Hi people,
I am new to the "New" Ford Truck list, but was a member
of the "old" list back in 1997(?). Since then I have had a
heart attack, am recovering, AND have changed the rear end
gears in my '79 F-150 (2wd). Went from a 2L75 to a 3L25 and
my annual mpg, which usually runs in the 20.2 to 20.8 range,
was 19.8 mpg for the year 2000 with the 3.25s - I'm happy!
(But I have to keep a calculator in the truck to figure out
my speed and distance traveled because I can't find the
correct speedo driven gear.)

I ordered this truck from the factory back in Oct. of
'78. Even though I ordered it with the 3.25 gears and
Traction-Lok, Ford, in their wisdom, shipped it with a 2.75
Traction-Lok, in order to help them meet their CAFE (Gov't
mandated C-orporate A-verage F-uel E-conomy standard.)

So the 4-speed manual overdrive tranny came with a 16
tooth driven speedometer gear, with a LEFT HAND pitch. With
the 3.25s and tires I have on it, I need a 19 tooth speedo
gear. I have been to a number of FORD dealers (they hate to
see me coming) and they always try to give me a gear with a
RIGHT HAND pitch. As a matter of fact, the first 19 tooth
gear they sold me, I didn't realize there were left hand and
right hand pitch gears, and I installed it (it went in the
tranny okay) and with in 100 feet I noticed that the speedo
was kinda herky-jerky. Stopped and pulled the gear out and
it was all chewed up. Compared it to the original and, duh!
One was right hand and the original was left hand pitch.


Ford dealer says that the ONLY gear made for this trany
was a 16 tooth LEFT hand pitch. I am under the impression
that this tranny was available in Ford Granada's, Mercury
Monarch's, F100s, F150s, Bronco's and Vans. Were they all 16
tooth? Can any one confirm? Does any one know of any other
applications? Anyone know of a 19 tooth left hand pitch
gear?

I hear those Ford manual pages fanning the air.......TIA

 

We had a 77 Granada with a 302 that had this transmission and I still have an 85 F150 4x4 351W 2v with that trans. I've have put bigger tires on it and have changed the gear to correct the speedo but can't remmember which pitch it was.

 

Thanks for the info, Mr. redstone
Do you still have the old speedo gear that you replaced?

(Right hand pitch gear)
////
////
////

(Left hand pitch gear)
\\\\
\\\\
\\\\

And where did you find the new speedo gear?

 

I do still have the speedo gear that I took out and will have time to look for it this afternoon. The gear I took out was black and the replacement gear was pink/beige. I'll look for it and e-mail you back.

I bought it at the Ford dealer, they just wanted to know how many teeth the old gear had and how many teeth I wanted the new one to have. IIRC 5% change ment one tooth. But it was about 5 years ago.

 

I currently have a 16 tooth left hand pitch speedo gear that came from the factory with the original 2.75 rear gear.

I am looking for a 19 tooth left hand pitch gear to go with my current tires and 3.25 rear gears.

 

[font size="1" color="#FF0000"]LAST EDITED ON 12-Feb-01 AT 07:23 PM (EST)[/font][p][font size="3" color="#191979"]

I used a pink 19 tooth speedo gear on my F100 to correct the speedometer, C0DD-17271-C is the part number. It mated with a blue 9 tooth drive gear, D7TZ-17285A. That truck has a 2.75 with approx 27" tires. I ended up changing later to a white 18 tooth gear C0DD-17271-B to correct the speedometer for the 28.5" tires.

I have pulled the OEM speedo gears out of a 1969 F100 (scrapped the truck) that had 3.25 gears, and the original combination was a 7 tooth drive gear C3OZ-17285-C driving a 16 tooth driven gear C0DD-17271-A. This was for stock tire size and may need to be adjusted up/down if you have bigger/smaller tires.

Here's a cool site to check speedo gear ratios, as most speedomoters have a SAE standard shaft speed at 60MPH:

http://www.tciauto.com/tech_info/speedo_gears.htm

I will have to check my parts stash to see if the driven gears referenced above are right-hand or left-hand helix. Will advise later,

Art

 

I found my old gear, it is a BLACK, 20 tooth, right hand pitch (according to your previous post).

