Hi All,
Speedometer stopped working and after inspecting cable and driven gear all seems well, in fact it all spins freely and turns the speedometer when twisted by hand. Couldn't figure out what was wrong and thought the cable end was slipping out of either speedo, driven gear, or both. Turns out what seems to be happening is that the gear inside the transmission is wore out and isn't driving the gear on the end of the speedo cable anymore. I could feel it inside and then got a few pics...(see below)

Here is what I need help with:

• Is the driven gear inside the transmission available anywhere? Does anyone know where I can find it?
• How would I go about replacing if it was available? can it be done by removing the tailshaft or do I need to pull the transmission?

Truck is a 1976 F250 Camper Special, 390, 2WD, original 3.73 rear end, NP435, and came originally with 9.50 x 16.5 tires.

Thanks for any help anyone can provide

 

Speedometer DRIVE gear located on the output shaft of the transmission // Speedometer DRIVEN gear located at the end of the speedo cable where it fits into the trans.

1975/76 F250 2WD NP435 3.73 Dana 60 with 7.50R x 16 & 8.75 x 16.5 & 9.50 x 16.5 tires.

CODD-17271-B .. 18T Nylon Speedometer DRIVEN Gear / Available from Ford and auto parts stores.
-----------------------------------------------------------------------------------------------------------------
C3OZ-17285-C .. 7T Steel Speedometer DRIVE Gear / Obsolete

NOS PARTS SOURCE in Olathe KS has 1 = 913-220-5746.

MUSTANG'S ETC in Van Nuys CA has 2 = 818-787-7634.

TISCHNER FORD SALES in Santaquin UT has 2 = 801-754-3281.

 

Thank you ND, I meant to type that it was the drive gear on the transmission shaft....sorry about that
Your reference to part #C3OZ-17285-C .. 7T Steel Speedometer DRIVE Gear / Obsolete is interesting to me as the part in the transmission is almost certainly plastic. A steel part would make a lot of sense as it is much easier to change the speedo cable and/or driven gear than the drive gear I would think.
The mustangs etc. part shows online as plastic and the part number refers to steel (also shows as steel on google search)
Are these the same part or will either work? Is there a preference...I am sure steel will never need to be replaced.

I would love to know if this can be replaced without taking the transmission out...

 

I've seen both steel and plastic drive gears inside the transmissions and transfer cases over the years. Never paid enough attention though, to remember where I saw each type.

Never seen the steel ones available new before this, but have seen plastic ones advertised over the years. Not sure what applications though, so maybe those were not NP435 types.
They probably sell the plastic ones because they're so prone to wearing down like yours. Never actually seen a steel one worn out, but we look for them due to the two different tooth counts available for the Bronco D20 case.

If someone that ND lists has a metal one in stock that's supposed to fit the NP trans, I'd grab it in a hurry and hope there were no undocumented running changes in the gear boxes!
I don't see why there would be a difference in shaft size, but I don't know enough about NP 435's to know whether or not there were variations that would cause you trouble.

Good luck.

Paul

 

Not a NP435 but a T18 2WD that I had to change the drive gear on because of the same thing as yours.
My T18 in a 81 F100 with a 300 six is a slip yoke at the transmission, drop the drive shaft, remove the tail housing, I forget how the gear comes off but I am sure you can figure it out once you see it.
It was not hard at all to do.

I used a little make a gasket RTV to seal the housing to the trans.
Also used it on the top shift tower cover as it was leaking too.

I am going to swap in a NP435 and have been told the speedo gear (driven) will work from the T18 in the NP435 so I am happy to see Bill said the same thing.
Good luck on the change out its not hard.
Dave ----

 

Thanks for the advice and confidence boost. Ordered the steel gear today, looks like it slips on with some sort of keyway or setscrew based on the pics. I ordered a gasket set today also and will try to take some pics when I am in the process. Good to know that the RTV works as well.
Stay tuned and thanks again

 

Hi All,
A quick update and a question/request for tips.
I ordered and received the steel speedo drive gear (pics for posterity) and am preparing to install it. I first need to get the tailshaft housing off and here is where I am moderately stumped. If I try to remove the bolts holding the the housing to the crossmember, labeled "1" on the pic, they don't back out far enough to release the housing...they actually hit the crossmember before they are completely screwed out of the housing base. It looks like there is a single center bolt that might hold the bracket itself to the crossmemember, labeled "2" in the pic; if I remove bolt 2 should that allow the whole thing to lift off of the crossmember? (after I remove the other 4 bolts labeld "3" of course). If that happens will it be tough to slide it off over the shaft or will it be loose but not able to go high enough to release the bracket from the crossmember before it hits the shaft?
I think I could undo the crossmember and slide it backwards with the housing on it but it will only go so far before hitting the front fuel tank...and it might not be far enough to clear the shaft...I guess I don't know how far out the shaft protrudes.

