Hey fellas...I'm still pretty wet behind the ears when it comes to being a mechanic. I currently have a 79 F150 4x4. It has a D44/9" combo with 3.55 gearing. It is lifted 4" and has 35's. I want to upgrade from the 3.55's to 4.56's. Now is where I'm going to show my ignorance, I've been told that my 'carrier' isn't 'big' enough to handle the 4.56's? Whatever that means? I thought gears were gears and you could swap in whatever you wanted to. So is there someone out there that can help me, and tell me what exactly needs to be done so I can regear to 4.56's? I don't plan on doing the swap myself, I just don't want to get ripped off by whoever does do it for me. Thanks for any help.

 

I believe that you are just getting a little confused with some terms, and what someone probably meant by "the gears wont fit".
This is not a size issue, it is an offset issue. Your 9 inch rear axle has no carrier break so you can install the 4.56 ratio with your current carrier, no problem.
Now your high pinion (reverse spiral) Dana44 front axle does have a carrier break. This break is above 3.92:1 ratios, so you will require a different carrier to accomodate the new 4.56:1 ratio.
This is a good time, to purchase a LS or other traction type device.
Your axles can "fit" any available ratio. The diameter does not change, but in order to ensure your ring and pinion engages properly, you will have to purchase a new carrier for a different ratio.
Good choice on gear selection.

 

Thank you sir for your help. SO the rears are fine no problem, an easy swap for someone who knows what they're doing. But the fronts will need the new carrier (is that what it's actually called) and then I can swap in the 4.56's. So that leads me to my next newbie question, do you have an idea of where I can get one of these 'carriers'. Thanks again for your help.

 

The "carrier" is the center portion of the differential where the large ring gear is bolted to. It makes the physical connection between the axle shafts and the input, or pinion gear. Wow, pretty scientific huh?
Well, the carrier can be open, or have many different types of limited slips, and even a locking type differential. A detroit locker is really a complete "carrier". A spool is a carrier without a differential, and is a direct connection.
Ok, where do you buy? Any shop that you are gonna buy your gears from will have access to any carrier that you want.

Check this out, you can find a bunch of reading here:
Randy's Ring & Pinion

 

Thanks so much I appreciate it, you cleared everything up for me. Have good one. Rep points given.

 

Anytime, and thank you back......