4.10's or 4.56's with V8?

[skyrat]

Originally Posted by Shaggy

Any updates on this thread? I'm considering 4.56 on 14 350 eb 5.4 v8 W/33

I have a 5.4L v8.
I did a conversion with Agile Off-Road.
Started with a stock 3.73 LS and stock rubber.
Ramsey suggested the 4.10 with the BFG All-Terrain T/A KO2 LT285/75R16 I had already chosen. They are just under 33" at 32.8". Same shift points as stock. LOVE IT after two years of mostly highway, but over 1000 miles off road. IMHO 4.56 is pretty low unless you want a primarily off road vehicle. I still pull all the grades (I go over the Conway summit from Bridegport, CA at 65 in cruise control) with plenty of power. Soooo glad I did the 4.10.

[Shaggy]

skyrat its pretty hard to argue with anything that Ramsey ever said..... You ever pull anything heavy with it?

[skyrat]

Originally Posted by Shaggy

skyrat its pretty hard to argue with anything that Ramsey ever said..... You ever pull anything heavy with it?

No I have not. If I had to tow a bunch I might go a different way. If I had heavy towing regularly I would go for a v10 or diesel if my wife could stand the smell.

[Jsweezy]

I have a v8 now and am planning on going with 4.30s. Main reason is because newer F250s come with 4.30s stock so thats gonna save me money by not having to have the axles regeared.

But also because if I go with 33s it will be killer for towing and if I decide to make a jump to 35s later it won't be an issue.

[martinli]

Originally Posted by campervanbeethoven

Update...Went w/ the 4.56s.--- Picked up the van on tues. and just got back from a short trip to Glenwood Springs. Here are my first impressions.

The van is much better on the hills for sure. Going up to the Eisenhower tunnel from Denver we pulled the whole grade, without issue, at the posted speed limit. Vail pass was still a little steep for the 5.4, but we kept up with traffic for the most part. On the interstate I've lost the ability to cruise at 75 comfortably, although short bursts up to 75 and higher are doable, 60-65 seems to be where the van likes to cruise now in OD. Around town and on the "B" roads is where the new ratio really shines. Good passing and merging power and a whole lot snapier off the line. Haven't had the van off road yet but I did drive a little in low range and this thing really creeps along nicely. Can't wait to tackle some jeep trails around the neighborhood this weekend.
All in all I'm glad I went with the 4.56s over the 4.10s, although, I think the the 4.56s are probably better suited for a 35" tire. If your running 33" tires and can put up with the lack of high speed interstate cruising and are thinking of going to 35" tires in the future, then go w/ the 4.56s. If your happy w/ your 33s, then go with 4.10s.

On a side note, when they got the rear diff apart they found the remnances of a ford lsd in there. It was not working and the clutches were eating into the carrier. They fixed it all up and now Ive got both rear tires getting power. Ye haw!

Thanks again for the input...Luke

You say "On the interstate I've lost the ability to cruise at 75".
I assume engine RPMs got too high and it gets to noisy. Or is it something else that you mean? What RPMs do you get going 75?


Cheers Martin

[E-350]

Posting my rpms with 35s and 4.56 for the sake of completeness.
Curious to see the comparison to 33s

[martinli]

@E350 yes I already saw your posting and your figures.
Using the calculator from here : Gear Ratio Calculator
You should have 77 mph -> 2387 RPM
and with 33" tires it should be 77 mph -> 2515 RPM.