One thought was to drill a couple of holes in the cross member directly under the bolts (1) and then get a socket on them and take them all the way out?

Hoping someone has some hints or knows the "easy way" so I don't have to do it the "way too hard way" : )
Thanks in advance for any assistance.

 

Well I can't help with the logistics (looks like they made it a puzzle), but I will say wait for someone to tell you, or find the book to tell you, whether or not you can simply remove the tailshaft housing without doing something like locking the transmission into first gear or something like that in order to keep the output shaft from sliding out far enough to allow the roller bearings to fall out of their cavity between the main input and output shafts.

I do not know the 435, but the Ford Top-Loader and 3.03 3-speed have these bearings. And in this regard I believe most manual transmissions of the day were the same. Or at least similar in their design.
In other words, you don't want this gear swap to turn into a full transmission tear-down to re-insert those loose rollers!

To your question though, are you able to remove the crossmember itself?

Paul

 

Does your drive shaft slip into the transmission or has bolt that hold the Ujoint to the transmission? Either way the drive shaft needs to be removed.
Once removed if there is a yoke that is bolted to the out put shaft this will need to be removed.
On the mount remove that center bolt & nut #2. Jack up the transmission to undo the them other bolts #1 and now remove the mount.
I did not remove the cross member.
You can now remove the 4 bolts #3 holding the tail shaft housing to the main body of the transmission.
You can now see the gear you need to change out. I don't remember how it came off.
It may have just slipped off & on and there was a key that kept the gear from spinning on the out put shaft.
Dave ----

 

I knew I was probably making it too hard. Driveshaft is out and yes I will to remove the nut holding the yoke on (any special advice or crazy torque #s like a pinion nut?) I should have thought to jack up the trans. Will make an attempt later this week or this weekend. Thanks again!

 

Thanks for all the help so far, it is much appreciated for sure
Ok here is the update r.e. my speedo drive gear adventure and my new questions:

Update: Fought with the yoke retaining nut and finally got it off (1/2" impact, breaker bar, kroil, and colorful vocabulary for motivation), jacked up the trans a little and was able to remove the tail housing extension. The speedo drive gear was retained or at least centered by gods own retaining/snap rings (I had to fight with that one too since my snap ring pliers don't open quite enough). Anyway the worn out speedo drive gear slid off after removing the rearmost retaining ring, however it does not match the drive gear that I ordered. My dilemma looks to be similar to this thread https://www.ford-trucks.com/forums/7...rive-gear.html

Hoping you all can point me in the right direction in terms of parts and some insight/advice:
Questions:
1. What part number should I order or search for? Is it D3TZ-17285-A (type 12?) as indicated in the above linked thread? That one seemed to be 1974 specific and my truck is a 76 (been in the family since new and no trans change/exchange). My truck does have 3.73 gearing and same tire size mentioned in the linked post, so maybe?.
2. If I get a replacement that matches my worn out gear, how in the heck is it affixed to the shaft. There are some splines but it rides on a smooth section of shaft, BUT, there does appear to be some plastic (cast in?) piece in a hole that might work to fix the gear to the shaft via one of the splines (see pics) but it also could have broken off of the gear?
3. Anyone have a secret for those hardcore soviet style snap/retaining rings?

Thanks in advance for any help or thinking on this.

I also added some pics of the NOS steel gear I ordered in comparison to the one that came off. Maybe it will help someone down the road

Broken or good to go?

Just for posterity


May have tweaked this getting it off.

 

That little plastic piece is the drive pin for the speedometer drive gear.
Speedometer drive gear pin
D4TZ-7235-A
9/32" long X 5/16" diameter used w/ D4TZ-7003-F, G or D5TA-7003-BA NP435 transmission
As for the retaining rings, I have a pair of lock ring pliers, not snap ring pliers. Picture a pair of needle nose pliers only with a flat, blunt tip instead of a needle nose. Much more mechanical advantage than plain snap ring pliers.

 

As for being '74 specific. One thing you learn real quick when you start learning how to use the Ford parts catalog, while "generally" they're fairly accurate, don't bet you life on it .

 

received all my parts, and put everything back together over the weekend. The drive gear on the output shaft was a teeny bit long preventing the retaining clip from dropping into the groove. I put some rough sandpaper on the bench and sanded off about probably less than 1/16" and it fit fine. Had to wait an extra day for the new speedo driven gear (changed tire size from previous) and retaining clip (somehow I lost that) and stuck that in the next day. Drove it and the speedo works fine. I do want to check accuracy via my phone but haven't done that just yet. Thanks for all the help.

Ready to go, waiting on parts

New gear, new seal, gasket, and all the bits lined up...

New sharp teeth

 

Glad you got her fixed. Thanks for the update.