Did all 66 Chev c10's have 4:11 gears?

[Juspassinthru]

My truck is s 250 3 speed ad i want a better hiway gear.... Whats my best financial route? I want 3:08's
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[Captainfab]

No not all '66's had 4.10 gears. Although I have seen a couple 6cyl trucks that did. In my experience, most of the C10's had 3.73's. Your most cost effective way to get 3.07 gears is to find a complete rear differential from a '65-'72 C10 with trailing arms and coils. That is assuming your truck has trailing arms and coils.

[kieth]

Originally Posted by Juspassinthru

My truck is s 250 3 speed ad i want a better hiway gear.... Whats my best financial route? I want 3:08's
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I would be careful about changing gears without looking at the end results first. Send me a PM with your e mail address and I will send you a spreadsheet that shows usable torque to the ground with different engines, rear axles and tire sizes....here is what I need..

1. current engine, engine you are thinking of changing to....

2. transmission you have now and trans you want to run later

3. height of rear tire from ground to top of tire of the tires you have now

4. same info for tires you might change to.

I will send you a spreadsheet that shows speed, and torque for all combinations you say you need. Kieth

We have to be careful, the speed line may look great but the usable torque may make the truck unable to get out of its own way in 3rd gear....usually folks decide to change the transmission out along with the rear end to make the truck a nice highway cruiser........(low rpms)

[tincan1966]

Originally Posted by kieth

I would be careful about changing gears without looking at the end results first. Send me a PM with your e mail address and I will send you a spreadsheet that shows usable torque to the ground with different engines, rear axles and tire sizes....here is what I need..

1. current engine, engine you are thinking of changing to....

2. transmission you have now and trans you want to run later

3. height of rear tire from ground to top of tire of the tires you have now

4. same info for tires you might change to.

I will send you a spreadsheet that shows speed, and torque for all combinations you say you need. Kieth

We have to be careful, the speed line may look great but the usable torque may make the truck unable to get out of its own way in 3rd gear....usually folks decide to change the transmission out along with the rear end to make the truck a nice highway cruiser........(low rpms)

Very good advise! There's a reason why GM assembled them the way they did-to perform as intended.
A later model 5 speed trans is sometimes a better upgrade than the rear gears.

[perro13]

Originally Posted by kieth

I would be careful about changing gears without looking at the end results first. Send me a PM with your e mail address and I will send you a spreadsheet that shows usable torque to the ground with different engines, rear axles and tire sizes....here is what I need..

1. current engine, engine you are thinking of changing to....

2. transmission you have now and trans you want to run later

3. height of rear tire from ground to top of tire of the tires you have now

4. same info for tires you might change to.

I will send you a spreadsheet that shows speed, and torque for all combinations you say you need. Kieth

We have to be careful, the speed line may look great but the usable torque may make the truck unable to get out of its own way in 3rd gear....usually folks decide to change the transmission out along with the rear end to make the truck a nice highway cruiser........(low rpms)

Right on Keith. Got to love the help % wealth of knowledge, You too Cap

[Juspassinthru]

im running a stock 250, stock 3speed on column, 215 70 15 tires, I do alot of highway driving and im gettin like 13 mpg.dont really want the expense of changing a complete transmission and driveshaft.if i could get 16 or so mpg i would be happy the rear end gear seemed like the logical choice in regard to expense.

[kieth]

Originally Posted by Juspassinthru

im running a stock 250, stock 3speed on column, 215 70 15 tires, I do alot of highway driving and im gettin like 13 mpg.dont really want the expense of changing a complete transmission and driveshaft.if i could get 16 or so mpg i would be happy the rear end gear seemed like the logical choice in regard to expense.

Here is the info I came up with :

3.08 gears
24" tires ---2000rpm 46.5mph, 2500rpm 57mph, 3000rpm 70mph

28" tires 2000rpm 54mph, 2500rpm 67mph, 3000rpm 81mph

30" tires 2000rpm 58mph, 2500rpm 73mph, 3000rpm 87mph

The tire diameter can be just like a gear set change.....Your 250 will be ok, the torque does not fall off that much....Kieth but as you try to go faster on a windy day you will be able to tell that it does not have much umph but your fuel mileage should be better if you will cruise at about 65mph.

[Juspassinthru]

Thanks, 3:08 looks like the ticket
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[Juspassinthru]

Looks like 3:08 is the way to go
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[Juspassinthru]

do you have the same equation stats based on my current 4:11 rear?

[lmdangerous]

Go to Randys Ring and Pinion - there is a rpm, speed calculator.( has a online calculator program -free) You can play with the tranny options , gear ratio, tire height , and other stuff - give it a try .
LMD

[Juspassinthru]

Thx
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