Where to Get Speedo Gear in Transfer Case and..?

[Mikey]

...how difficult is it to change? I'm referring to the gear in the transfer case, not on the speedo cable. Is it plastic? Do I need to drain out the fluid to change?

Let me know.
Thanks,
Mike

 

[DirtDonk]

It's been awhile so I could be wrong, but I remember it being a steel gear sandwiched between other components on the output shaft. So you would have to remove the rear output assembly and take it apart, at least to a certain extent.
What happened? Is yours stripped or damaged? That would be unusual from what I've seen since the driven gear is soft plastic and the drive gear is very hard steel. Hope it's not damaged though since I imagine it's a junkyard part or a specialty item that some of the vendors might have.
Obviously the dealer would be a source IF they still have any laying around. Maybe a Jeep specialty supplier since the Dana 20 was used in some Jeeps too. Maybe the Dana 18 used the same piece too?
Good luck. Hopefully someone else will have a happier answer for you.

Paul

 

[Mikey]

Hmmmmm....My speedo is not working at all. I rebuilt the gauge itself and then would spin the cable to check operation. Needle would flicker. Speedo cable gear looked good so I stuck my pinky in the transfer case to check the gear. Heck, it felt like it might be stripped but really couldn't tell. If it's steel, I'm sure that's not it. Now, I'm stumped.

I currently get no speedo reading at all. It used to flicker once in awhile a couple of years ago but nothing now. Been sticking with flow of traffic and sound of engine. ;D

Any help would be...er...helpful!
Thanks,
Mike

 

[DirtDonk]

Hey Mike, I had almost the same problem once. My plastic gear didn't look stripped, but the center section of it was worn down just enough to only engage the drive gear some of the time. Even though the gear was smooth, looking at it closer revealed that it had sort of a half-moon shape in the center so it didn't work right. A new gear solved the problem.
BUT, speedo cables are notorious for failing inside the casing too. I never did get mine out because I didn't want to pull the casing out of the firewall and the bend kept my inner cable from pulling out all the way, but I did manage to spray some slimy cable lube stuff in there with the help of one of those motorcycle cable luber attachment thingies and haven't had any trouble in years.
Hope you find your problem.

Paul

 

[DirtDonk]

Oh, and can you tell whether or not your drive gear spins inside the transfer case? I may be wrong, but I seem to remember that it's not actually pressed on the shaft and that it is round inside. No splines or flats or keys to keep it from spinning. Only the pressure of the adjacent components pressing into it from either end. So, if something was wrong with your output shaft assembly, could the gear spin on the shaft? I don't know but it's just a wild guess to throw out to the others.

Paul

 

[don parris]

spedo gears

I had the same problem with my 77 and when I pulled the housing off the rear of my transfer case the gear was worn down to almost nothing it. was plastic" I called jeff at bronco graveyard and he sold me a used steel gear and matching driven gear. the drive gear uses shims to keep it from spinning on the output shaft

 

[DirtDonk]

Interesting about the plastic inner gear Don. Seen (and replaced!) plenty of them on NP203's, but haven't been inside but a few Dana 20's so I've only seen the steel ones.
So I guess that means you should take a real close looky-loo inside your case Mikey. Don't know if you can get up high enough with a flashlight to see in the hole, but it's worth a try.

Paul

 

[COBlu77]

It's real simple. No need to take apart the T-case. Just follow the speedo cable to where it attaches to the D20 and you'll see a bolt (7/16" I think). Undo the bolt and the small plastic speedo gear (approx 3/4" diam.) comes right out. I bought several at the local Ford dealer (about $6.99 each), so I could see which one was right. I used my GPS to check speed against the speedometer. One of the easiest, cheapest and most usefull upgrades I've done. Even if you have to go back for a different sized wrench, it won't take 5 min..

They are color coded. (New Gear/Old Ratio X New Ratio=New Gear).
16 tooth gear Ford #C0DZ17271 A (purple)
17 tooth gear Ford #C3DZ2-17271 C(white)
18 tooth gear Ford # ?? (yellow
19 tooth gear Ford#C0DZ-17271 B(pink)
20 tooth gear Ford#C1DZ-17271 A(black)
21 tooth gear Ford #C4OZ-17271 A(red)

 

[Mikey]

I guess I'll take a very close look at the gear on the cable. May even change it regardless. I can't see how the gear in transfer case could be worn down and not the cable gear whether it's plastic or metal. I shouldn't trust the feel of my pinky tip.

I'm running 31 inch tires with 3.50 gears. Which gear should I get?

If the cable is broken inside the case, wouldn't it just not work and not flicker if I spin the gear by the transfer case?

