I've been recently fixing up my old ford and I've been wanting to make it a little more drive able. It's a 1983 F250 with a 7.5l 460. It has a granny four speed manual with 4:10 gears. I know if money grew on trees I should just replace the tranny and transfer case but obviously I wish to go the "cheaper" route and get a gear swap. What should I go to If I wish to put on 275R16s and decrease rpms but still maintain decent speed off the line. I'd appreciate any help and I apologize for the long windedness.

 

what is your goal? Better MPG? I wish mine had 4.10s, the key is calculation,

1. gear changes are some what expensive, if it is 2wd your looking at at least 400 for gears and master rebuild kit and you set it up your self, x2 if its 4x4, about $14-1500 if a shop does it, calc one, can you make that money back in MPG? sure but ya better keep it for a while.

2. the 4.10s keep you in the power band making it more efficient light to light

3. If your carb is old, for 300 or significantly less you can replace it (or your ignition system and help your MPG without the gears.


Money=gas some folks want to change things by throwing money at it, sometimes that money is spent will never "repay" you

my 2 cents

 

If you do decide to change gears after reading the above advice, 3.55s should definitely work. The 460 and granny will get her rolling fast just fine. However an ideal swap will still be the 3.55/ZF since you can let the 460 slow down a lot in OD.

 

Mpgs would be nice but I'd like to go down the road and not do 2500 rpms at 55. I mean I don't even use my first gear. I just would like my truck to be more driveable and yes I plan to keep it for awhile

 

3:55s are what I'd be looking at going at to bring those rpms down considerably? Would my first gear be applicable now?

 

You might not need it still, I only use 1st on my truck if I'm hauling. I still highly recommend saving up for the OD swap, as the gear/trans change will have you at 2000 revs at 65 in OD aka mucho gas savings

 

How much would the OD swap cost me all together just so I know a ballpark area

 

I've got a '97 with a 460, E4OD and 4.10s. With the 0.71 OD of the E4OD that's the equivalent of 2.91 rears with no overdrive. I'm not sure how your older carbed engine compares with my newer EFI, but I think the 3.55 gears would still be pretty low with no OD.

And for that matter, I used to own an '85 F-250 with a granny low 4 spd and 3.55 gears and a '95 F-150 with E4OD and 3.55 gears. I towed up to about 5,000 lbs with both of those trucks (no huge, I know) and never thought either of those trucks were geared too tall, and they both had 351s.

I will say that I can't easily pull OD uphill with a load in my truck, so if you were to go to something like 3.07s you might find you need 3rd gear in that sort of situation. But driving empty I don't think you'd have much trouble even going that tall.

As far as 4.10s giving better mileage because the keep the engine in its powerband, you're running the engine WAY too fast for that benefit. You will get better mileage with taller gears.

That said, how much and how long would it take to pay it off? Hard to say. A lot of people claim that they can find a Sterling 10.25 with whatever gears they want for about $300. That's a cheaper way to get different gears (if you have a 2wd). Of course your truck probably has a Dana 60. I don't know how easy it is to find a taller geared Dana 60, or how hard it would be to swap a Sterling in.

 

I run/ran a 351M/ZF5 combo with 3.50 gears. Cruised down the highway at something like 1900 R's at 65 MPH. And it would pull seriously-steep hill on cruise in 5th. So a 460 could do that easily.

My ZF came from a 460 and I paid $500 for it, the t-case, flywheel, pressure plate, clutch, hydraulic clutch linkage, and front drive shaft.

 

I would do the zf 5 speed swap. It actually may be easier than a gear swap, and you would not lose anything you have now. I believe it actually fits in were the 4 speed is now with not much trouble, as long as your clutch is hydraulic. You will need to get a 460 zf.

 

I agree with Dave, but would add that you also need the transmission cover from the vehicle the ZF was in. The current tranny cover won't fit over the ZF as it isn't tall enough.

Also, I had to move the transmission crossmember back ~1", which required redrilling the frame. But, the original drive shafts worked fine.