I have a 1987 F250 and I want to change the rear diff to something of highway gear. I think I currently have a Dana 60.

Any suggestions?

 

Your rear axle is the Sterling 10.25. A simple search of Google should turn up a set of gears for the axle.

 

Make sure that the cost of a gear change makes financial sense. Your mileage might increase by 1 or 2 mpgs but it's going to cost ~$500 an axle to have new gears put in. You have to do a lot of driving to make up for the cost.

 

what gears do you have in there now? what motor and tranny are in the rig? what is the truck used for and is it 2wd or 4wd

 

A lot of F250's came with 3.55 gears that work pretty well on the highway. If you could find somebody parting one out, it would be cheaper & easier to do a whole axle swap.

 

I'm sorry but you simply haven't provided enough information about your truck to get productive suggestions. What axle gearing is in it now? What transmission does it have? Is it 2wd or 4wd? How big are the tires? How fast do you drive?

 

Although I appreciate that you want more info the amount of replies suggests that I have provided enough information, but since you ask - It is a 4x4 302 and the 4 speed that, I am told, is a Borg Warner. Also, the tires are big and that is all I can tell you but it came with 5 stock sized tires on rims that I intend to put back on the vehicle and sell the larger off-road application tires

I wouldn't mind doing a whole axle swap but I have had better luck with finding new gears than I have with finding whole axles plus I will need to swap out the front diff as well so right now I am looking ring and pinion sets.

 

with a 4 wheel drive you are looking at around $1000 for a gear swap.
get rid of the big tires and go back to stock size, and you should see a noticeable increase in fuel mileage.

 

Do not assume the rear axle is the Sterling 10.25, because some 1983/89 F250's came with the Ford 8.8" rear axle.

Some peeps refer to these F250's as a Light Duty, but FoMoCo did not.

 

Right there is what is killing your milage. Weak engine, NO over drive and Big tires

And if you dont even know what axle or ratio you have changing gears is WAY over your head

 

[QUOTE=TRJ021782;11091413]Although I appreciate that you want more info the amount of replies suggests that I have provided enough information, but since you ask - This comment is unnecessary if you want help be specific and give all information necessary, we are not standing there looking at your rig so HELP US HELP YOU

all this info below is your issue but like mentioned you need to figure out what gears you currently have.

It is a 4x4 302 and the 4 speed that, I am told, is a Borg Warner. Also, the tires are big and that is all I can tell you but it came with 5 stock sized tires on rims that I intend to put back on the vehicle and sell the larger off-road application tires
QUOTE]

 

Swapping diff gears is something I have done before just not on any ford (I always owned GM previously) and fear not I intend to to go back to stock sized tires and I even have a thread about the ZF S5-42, but as long as I am in there I might as well do a different gear in the rear.

Also - This may be wrong but I found an identification guide that suggests I have the Sterling 10.25. The misunderstanding comes from the prior owner telling me I had the Dana 60. Still interested in finding out what the ratio is.

 

you should have a tag on either the front or rear diff, might also show if you look on the door jam. this would all be mute though if the previous owner changed the gears at some point also. may have to do the tire rotation and count how many times the drive shaft rotates.

 

Another quick question, will a M5OD bolt right up in my truck?

 

yes with the proper transmission cross member, and driveline changes. might consider a zf 5 speed also. its a stronger tranny. still require above changes.