As best as I can tell, the failed item is either the cable, gear on the cable or the gear in the transfer case. If I remove the gear/cable out of the transfer case and spin the gear with my fingers, the speedo needle will flicker. Gear on cable does have the clip on it like it's supposed to. Only checked the transfer case gear by squeezing my pinky in and trying to feel if there were teeth. There are but if feels a bit worn. Not sure. May have felt the blood in my finger tip as it was turning purple! Perhaps I need to grab a mirror to look in. Probably better to by a brand new gear on the cable side first and try that as it's the easiest and needs to be changed anyway to match my tires. Everyone agree?
Thanks for your help!!!
Mikey ;D

 

[pinenuts]

Here is something I copied off an earlier post that might help:
-----------------------------------------------------------------------------
Changing tire size or gears will throw off your speedometer. This is annoying, but easy to fix by changing the speedometer gear in the transfer case.
Step 1: Find out how far off your speedo is.
Drive on the highway for 10 miles (according to mile markers) and note how far your odometer advances. Divide the odo reading by 10 and that will tell you what percentage your speedo is off.

Example: If you drive 10 miles and your odometer advances 8.75 miles, 8.75 / 10 = .875. So your speedometer is reading 87.5% slow.

Step 2: Find out what speedo gear you need.
Remove the speedometer driven gear from the transfer case. Do this by following the speedometer cable down to the transfer case. There will be 1 bolt to remove, and the gear should come out with the cable. Count the number of teeth on the gear. Multiply the number of teeth by how far off your speedo is and this will give you the gear you need.

Example: If you find that you have an 18 tooth gear and your speedometer is 87.5% off, 18 * .875 = 15.75. So you need a 16 tooth gear which is the closest to the result.

Step 3: Locate the correct gear and install it.
Try your local dealer, and if they don't have them, you may need to go to a company that specializes in obsolete parts. Pull the metal clip off the gear and the gear should come right off the cable. Install the new one and insert it back into the transfer case and you're done.

Step 4: Test it!
I tried this fix, the example numbers are what I came up with. When I drove the same 10 miles on the highway my odometer advanced 9.9 miles! I have also tested it by driving next to cars with digital speedometers and compared to my GPS unit, and it is almost dead on!

Please note that most highway markers are not perfect, but over 10 miles it should be pretty close. You can use a longer distance for more accuracy.


Speedometer Driven Gear Part Numbers Part Number # of teeth Gear Color
C0DZ-17271-A 16 teeth wine
C3DZ-17271-C 17 teeth white
C0DD-17271-B 18 teeth gold or yellow
C0DZ-17271-B 19 teeth natural color
C1DZ-17271-A 20 teeth black
C4OZ-17271-A 21 teeth red

1-800-543-4959 for gears (Green Sales)
http://greensalescompany.com/GreenSalesInventory.asp

 

[COBlu77]

I'm still betting on the speedo gear on the end of the cable, because you said the speedo needle moves when you turn the cable.

As far as which speedo gear to use. You will have to take out the original and count the teeth or look at the color. Here's another formula to help you calculate which one is right for you:
Old tire X Old Gear / New tire = New Gear (eg. 27in tire x 19=513/31 = 16.54 , so 17). I got all of this from Bronco Driver Magazine Vol 3, p39"How Fast Am I Really Going" by Chris Bradley. Here's another resource http://home.att.net/~jroal/drive.htm

 

[Mikey]

Hoping I can be lazy....what came stock in a 74 Bronco with 3.50 gears and a C4? I want to change to the correct speedo gear with 31 inch tires, all else is stock.

17 Teeth?
Thanks,
Mikey

 

[70TEXEB]

When I first got my bronco the speedometer needle would swing back and fourth 20 mph. I finally got the chance...after i opened up my transfer case and every thing looked good in there, to purchase a new speedo cable. Same old thing...i then disconected my new cable from cluster gauge, and hooked old one back up sprayed some zep45 (teflon coated penetrating oil) into the disconnected end line and worked that cable inside. Then took my new cable and hooked it up. It has worked great ever since. Just my case. Good luck.

 

[Mikey]

Unfortunately, mine no longer swings back and forth at all yet I can spin the gear with my fingers and get it to flicker (i.e., swing) up a bit. That'a why I'm zeroed in on my gear rather than the cable or speedo head.

 

[Unregistered]

Well this still might not fix yours...but i failed to mention some times mine would not pick up at all it would just sit at 0. I have the purple 16 tooth plastic gear on mine and it looked good. Thats why i never could figure it out....but the penetrating oil was the answer on mine.

 

[Unregistered]

I am 70TexEB at home.

 

[Mikey]

Did you have 31" tires with 3.50 gears with a C4 on yours?