DD 17271-? type.
Would the gear set below work as it has the 16 / 17 / 18 tooth gears for less that I can get just the
C0DD 17271-A / 16 tooth gear for and have the other for fine tuning if need be.

https://www.ebay.com/itm/Ford-Speedo-Drive-GEARS-Set-of-3-NEW-NOS-OEM-Mustang-speed-transmission/141735123921?epid=1240632031&hash=item2100125bd1:g:ST8AAOSwoi1X82jM
Thanks for all the help
Dave ----

Rembrant wrote

FuzzFace2 wrote

The tire size is 235 / 75R / 15 truck came with 225 / 75r / 15 from the factory as per the sticker so just a little bigger.

215/75/15 as per the Certification Labels above.

Cory cant you read it lists 215

After I posted I proof read and found the wrong size and changed it before I saw your post but thanks


Man it's the little things now that makes you pull your hair out.
Good thing a have a lot right now
Dave ----

Yes, that set should work just fine.  

Gary Lewis wrote

Yes, that set should work just fine.  

Thank you for the help both gears have been ordered.
This 3 gear set said by 12/4/19
Dave ----

Welcome.  Happy to help.