I know that everyone is going to think that I am a dummy for asking this , but if I were to change gears to 4:30 from my current 3:73, what would the hypothetical increase in torque and hp be? I know it probably isn't an actual increase but there has to be some kind of equivalent to an actual engine mod that produces an increase in power. No?

 

The question isn't as silly as it sounds. While the crank power doesn't change, the torque to the rear wheels does. I have no idea how to figure it, but we have some really smart guys on here that probably can.

I have no idea what to tell you on the feel like scale, as it doesn't feel like there's a ton more hp, but the torque difference is significant. This is comparing my dads 4.30 vs my truck when it was stock and both having the same wheel and tire package. I've said it before, at wide open throttle, the 4.30 trucks aren't really much faster than 3.73 trucks. The 3.73 holds the truck in the upper power band a little longer, and that's where this engine likes to live. The 4.30s just help a ton down low, great for towing.

 

Thanks I am on the fence on getting a new truck with the 6.7 or re-gearing the currant one which I don't want to part with, but our fifth wheel got larger this year and has a greater frontal area which really drags in the wind and grades. Although we haven't done any mountains with the new to us fiver yet, I am concerned about west coast mountain areas where we usually go to visit relatives in BC. We do a lot of towing about 65,000 miles in the last 4 yrs,

 

no question... change to 4:30 if going to mountains.

or the 6.7.

I have done the east coast hills.. WV and areas.. with 9,000 pound pull trailer... it does well.. but not mountain well.

I have been to the west coast mountains by car and motorcycle.. over 12,000 feet.
can the 6.2L with 3:73 do it "YES". just not easy or quick.
my opinion,
.
to your question..
horsepower produces top speed.
Torque is acceleration. gears only change torque. but lowers top speed.
think of a very rusty bolt. and use a 6 inch long wrench.. now use a 12 inch long wrench.. the 4:30 is like the 12 inch wrench.

4:30 allows more weight to be moved with less work for the engine.
.
diesel was designed to hauling... but do you need one.. only you can answer that.
if going diesel.. you still need to understand what gear is best of it.


as for a Dumb question.. is the one NOT Asked.
.

 

Somebody please correct me if I'm wrong...

Torque leaving your engine is multiplied through the tranny gears and axle gears. For simplicity let's say you are currently driving with a tranny gear that has a 1:1 ratio. So the torque leaving the tranny is 1 times that leaving the engine (there is parasitic loss but let's leave that out for simplicity). Then the power goes through the axle. A 3.73 axle gear would multiply your engines torque (430 lb ft at 3800rpms for the new 6.2) and create about 1604 lb ft of torque (again, let's leave out parasitic loss for now). A 4.30 axle would multiply your engines torque by 4.30 and give you about 1849 lb ft of torque. This would be an increase of about 15% torque applied to your rear wheels.

HP is directly related to torque so your hp would increase by 15% also.

 

it is a very complicated relationship.

added horsepower is because the engine is turning faster and the gearing is allowing the engine to spin up faster.. speaking of the 4.30

but its' not 1 to 1...

I am not an engineer.. just an old racer and mechanic.

just like going smaller in tire diameter... Leverage of each part to each other.

 

That's pretty much the trade off. You gain leverage on the tires but have to either accept driving a little slower at the same engine rpms or increasing engine rpms to maintain the same speed.

Due to the increase in mechanical advantage, the 4.30 axle gears would reduce stress on the engine and tranny. In other words, less effort is required by the engine with the 4.30 gears. Engine would spin faster but not have to apply as much torque to the tires to move your load.

 

Yes this, and the fact that the gear difference is 15%, so you have a 15% leverage advantage with 4.30's. That 15% is definitely noticeable. I really disliked towing with 3.73's. My current 4.30's make towing tolerable for me.

 

There is also an increase in parasitic drain on the power plant. So it's not truly a straight 15% increase. There is more driveline drag on the steeper gear set also.

I have 3.73's in my truck, and I make no bones about being a big proponent of that gear set. I think it is much maligned and impuned across the interwebs and FTE as well.

That being said, I have always thought that if a guy is pulling heavy ALL THE TIME, or most of the time, AND/OR pulling in mountains all the time, that 4.30 gears are mandatory for the gas 6.2 . I've also thought that in this demand, the 6.7 diesel would be a better option.

Now most guys don't really have that actual application demand, and for a general purpose truck, the 6.2 + 3.73 combo is a great setup, interwebs-be-damned.

But for the OP's SPECIFIC case, I would recommend at least going 4.30 gears, if not a straight trade out for a 6.7 diesel truck.

 

I never follow ...
and the internet ( folks ) are mostly uninformed.. but offer bad (Poor) advice.

towing heavy 50 percent of the time or mountains often... 4.30
the 6.2L and 3:73 is very capable.

my total rig weight is 17,000 pounds. ( cat scaled )...my truck has 152,000 miles.
April 2017 .. trip,, 1,800 miles in 4 days... south Texas to N.E. Ohio not one issue.
I departed Texas at 101 degrees and arrived in Ohio in 33 degrees... and 6 inches of snow.

 

only real reason for a Diesel is the Turbo...

I did some walking at 12,000 feet... it is very hard to walk 1/4 mile that high...
so if you want to tow over 8,000 feet many times... a turbo....

 

I hate turning this into yet another thread on 4.30 vs 3.73 debate, but I just don't understand how someone that has never driven a 4.30 truck can come up with this.

Take it from someone that has substantial seat time in a 245/75r17 3.73 truck, a 245/75r17 4.30 truck(my dads) and a 4.88 37x12.50(close to a 245/75r17 4.30 gearing) truck, that the lower gearing is all around better.

It's better for someone that does a lot of in town driving, it's better for someone that tows even light, and it's better on the highway if you have larger tires, even the factory size larger tires. The one and only place that 3.73's win is a small factory tire truck running empty down the interstate.

It's a 7k lbs truck with a double overdrive transmission and a gas motor that likes to rev. You don't take a beating on fuel mileage with 4.30's, infact, you may see an improvement, so why would you not want the lower gear set?

If you throw towing, mileage and everything else out the window, the 4.30 just makes for a better overall driving experience in these trucks. Even if you have the smallest tire offered, if your towing at a responsible 65 mph, you still haven't broken 2k rpm. You barely break it at 70. The motor is not screaming. Is it screaming when you drop to your 1st OD, 5th, on every little grade with 3.73's? Because you are then turning more rpms than a 4.30 truck in 6th.

It's not a bunch of people feeding others with BS on the internet. It's people giving good advise. Especially some of us here on FTE that have driven, and even owned both.

Maybe a 6.7 would be the OPs better option, especially with the miles he has racked up towing. But since he didn't give us the specs on the trailer, just that it has more frontal area, we can't say.

 

personal choice.

I have (not in a truck) 5.13's with 15 inch wheels..
I have also run a car with 4.56 and 15 inch wheels..

but it does not bother me to have a V8 cruising at 3,500 rpm,s or even 4,000
but I have raced motorcycles 1,000cc 4 cylinders at 12,000 rpm's

personal choice.

 

Wasn't directed toward you chuck, you just posted while I was typing.

The vehicles you are talking about don't have a final overdrive of .67.

 

I still VOTE for a 2 speed rear end ... was made by Eaton.....
I think 5 to 10 ton.

like the ones in a White
towing real heavy

1 low, 1 high, 2 low, 2 high, 3 low, 3 high, 4 low, 4 high, 5 low, 5 high.

OR just low or high..