Did you have a shop change out the gears in the differentials or did you do it yourself. If you had someone do it, how much did it cost if I may ask. I am considering going to 3L73 or 4L11 on both ends. Right now I've got 3L50's in in both cases from the factory. I've got 31x10.5x15's on.

 

One more thing I forgot to put in the last message, when I went from the stock P235's to the 31's, (27.5 inches to 30.5 inches). I needed to change about 5 percent to correct the speedometer, so the Ford dealer gave me a 19 tooth gear (beige or pink) but I'm sure it was a right hand twist since the one I took out was.

 

>I found my old gear, it
>is a BLACK, 20 tooth,
>right hand pitch (according to
>your previous post).

redstone, was this right hand pitch gear out of a "RUG" 4-speed OD 2-wheel drive tranny? (Ford dealer is telling me that my "RUG" 4-speed OD tranny is the ONLY one that uses the LEFT hand pitch driven gears? ? ?)

>
>Did you have a shop change
>out the gears in the
>differentials or did you do
>it yourself.

After looking for a year +, my son in Ohio found someone out there selling a complete 3L25 rear end (except brake drums), thought to be out of a '78 F-150. It had the 31-spline diff that I needed, so he made the purchase and I hauled it back to Upstate NY on my next visit to Ohio.

I pulled the pumpkin out, dismantled it, checked all the gears and bearings. Traction-Loc seemed okay. I did install a pinion seal. It took me about 3-days to re-set the used gears up, and I did have to buy a shim pack to get the pinion depth, backlash, and pattern where I was satisfied with it. Then I just swapped pumpkins, pulling out the 2.75 and putting in the 3.25. I say "just" swapped, but be aware that the pumpkin weighs 72 lbs!

Got about 4000 miles on the 3.25s, including a couple of 300 mile trips, one 600 mile round trip pulling a boat, and it seems fine. Adjusting the mileage for the speedo error, I GAINED about 1/2 MPG around town, and lost about 1/2 MPG on the Interstates.

Just as as aside, I think the 3.25s are near perfect for the 55 MPH speed limit roads, A 3.00 would be about perfect for 65 MPH Interstates, and the original 2.75s are about right for those states that allow 75 MPH on their Interstates. (Thats with my 237-70-15s (28" tall, with 749 rev per mile on 15X7 rims.)

If you
>had someone do it, how
>much did it cost if
>I may ask.

I think we gave about $250 for the complete axle assembly, the pinion seal was about $10, and the shim pack was about $10.

>I am considering going to
>3L73 or 4L11 on both
>ends. Right now I've
>got 3L50's in in both
>cases from the factory.
>I've got 31x10.5x15's on.

 

PDQFORD,

The tranny in the 77 Granda was a 2 wheel drive unit but that car is long gone and is in a junkyard in Denver somewhere.

The 4 Spd Manual OD in my truck is on a 4x4 and I think the tranny is officially called a TOD by Ford. Top loader OverDrive? Not very many of them around. In fact I have never seen another. I special ordered this truck in 1984.

Thanks for the info on the installation. I just changed out the original fluid in both differentials to synthetic last week.

 

[font size="3" color="#191979"]

Sorry about the part numbers I listed, they are not what you need. They're all right-hand helix (driven) gears - for T-18's, NP435's, C-6's, etc...

Art

 

Right now in OD at 55 mph the tach is showing 1600rpm, that's with 3.55 rear axle gears, a 0.71 OD in the tranny and 31, 10.5x15 tires.

Hence my wanting to go to 3.73 or 4.11's to bring the rpm up. 2000 rpm is 67 mph on this truck

 

REDSTONE,
You got the BIG tires! My 235-70X15s and 3.25s give me about 2100 RPM @ 65 MPH.

 

 

I know this is old, but I like to see accurate info. The direction of the teeth on the driver speedo gear is determined by how the gear fits into the transmission. If it is on thew drivers side, you use a gear with the teeth going back to the left. If it is from the passenger side, then teeth to the right. There certainly are many gears with the teeth going back to the left, those dealer parts guys were incorrect.