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 Message Boards » » TALLER final drive ratio? Page [1]  
theDuke866
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My truck ('66 Chevy C-10) is finally nearing completion. It's should be at least 100 hp stronger than original 165 hp, and maybe 120+ more.

The 3-speed column shift transmission is retained. There is no overdrive gear.

I'm not sure what the final drive ratio is, but I'm considering changing gears for a TALLER ratio. I don't think I've ever heard of anyone swapping stock for taller gears, but I'm thinking that with so much more power under the hood, I'd be much happier at highway speed and not really pay any penalty in acceleration and driveability, especially since the 3-on-the-tree doesn't make for quick shifting.

I do plan to tow some with it. Say, 3000 lbs of boat.

What do you guys think?

3/24/2017 11:41:52 PM

NeuseRvrRat
hello Mr. NSA!
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first thing to do is find out what rear end ratio you have now and what the 3rd gear ratio is on that transmission (1:1?)

but i have heard of plenty of guys doing this to reduce RPMs at highway speeds on older trucks. like you said, yeah, you'll give up some acceleration, but the increased HP should more than make up for it.

go for it

3/25/2017 10:17:07 AM

smoothcrim
Universal Magnetic!
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might be way more complicated, but what about a push button OD from something from the 80s?

[Edited on March 25, 2017 at 12:10 PM. Reason : and the accompanying transmission]

3/25/2017 12:10:03 PM

NeuseRvrRat
hello Mr. NSA!
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Seems like keeping the column shift is a priority. Ditch the column shift and you have tons of options better than that^

3/25/2017 3:28:33 PM

beatsunc
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can also make rear end ratio seem taller with larger circumference tires in rear...

3/26/2017 12:11:29 PM

theDuke866
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^^^^

Stock is 3.73 (3rd gear is 1:1). I'm thinking something in the 3.20-3.40ish range.

It's not just a matter of the increased power more than making up for it, sacrificing acceleration for highway RPMs. I think it won't ultimately hurt the acceleration, overall--1st and 2nd gears will become more usable for longer. It's not like it's a close-ratio 5 or 6 speed. Those gears are WIDELY spaced.

1/21/2018 10:55:16 PM

NeuseRvrRat
hello Mr. NSA!
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what size tires are you putting on it?

1/21/2018 11:42:04 PM

theDuke866
All American
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Not sure. Pretty moderate size. Bigger than the little donuts they fitted in ‘66, though. Let’s guess and say 235/75?

1/23/2018 12:54:28 AM

tchenku
'vast that foolery!
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Quote :
"can also make rear end ratio seem taller with larger circumference tires in rear..."


my thoughts exactly

go for this look: http://www.tnrods.com/uploads/primary/large/1431980186.JPG

1/23/2018 9:39:04 AM

underPSI
tillerman
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Instead of swapping gears why not just replace the whole axle? You can probably get one from a 88-98 1500 with 3.42 and the g80 locker for ~$500.

Personally, I'd leave the gear ratio alone.

1/24/2018 8:40:42 AM

arghx
Deucefest '04
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Does the engine have better low end torque now? That would offset the higher ratio.

1/27/2018 2:18:11 PM

theDuke866
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The engine will have more everything. The gains will probably be less pronounced in the low-end (more aggressive cam, single-plane intake, oversized valves, etc), but I expect it will gain substantially across the RPM range (much higher compression ratio, for one thing).

Stock hp is like 160 or 165...I'm guessing this thing is gonna make something in the neighborhood of 280 or more (at the crank).

That's kind of the whole point of raising the ratio. It's only a 3-speed, and first gear is short enough that I feel like it's going to pull through it REALLY quickly with 3.73 final drive. Since the column shift is not very fast, I think it might work a lot better to have a significantly taller final drive ratio, so that 1st and 2nd gears will get it pretty much up to speed while only needing 1 shift, and then 3rd (1:1) will be a better cruising gear. As a side benefit, the torque delivered to the axles will be reduced with the taller ratio, making them less likely to break (now if the transmission will hold up...we'll see.)


Yes, I understand that this is a suboptimal solution from an engineering perspective. If my priority was bulletproof quarter-mile passes, I would have done a hot V-8 and built 700R4 swap. I could have gone with polished hardwoods in the bed, a custom candy apple paint job, power-assisted disc brakes, power steering, etc...but my priority is keeping it basically like it was as a farm truck when I was growing up and learning to drive on it, except brought back to somewhat better-than-new condition, with the old straight-six considerably, umm, surgically enhanced, and with the suspension modestly beefed up (3/4-ton spec and about 1/2 to 1" lower), and a limited-slip added.

...oh, and with air conditioning, since I live in FL.

1/28/2018 3:28:57 PM

theDuke866
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Forgot to ever update this...

Went with 3.42 gears. Couldn’t do a helical limited slip, as nobody makes one that will fit a 12-bolt with the gear ratio I wanted. Did a clutch-type posi unit instead.

Hopefully should be finished soon...

10/1/2018 9:36:12 PM

beatsunc
All American
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cool, we will need pics of course

10/2/2018 8:24:20 AM

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