4.10 vs 4.56

Itchy feet · 08-09-2020, 04:58 PM

I have a 1999 ford e350 5.4 with a 4r100. she has 3.55 gears in it and sitting on 30.5" tires. I will be swapping a danna 60 front and putting on 35' tires. The way she rides now she is at 1805rpms in o/d. With the swap and 4.10s she will ride at 1816 rpms in o/d. that would keep it close to stock and and 1800 seems to be the sweet spot for mpg. with 4.56 that brings the rpms up to 2020. To me the 4.10s seem to be the best choice as that keeps it close to factory and in the sweet spot for mpg. But the guys at u joint seem to always use 4.56 gears do they know something I don't? will i be under powered with the 4.10s? Really hoping that some people with one of those setups could way in.

Chinook · 08-09-2020, 05:04 PM

I have 4:10's in my rig and little P245/75-16 tires, there are times i wish i had 4:56 in it.

carringb · 08-09-2020, 05:07 PM

Will you be towing?

Itchy feet · 08-09-2020, 05:08 PM

Quote:

Originally Posted by Chinook

I have 4:10's in my rig and little P245/75-16 tires, there are times i wish i had 4:56 in it.

like when?

Itchy feet · 08-09-2020, 05:10 PM

locally with in the state of Maine. my boat like 3500 ponds or something

Chinook · 08-09-2020, 05:28 PM

Like always, my rig weighs 10,400 pounds dry. It accelerates like a turtle fighting an 80 mph headwind. It was terrible when i went threw the Rocky mountains on my way to California. It was equally terrible pulling a trailer back home from Texas.

Twoxentrix · 08-09-2020, 06:05 PM

Gas engines normally provide peek HP & Torque at higher RPM's (I suspect that would be in the neighborhood of 3,300+ for the 5.4) - by running larger tires without reducing the gearing will be like trying to pedal your bike in a higher gear when it would be so much less strenuous for you in a lower gear - this becomes very evident when going up hill! AND, if you don't gear down, you'll just be pushing your gas pedal down father to maintain the same speed...better gas mileage shouldn't be you're first concern.
I would go the 4:56. Running 2,100 RPM's is nothing for that engine.

arctictraveller · 08-09-2020, 07:33 PM

It really depends on your usage. I've got the 5.4 with 33in tires, but don't tow. I went to 410's and as you say, that brought it back pretty much to stock, since now my speedo is accurate to within 1mph or so. I drive pretty easy, but in the mountains I find that on the steeper hills I need to down shift unless I hit them hard and keep the RPM's way up, which doesn't seem to affect the engine at all. Unless you drive a lot at high elevations, pull a lot of hills or tow a bunch, 410's could be a good compromise. If you dislike downshifting, or want more power, going even deeper with the gears will certainly help at the cost of higher RPM 's on the flats.

By the way, you could buy my already rebuilt D60 with 410's and save some money in the process. https://www.sportsmobileforum.com/fo...oat-26330.html

Itchy feet · 08-09-2020, 07:38 PM

Quote:

Originally Posted by Chinook

Like always, my rig weighs 10,400 pounds dry. It accelerates like a turtle fighting an 80 mph headwind. It was terrible when i went threw the Rocky mountains on my way to California. It was equally terrible pulling a trailer back home from Texas.

Haha nice. Ya that is a lot of weight I haven taken that in to consideration. I think I would be at least 1000 lighter not sure though maybe not

Itchy feet · 08-09-2020, 08:21 PM

Quote:

Originally Posted by Twoxentrix

Gas engines normally provide peek HP & Torque at higher RPM's (I suspect that would be in the neighborhood of 3,300+ for the 5.4) - by running larger tires without reducing the gearing will be like trying to pedal your bike in a higher gear when it would be so much less strenuous for you in a lower gear - this becomes very evident when going up hill! AND, if you don't gear down, you'll just be pushing your gas pedal down father to maintain the same speed...better gas mileage shouldn't be you're first concern.
I would go the 4:56. Running 2,100 RPM's is nothing for that engine.

from what i found as it relates to peak torque (i may be wrong) That unless your caring a large load than your just wasting energy even though your engine is running more efferently. for those situations steep hill climb and or load up hill i figured i could just drop out of o/d than im running at about 2600 closer to peak torque which is 3000rpms (these calculations are made at 65mph). Im also the guys getting flipped off because im going 40mph up the grade. im more concerned about a lack of power in a low and slow 4x4 situation