What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

How much "Power" do gears give?

OffRoad

OffRoad

1/2 ton status
Joined
Dec 8, 2002
Posts
851
Reaction score
0
Location
New Brunswick, Canada
i wondering about this today. guys always talk about getting their "power" when they switch gears. i understand what they mean i just don't quite know how to measure.

for example;

you have your average 3/4 ton truck with a 350/400 and 3.73s (i realize some came with 4.10s stock, let's pretend this one didn't) running 35s. then you swap in 4.10s or 4.56s, they always say "the power came back, it's a lot nicer to drive now"

my truck has a 4.3, sm465, 3.08s and 29s. this truck is a good truck but it's kinda gutless. how much more power would i get if swapped in 4.56 gears and an overdrive transmission, say a t56 with 0.70 and 0.50 overdrive?

would it seem to have more power? i'd lose the granny low but gain a higher cruising speed with less RPMs. i only drive about 65mph on the highway now.
 
Gears make a huge difference especially if you're only adding gears and not bigger tires as well. If bigger tires are added as well that will take away from the gearing so more gearing would be required.
 
I went from 3.08s on 33s to 3.73s on 33. I can notice a difference in the mud i find this may be the perfect gear, For towing and other uses of that nature id like to have 4.10s,

When you do it you will notice a difference. If i rember correctly 2and 3 are about 1.0 away (gear wise) on the 465, now stomp it in 2nd and stomp it in 3rd the difference is noticable.

Now just keep the 465 and picture that diffence but all the time. of course its probally not goin to be that big of a difference as i described but it was an example.
 
playing with a crawl calculator, lower axle gears wont do much for your crawl ratio. now when you punch it, or are in higher gears in your tranny you will notice the difference.

if you want your crawl ratio to bump up, the best bet is your transfercase gears, or a crawler box.

best thing though is just go online, find a gear ratio calculator and play around.
 
OffRoad said:
i wondering about this today. guys always talk about getting their "power" when they switch gears. i understand what they mean i just don't quite know how to measure.

for example;

you have your average 3/4 ton truck with a 350/400 and 3.73s (i realize some came with 4.10s stock, let's pretend this one didn't) running 35s. then you swap in 4.10s or 4.56s, they always say "the power came back, it's a lot nicer to drive now"

my truck has a 4.3, sm465, 3.08s and 29s. this truck is a good truck but it's kinda gutless. how much more power would i get if swapped in 4.56 gears and an overdrive transmission, say a t56 with 0.70 and 0.50 overdrive?

would it seem to have more power? i'd lose the granny low but gain a higher cruising speed with less RPMs. i only drive about 65mph on the highway now.
Click to expand...


It sounds like what you're talking about is torque multiplication.....

Crawl ratio calculators don't tell the whole story. What you are asking seems more like "How much torque will be applied to the tires off the line?"

The calculation requires that you know how much power your engine produces at a given RPM, and that number is applied through your driveline (tranny, xfer case, axle gears) and increases due to the mechanical advantage of those gears.

The formula comes from the AutoMath Handbook:

Drive Wheel Torque = Flywheel Torque x 1st Gear x Final Drive x 0.85


In that formula the 0.85 is a correction factor for driveline losses of 15%. In a K5 it's likely to be quite a bit higher.

The next formula helps show the effect of that torque applied to the specific tire size:

Wheel Thrust = Drive Wheel Torque / Rolling Radius (in feet)

I think if you throw some numbers into Excel and play around with different axle gear ratios, it will become clear in a hurry why a truck with deeper gears "feels" like it got more power. The drive wheel torque has been increased, which helps the truck get moving more quickly....and of course, once it's rolling the engine is able to rev more quickly and get into it's powerband sooner....


:thinking:
 
Well you have a V6 so you shouldn't expect a rocket ship regarless ofgears or transmissions.

I think a T-56 would be kick ass but if your truck is 4 wheel drive then I don't know how you will adapt a t-case to the back of it. But if your truck is 2wd then go for it if have got the coin.

As far as gears, I think 3.73 is a perfect street ratio.
 
Torque is what moves the vehicle and horsepower is what keeps it moving once its there. Gears are Torque Multipliers.

Say you have a direct drive from your engine to your rear-end.
Your engine has 100lb-ft torque at the crankshaft at some RPM.
you have 3.08 gears in your rearend so 100x3.08=308 lb-ft torque at the wheels. Now you change the gears to 4.11, you now have 100x4.11=411 lb-ft torque. That 103 lb-ft of torque increase is what you feel as power during accelleration.

Its no different than trying to start your 10 speed bike in 10th gear versus 1st gear. You have a lot more torque in 1st gear so its easier to move the bike than in 10th gear.

I think...:D

Hummm...no idea why, oh how I got a thumbs down on this post :dunno:
 
Lower gears(numerically higher number), do not give you any more power.
They just move the power you have into a different place in the "powerband"
 
88Silverado said:
Torque is what moves the vehicle and horsepower is what keeps it moving once its there. Gears are Torque Multipliers.

Say you have a direct drive from your engine to your rear-end.
Your engine has 100lb-ft torque at the crankshaft at some RPM.
you have 3.08 gears in your rearend so 100x3.08=308 lb-ft torque at the wheels. Now you change the gears to 4.11, you now have 100x4.11=411 lb-ft torque. That 103 lb-ft of torque increase is what you feel as power during accelleration.

Its no different than trying to start your 10 speed bike in 10th gear versus 1st gear. You have a lot more torque in 1st gear so its easier to move the bike than in 10th gear.

I think...:D

Hummm...no idea why, oh how I got a thumbs down on this post :dunno:
Click to expand...


You took the words from my mouth.

~Brian
 
Its true though... I seriously felt like I gained 100hp when I went from 3.08s to 4.10s while running my 35" tires.
 
Gearing multiplies the torque and divides the rate of rotation. So as more gear is added, torque is multipled, but power remains the same, because the increase in torque is offset by the decrease in rate of rotation. Therefore gears do not give you more power, they give you more torque. Torque is the rotational force at your wheels that moves the vehicle.
 
You must log in or register to reply here.

Latest Posts

Top Bottom