Need advice about switching rear axle

[WrickM]

ok i have never done suspension or axle work so feel to talk to me as though i am a small child of notably dubious intelligence.

My truck is my daily driver for a 43 mile commute. I run on WVO and that has been great. I saved more than the value of the truck 3 times over!

now i want to stretch my mileage out a bit and help the engine make cruising speeds , and to that end i want to put a lower gear ratio rear in. Right now it's a 3.55. So what's involved in this kinda swap and of course does anyone have a lower ratio rear that they have swapped out that they don't want.

I know the low threes aren't great for towing but my truck just hauls trash and whatever fits in the rear so i should be fine.

So let me have it. .
the speedometer sensor is in the front so i think that won't matter.
is this even a simple part-swapper like me can do?
pointers

I appreciate any advice/help

 

[gonecrazyi]

I dont believe ford offered anything but 3.55 and 4.10's for gears. You would have to swap to another set of gears such as 3.08's.

If you personally know someone who does this kind of work for a living you might be able to have the gears swapped in for cheap.

 

[pybyr]

I've never changed a ring and pinion (the gears that set the ratio) but my basic sense is that while it's not rocket science or brain surgery, it IS something that takes some proper/special equipment and some combination of substantial amounts of skill, time, and patience.

Here's a recent article that gives the flavor-
http://dieselpower.automotive.com/118505/0910dp-dana-50-front-differential-buildup/index.html

I suspect that you're going to have a hard time finding a ratio much lower than a 3.55 for the beefy rear axle types that are the likely ones to be found in your F250- but don't let me discourage you- check around, such as at http://www.ringpinion.com

 

[jperecko]

the above link to Randy's is good... 3.08s will likely be what you want.

Check out this page to compare RPMs and MPH with your old and potential new setups
http://www.grimmjeeper.com/gears.html

As you are aware of, you will lose lower end power off the line... think of it as starting in second.

The other option would be an overdrive either in the form of a new tranny or an aux. unit... that way you could maintain your off the line power.

You seem to be in the right direction

 

[SparkandFire]

I agree, I would look at your other options before dropping down to 3.08's.

The position I am in is similar, except a little more extreme. I have the 4.11's and I have absolutely no highway economy because of it... I decided the best way to get more miles out of my dollars was to get a ZF5 to install.

This isn't as economical as swapping rear end gears, i've spent a little over $1k so far and the thing isn't even in yet, but long term this seems to be a good change, and my C6 was needing a rebuild anyway...

Just consider yourself lucky, from what I hear the Sterling 10.25 is pretty straightforward to regear/rebuild. I've got an independed rear suspension differential on my wife's explorer that is pretty shot, and you basically need laser alignment tools and a full machine shop to rebuild those things, and Ford wants almost $2500 for a rebuild!!!

 

[WrickM]

thanks to all thus far. It looks like re-gearing the rear with 3.08's is the best/most economical option. I do understand i will lose some low end but i am not convinced the difference will be to oppressive. plus, i am adding an ats turbo when the weather holds out for me on a weekend.

 

[pybyr]

thanks to all thus far. It looks like re-gearing the rear with 3.08's is the best/most economical option. I do understand i will lose some low end but i am not convinced the difference will be to oppressive. plus, i am adding an ats turbo when the weather holds out for me on a weekend.

Just as a different thought-- you've got the c6 transmission, which has no lock-up torque converter or overdrive. If you put in a ZF-5 manual- if you'd be OK with a manual for your uses/ preferences- you'd not only pick up the overdrive gearing, but also the efficiency of a drivetrain that isn't constantly experiencing torque converter slip. And you'd keep the pulling ability of your existing axle in low gear. While there are a number of parts involved, I think it's probably a more straightforward process than doing a proper set-up on a gear swap.

 

[WrickM]

Just as a different thought-- you've got the c6 transmission, which has no lock-up torque converter or overdrive. If you put in a ZF-5 manual- if you'd be OK with a manual for your uses/ preferences- you'd not only pick up the overdrive gearing, but also the efficiency of a drivetrain that isn't constantly experiencing torque converter slip. And you'd keep the pulling ability of your existing axle in low gear. While there are a number of parts involved, I think it's probably a more straightforward process than doing a proper set-up on a gear swap.

I don't mind a manual, but i really don't see how swapping a auto tranny for a manual would be more straight-forward. I mean cutting holes in the firewall, reinforcing the firewall, completely removing the current trans. Changing gear can't take that long.

 

[hesutton]

IIRC Barney (flatlander) swapped 3.08's in his truck to 3.73's. Might want to PM him for driving impressions, good/bad of the swap.

Here is an old post about the 3.08's.

Heath

 

[WrickM]

thanks for the info. Seems that guy had more goin on then just 3.08's raising trans temps. Good info though. I will definitly send flatlander a message. . . .

 

[crashnzuk]

FYI, 1st gen Dodge Cummins pick-ups had 3.07s in the rear before they started using overdrive transmissions. I wouldn't think it'd be a bad thing as long as you don't work your truck hard.
Travis..

 

[Agnem]

Guess where Barney's 3.08 went? Yup... under the Moosestang, just this week. See my post I'm about to make for details.

 

[WrickM]

ok i have decided to push forward with this idea. The first step is finding the appropriate part for my truck.I was looking on ebay and it became clear i don't know which set of gears to get. Is what's in my truck the Ford 8.8? I will get under the truck and count the bolts on the cover plate soon, but does anyone just know off-hand what set i should get?

 

[Agnem]

My money says you have a Ford/Sterling 10.25 currently.

 

[RLDSL]

FYI, 1st gen Dodge Cummins pick-ups had 3.07s in the rear before they started using overdrive transmissions. I wouldn't think it'd be a bad thing as long as you don't work your truck hard.
Travis..

Apples to oranges, The cummins is a lower rpm engine, they can handle being lugged down further than our engines can. the cummins need that kind of gearing, if you put a 4:10 behind one you could get out and walk alongside