64 C10 - gets a T5 transmission

[akqj9]

Originally Posted by Lugnutz65

Longbed and shortbed should take the same size cable. I bought my new cable from NAPA speedo cable BK 615-1606 which is 87" but if you can find an 84" cable that would be best. My 87" cable is plenty long.

Inside the T5 you have a drive gear that is either blue or red. See photo.
Use THIS ONLINE CALCULATOR and use the section named SPEEDOMETER GEAR CALCULATOR to determine what driven gear you need. You will need to know what your rear tire diameter is, the rear axle ratio (diff gear), and the number of drive gear teeth in your T5. Blue has 7 teeth and red has 9 teeth.

Driven gears are available new from vendors (HERE IS ONE) but are only available in 18 teeth through 22 teeth. If the online calculator shows you need a driven gear that's no available, please post your info and maybe there is another solution, such as a speedo ratio reducer. (see picture)

How do I find the rear axle ratio (diff gear)? Did all 1964 C10 with 235 motor and 3 on the tree have the same ratio? Can I find out by propping the rear wheels and counting the driveshaft revolutions and tire revolutions?

How do I get the drive gear out of the T5 to check?

There is a radar speed trailer near me that tells your speed on a display. When it says I'm doing 30, my speedo says 40. The spread is higher with higher speeds, like 35 actual speed vs 58 on my speedo.
I was hoping to use these numbers to calculate the percentage change I need and get the correct gears.

[jtrichard]

As long as you do NOT have a posi BLOCK front wheel jack up one rear wheel put trans in neutral turn wheel ONE full turn count the revolutions on the drive shaft and divide number of revolutions by 2 and you have the ratio

[Lugnutz65]

Originally Posted by akqj9

How do I find the rear axle ratio (diff gear)? Did all 1964 C10 with 235 motor and 3 on the tree have the same ratio? Can I find out by propping the rear wheels and counting the driveshaft revolutions and tire revolutions?

How do I get the drive gear out of the T5 to check?

There is a radar speed trailer near me that tells your speed on a display. When it says I'm doing 30, my speedo says 40. The spread is higher with higher speeds, like 35 actual speed vs 58 on my speedo.
I was hoping to use these numbers to calculate the percentage change I need and get the correct gears.

You can find the rear diff gear 3 different ways.
1. Remove the rear cover and count the teeth on the ring and pinion. Example 41 ring teeth divided by 11 pinion teeth = 3.73 rear diff.

2. Mark one rear tire at the 6 o'clock position. Roll the truck on the ground in neutral and count the shaft revolutions. Try getting 10 tire revolutions for best accuracy.

3. Put a floor jack under the rear diff so BOTH wheels are off the ground. Mark tire and count shaft revs for 10 turns of the tire. It's been a while since I did this but IIRC, the shaft turns twice as fast (or is it the tire???? Hmmmm???). Anyway, divide by 2 and do the division.

You can remove the driven gear housing in the T5 tail and look inside to see if you have a BLUE 7 tooth or RED 9 tooth DRIVE GEAR. Also, count the DRIVEN GEAR teeth (could be 18, 19, 20, 21, 22).

The speeds you give don't match well enough to figure things out. Doing 30 and seeing 40 on the speedo is a 33% error (30 X 1.33 = 39.9). That 1.33 adjustment should not change, no matter what the speed. So 35 and 58 don't go together. But 45 and 58 would be pretty close to the 1.33 correction.

[akqj9]

Now that I have the new T5, I am ready to install backup lights which did not come on my 64 fleetside. How do I hook up the wires?
Also, I will need a tool to cut a 2 3/8 hole on the bed for the lights. I have seen the hole saws with a drill in the center, but not ones to cut sheet metal.
I was told there is a hole cutter that has dies on either side of the metal that a center piece is tightened and it cuts the hole.
What is the best way to cut the hole?

[Lugnutz65]

Originally Posted by akqj9

Now that I have the new T5, I am ready to install backup lights which did not come on my 64 fleetside. How do I hook up the wires?
Also, I will need a tool to cut a 2 3/8 hole on the bed for the lights. I have seen the hole saws with a drill in the center, but not ones to cut sheet metal.
I was told there is a hole cutter that has dies on either side of the metal that a center piece is tightened and it cuts the hole.
What is the best way to cut the hole?

The reverse switch simply completes the circuit. You would just need to wire it into the reverse light circuit.

I can't comment about cutting holes in the fenders. I have no experience with that.