Taller gears

[87-250]

I don't haul many heavy loads so I thought I might be able to use taller rear end gears to improve daily driving fuel economy in my '87 F250. I haven't checked what gear ratio is in there now but what was the range of the rear end gears? For install I presume it's just pull the axles and exchange the gear cluster?

 

[5.0]

For install I presume it's just pull the axles and exchange the gear cluster?

This may sound like I'm being a jerk, but I'm not... if you need to ask how to change the gears, then it's not a job you are prepared to do. It's not like the old 9" where a preset assembly gets swapped out.

 

[87-250]

Well changing the rear end gears won't be a problem at any rate. What I really want to know is what gear options I have.

 

[LEB Ben]

^^^I'd agree with that statement. It's one of those things where if you're bound and determined to do it, you should probably have a mentor and practice. I'm not saying it's impossible for a first timer, but if you don't know the little things to look for and whatnot...best to leave it to a professional. After watching a few gear swaps and lending a helping hand, I decided long ago that I'd much prefer paying someone else to do that job. There's too much money involved and too much that could go wrong for to be willing to eat a several hundred dollars because I overlooked something.

 

[87-250]

Ok, I've been warned... But what I really want is the various gear ratios. No need to worry about my mechanical expertise any longer guys!

 

[LEB Ben]

Ok, I've been warned... But what I really want is the various gear ratios. No need to worry about my mechanical expertise any longer guys!

Do you want stock ratios or any available ratios? 2wd or 4wd? Is that a stock rear or has it been swapped over the years? One thing to keep in mind, if you go with too tall of a gear, you could essentially hurt you mpg's because it takes more effort to get the rig going and keep it moving. That extra stress also has a tendancy to shorten a trannies life.

 

[87-250]

Yeah, I want to make sure I don't overdo this. It's a 2wd and as I said in OP I haven't crawled under the truck yet to determine what I have. I was thinking around a 3.23 or something.

 

[87-250]

Forgot to mention that truck has orinal rear end and was orderred to haul a camper in mountainous terrain.

 

[Ridgerunner]

I have 3.06 gear in mine seems to do well with the 4 speed and 300 I6.

 

[5.0]

Forgot to mention that truck has orinal rear end and was orderred to haul a camper in mountainous terrain.

If you know it's the original rear, just check the door tag for the ratio.

 

[conanski]

Much depends upon the transmission, if you have overdrive you can utilize a higher ratio than if you don't have OD, but it also depends how fast you want to go. For general hauling duties 3.55's are a good compromise, but if you don't haul much, want to do some highway running, and don't have OD then something down in the 3.00 range is needed. But you'll have to check what's available from aftermarket suppliers for the axle in your truck.. which will likely be a Sterling/Ford 10.25 semifloating or full floater. I don't think Ford ever offered anything less than 3.55's in F250's so you won't find a 10.25 with 3.08's in the scrapyard.

 

[5.0]

I don't think it's been mentioned yet, but if you do the math on cost of gear vs. savings in fuel, you'd have to drive a whole lot for a long time just to break even.

 

[LEB Ben]

I don't think it's been mentioned yet, but if you do the math on cost of gear vs. savings in fuel, you'd have to drive a whole lot for a long time just to break even.

That's true...most guys go to a numerically higher gear to help their effective ratio and/or get more power to the ground. If you're sitting stock and attempting to drop, I think it would take a while to recoup and justify those costs...contingent on the amount you drive. With that thought factored in there, it would be waaaay cheaper to find an entire axle with the ratio you're looking for and swapping it in. With that, though, you're playing a game of russian roulette on what condition the axle is in.

 

[conanski]

It would be waaaay cheaper to find an entire axle with the ratio you're looking for and swapping it in.

As stated it's not at all likely there are any 10.25 axles out there with anything less than 3.55 gears, so in ths case a better solution would be to find an OD transmission to swap in.

 

[doc]

I'm rocking a 3.31 ratio in my '78 F-250.....good all around gear, but flies on the highway.

 

[87-250]

The truck has a 351ci engine, a "K" tranny (3 speed auto), and a "39" tranny ( which I presume is a 3.9). I was hopping to get a gear cluster from the boneyard and swapp it in. The other option would be a wholle read axle assembly. I don't haul too much and I don't want to "haul" as in speed. Just want to tame the trucks thirstiness. Thanks for all the replies. I wonder if a 1/2 ton rear end would be applicable or just a good way to screw things up?

 

[LEB Ben]

I wonder if a 1/2 ton rear end would be applicable or just a good way to screw things up?

The axle iteself won't make a difference, it's the gearing. Example... You can get 3.55's for just about any axle out there, ie a 9"...which is considered a half ton rear end, a Dana 60...which some consider a 3/4 ton rear end, or even a 10.25 which was under 1 tons. The only think you'd save by swapping rear ends are a few pounds.

 

[87-250]

Yeah I know a few pounds but if I can't get the taller gears I want for the type of rear end I have then the total axle swap may be the way to go. CONANSKI (Paul O) mentioned that if it is a Dana then options may be limited re: gearing. And this is not going to be a re and re swap just a possible bone-yard swap. Earlier comments stated that going in to swap out your gears is not for the faint of heart and I whole heartedly agree; easier to do brain surgery!