thoughts and speculations on changing my gearing

Hi. as some of you guys know, im a 16 year old kid, which implies that I am (when its comes grandeur and spectacular over reaching ideas of truck "improvements") rather incompetent. this being said, if this project idea is well over my head and to large, don't be afraid to shoot it down. that aside, my idea is to change my gears in my front and read differential. im no expert on changing these and have yet to fully understand how a 4x4 drivetrain works mathmatically. I want to change my 4.56 gears to 4.10. I don't tow much and I don't need those large 4.56 gears. having the smaller gears im hoping will improve my highway speed and possibly gas milage, although it is a 460 so im definitely going to remain single digits or very low double. I need to find out what transmission and transfer case I have, but im hoping you all can help me decode a few pictures and help me out. any help at all on choosing gears, changing gears, and a hand on figuring out my situation would be very greatly appreciated.

- Jack

So from your post we know its a 4x4 with a 460 think that all we know.
What year is the truck, auto or stick transmission?
What size tires on the truck or you plan to run as this will dictate the gearing you need.
Suspension or body lift on it or planed?

A gear swap is not cheap and you have it x2.

I can tell you if you have not done a gear swap and you will need to do it 2 times it is not something for some one that has never done it before to do. I have done a few (5) over the years with help from a buddy and only now would I even try it by my self, would have to as buddy is many miles away from me now.

Do you know what rear axle you have in the truck now?
If a 9" you can get a center section already set up so you pop the axles out, drive shaft and the center section out and pop the new one back in.
Then all you need to deal with would be the front axle gears and you could send it out for that at 1/2 the cost as you are only getting 1 axle gears swapped.

Just my .02
Dave ----

Jack - Dave is right.  This won't be cheap nor easy.  And there may be less expensive alternatives.

But first, we need to know a lot more about your truck.  Please tell us if it is an F150, 250, etc.  What transmission.  What size tires?  Etc.

As for other possibilities, you could put an overdrive between the transmission and the transfer case, which would reduce the engine speed.  But there's the cost of the OD unit as well as new driveshafts.

Another possibility is an overdrive transmission.  In the case of a 460 you are pretty well limited to a ZF5, but that would actually work out fairly well.  If you go to Documentation/Driveline/Calculators and put in 4.56 for the axle ratio you'll see that with 33" tires you'd be turning these RPMs at 65 MPH:

C6 transmission: 3300 RPM

T19: 3000 RPM

ZF5: 2300 RPM

2300 RPM is not slow, but it is almost exactly what a truck w/a non-OD transmission and 3.55 gears is turning at 65 MPH.  Yep, my Big Blue did that RPM for many thousands of miles before I installed the ZF5.  And compare that to the 2700 RPM you'd be turning with a non-OD manual transmission or the 3000 RPM you'd be turning with a C6 - if you only went down to 4.10's.

So, a ZF5 swap would be something I'd consider were I you.  It might be less expensive and would sure be more flexible than going to 4.10's.

But, again, tell us more about what you have now and what you want to do.

Phew. 4.56 and a 460. Sign up for a gas station rewards card fast

How did you identify them being 4.56?

In addition to the specs the others guys asked for, aside from 'not towing much' what is the primary purpose of this truck?

Gas mileage aside, if you do a lot of highway driving and can get those rpms down (whichever route you take) the drive will be a lot more enjoyable.

Scott, that was the way the superduty welding rig was set up.
460/4.56

It is not uncommon, but 4.56 is more common with real truck tyres. (19.5, 22.5, etc)
The questions about lift, and rolling circumference are well noted.

Another thing to point out is this is above the carrier break.
So, the LOWEST ratio he can go is 4.10:1.
Beyond that he might as well just swap the whole axle and sell these to someone who's rock crawling or wants huge tyres.

ArdWrknTrk wrote

Another thing to point out is this is above the carrier break.
So, the LOWEST ratio he can go is 4.10:1.
Beyond that he might as well just swap the whole axle and sell these to someone who's rock crawling or wants huge tyres.

I was thinking of the "sell and buy different axles" but wanted to hear what he has first.
If he had a 6" suspension lift, 3" body lift and running 40"+ tires then I think that would not be the way to go. He is 16 after all LOL
Dave ----

See my comments in the 4wd C&C dually conversion thread just yesterday!  

Yeah, a lot depends on what you're turning.
Spreading a 10.25 without a special screw or hydraulic jack is a real PITA.
If anyone thinks a lifted, carbed 460 is going above 10(ish) mpg they ought to put the crack pipe down and step away.

I just don't see that going to 4.10's is going to be anywhere near worth it.
And you can buy a lot of gasoline for the ~$1200 it's going to cost to even get to 4.10.
Plus... you lose the acceleration.

ArdWrknTrk wrote

Scott, that was the way the superduty welding rig was set up.
460/4.56

Is that the 450 you parted?

I am curious about the history of his truck and how/why an 86 F250 4wd came to have that ratio as 4.10 is the highest I thought Ford offered then.

Yeah, that was the welding truck.
He didn't need to get anywhere fast.
And with a huge motorized welder, 120gal gas engined compressor, lift gate + service crane, 20(ish) 50# tins of welding rod, and whatever else, he needed those 10 lug dually axles.

Jim, you don't use a spreader on the 10.25" Sterling, the Dana 60, yes. I doubt he has a 9", the 460s were only put in the over 8500 GVWR trucks from 1983-1997. As for pulling power, Darth does quite well with the 3.55 gears and the original owner bought him for towing large horse trailers (four or more horses). I pulled a 10K 5th wheel with him and towing he actually got what is normal for an unloaded French 454 truck, 8 mpg.

Welcome to our little "asylum" and we will try to help you with information and resources.

Did Jack say he had an 85 1/2- 86?
Because before the running change in '85 M.Y. he would have had a D60 with left hand studs.

But maybe I missed it?
I'm definitely not seeing the forest for the trees sometimes.

Howdy Gary. Thank all yall for the helpful comments and here's a little more about the tuck. its a 1986 F250 XLT Lariat with a C6 tranny, 10.25" sterling rear axel, 4x4, with a beast of a gas guzzling 460. i'm planning on putting some larger wheels and tires on the truck, 33s, and I ran it up on a calculator which also put out 4.10 as I expected. I Also heard that im supposed to put a slightly lower gear in the front for 4x4, something like a 4.9?
        concerning the ZF5 swap, I would love to have a manual in my truck, however I don't have a doner truck for parts. I would love the truck to have a little more... yk get up. she's a torque monster and with a change in gears maybe that would help with some of the lack of a quick acceleration. I will be driving this truck to school aswell, which is only about 10-15 miles away, so a little better gas milage that a manual tranny and smaller gears would be greatly beneficial.

would swapping axels be a good idea in my circumstance? all im trying to do is make the truck less of a hauler (and I know that I probably shouldn't have got myself a 460 then but it was what was available lol) and just an overall better truck to drive regarding acceleration and speed. I responded to Gary about all the specs of my truck if you need em. Thanks!

You want to run 33's behind a C6?

Like Bill said his 3.55's are fine for hauling.
3.73's are another option. But either one will require new carriers and setting up from scratch.
Two R&P sets...
Carrier's another $250 each.
Plus a Master kit for each axle.
Plus a whole bunch of shims -and- time with marking paste.

Ultimately you will be time and $$$ ahead to swap axles and sell these on, to someone who needs deep ratios.

I have 4.10's from the factory with stock 31ish tires.
Overdrive has me turning 3k @ 80