Bill,

64 f100, 3 spd manual, axle code 12 ( 3.89 gear set), tires 225/70/15

Speedometer is off 10 mph on the slow side.

Speedometer gear is green plastic, part number 17r

Do I need to go with 16r, what do you think and where is best place to get?

Is this the right fuel sending unit D7TF-9275-GA?

Also, is the fuel gauge adjustable for fine tuning full and empty on the back side of the gauge?


Thanks alot,

Jayson

 

I would suggest you verify that it's 3:89. I don't know the history of your truck. But there's always a possibility a previous owner had changed gears.

 

How do I confirm the gear set.

 

Install a 16T gear, which will correct the speedometer by 7-10 MPH.

Since you know how far off the speedometer is off, and what tooth count the present gear is...why does the rear axle ratio have anything to do with it?

It has nothing to do with it...at all. Who cares what the rear axle ratio is!

If the ratio was 4.11-1; 3.00-1 or whatever...and 7-10 MPH off, the same scenario applies.

Each plastic speedometer gear (16-17-18-19-20-21 teeth) is calibrated between 7-10 MPH. The speedo is reading slow, so deduct a tooth.

CODZ17271A .. 16T Speedo Gear / Available from Ford.

MSRP: $3.04 // FTE sponsor Y2KFORDPARTS.COM price: $2.18.
-------------------------------------------------------------
D7TZ9275G .. Fuel Sending Unit (Marked with the ID number of: D7TF-9275-GA) replaced C1TZ9275K and fits all 1961/77 F Series Trucks with the in-cab fuel tank.

This sending unit is obsolete, there's only a few still remaining at dealers, obsolete parts vendors.

The gauge is off...have you checked the float?

The float is made from two pieces of copper soldered together. Solder breaks down, gas seeps in...float slowly settles to the bottom of the tank.

Shake that puppy...if you hear gas sloshing around, it's time for a new float.

The same float fits ALL 1957/79 cars/trucks/Bronco's/Econolines and is still available from Ford.

COAZ9202B .. Fuel Sending Unit Float

MSRP: $7.41 // Y2KFORDPARTS.COM price: $5.34.
------------------------------------------------
hiball3985 FYI: Members of FTE's SoCal Chapter spent Sunday blasting away at Angelus Shooting Range...in Little Tujunga Canyon.

This was our second shooting GTG, the first was at Burro Canyon off Hiway 39.

 

In his other post he inquired about changing rear gears ratio's. If the speedo is running slow theres a possibility the rear end gears may have been changed. Just changing the the speedo gear to correct the speedo isn't going to do anything to tell him what gears he has or needs.

I wasn't aware of the Little Tujunga outing... Been to busy in the garage lately.

 

Installed 16T speedometer gear and test drive showed I jumped 22mph on gauge. I started 10 mph to slow and now I am 12 mph to fast. I will test with a different car tonight. Any ideas?

Thanks,

Jayson

 

Since the speedo went from reading too slow...to reading too fast, by deducting one tooth, it's not the gear or speedometer that's causing the problem, it's the tires.

Parts catalog sez: 1964 F100 3 speed manual, 3.89-1 rear axle ratio came with the 16T speedometer gear, and...

With either 6.70-15 or 7.10-15 bias ply tires.

The problem lies with your P-Metric radials.

This is an old story, because these tires were not available until the 1980's, and are not even close in size to the original bias ply tires your truck came with originally.

Ppl that have these P-Metric radials on their older vehicles have to live with the speedometer being off...as there's no way to fix it to read correctly.

 

Thanks Bill,

I am going to have to get new rims and tires anyhow. What tire size in todays numbers will get my speedometer correct. Now I am able to use 16T or 17T speedometer gear since I have both. I did like the look of the 225/70/15 but can certainly live without it. I would like to get close to that look though.

 

These are roughly the same diameter tires, but the width varies

6.70-15 P205/75R15, 215/70R15, 235/60R15

7.10-15 P215/75R15, 225/70R15, 235/65R15, 245/60R15, 265/50R15

http://www.mopar1.us/tireconversion.html

I believe you're current tires should be close to same height as 7.10's but nothing is exact except the exact same size, another 7.10-15

 

I think I you guys discovered my problem. I measured the height of my cragar s/s with the P225/70/15 and the total ride height is 26.5 ". Shouldn't I be closer to 27.5 to 28 inches in height?

You guys are quite a resource

Thanks alot

Jayson