Yes the front differential does have to come out. I will be regearing to 4.56s in about a month so we're kind ain the same boat. One thought that I had was that I would take the truck in and have the rear done, and then take it home, pull the front end apart and just bring the front diff back to them to save a few bucks in labor. I decided against that, but if you don't want someone else messing with your front end, this may be a viable option. I think I am actually just going to regear the front on my own. I have some experience with differentials, and the way I look at it is that the front diff barely gets used, so I think it is much less susceptible to break if not set up perfectly. I rebuilt my rear diff a few months ago and so far no problems. If I can do it once, I think I can do it again.

 

Man, that SUCKS!!! Actually one guy told me he'd have to see it to tell if he had to pull it, but I figured that was just to get me in the door. I'll have to think about some more, as well as research best place to get parts, brands, and 4.10 / 4.56. There is an ITP (Inland Truck Parts) REAL close to me, so I will be a lot more trusting of them than most. I worry because I have about turned every bolt on this baby myself so I hate to have someone else in there ****in around ya know? Good luck on yours...keep me posted if you like.

 

You seem to be pretty handy with tools; why don't you try to do the front on your own? If you drop the diff and decide you're in over your head you can take it to the shop. Then you don't have to worry about people messing with all your handywork.

 

If you have a manual tranny 4.56:1 is good. If you have an automatic go 4.10:1.

My son in law changed his axle ratio from 3.55:1 to 4.10:1 in November. At the same time he added a tru trac differential to the rear. He runs a 2003 XLT SCREW, 4x4, 5.4l, auto and 35" tires. He loves it. With this ratio the engine is not revving too high on the highway, but the truck still has good low end grunt.

If you want a LS seriously consider the Detroit Tru Trac (now made by Eaton). This LS is all gears (no clutches or cones to wear out). It is a good third member for a daily driver.

The 4.56:1 gears are too much, especially if you have an auto. Go 4.56:1 if you do a lot of off road driving. This is the ratio in my Jeep. It sees zero highway miles.

 

Depends on the tranny and OD ratio in your Jeep.
What model Jeep is it?
What tranny is in it?

The OD ratio on the autoboxes in our trucks is extremely deep.
My highway rpm with 31.5-inch tires & 4.10s aren't excessive by any means, as evidenced by the pics I posted.

There are guys with 4.88 gears on 35s & 37s who are still turning reasonable rpm at highway speeds with these trucks. I'd check out some of their posts.

4.56 with 35s will not be hugely different from stock rpm at highway speeds

 

My Jeep is a 99TJ 4.0 liter, 5-speed. But that is not a fair comparison if he has an automatic.

I guess reasonable RPM is in the eyes of the owner. Jackal did say he drives mainly highway. 35" tires he does not want or need 4.56:1 or 4.88:1, especially with an automatic. 4.56:1 would be great in a truck that sees at least 50% off road. 4.88:1 is great for a trail rig.

Jackal - research gears out a little more. You will regret paying big bucks for gears which spin your motor unneccessarily high on the highway.

 

Apparently all the guys with taller tires and even shorter gears are regreting their decision. As are the large group of guys with 4.10s on street tires, which nets me:
1900 rpm @ 60mph
2100 rpm @ 70mph
2500 rpm @ 80mph
...on a 31.5-inch tire.
Not sure how that can be considered excessive rpm in anyones book, especially since folks who've done this that I know, plus others I've read posts from, can't even tell a change in mpg (up or down).

In the end, methinks both Jackal and the OP may want to look at their setups, ask for some opinions, look at the data and then come to their own conclusions.

 

Hahaha...why the F aren't I getting notifications on this thread?

Anyway, I appreciate the discussion. I just so happen to also be the "OP". I have the 4.6L 4x4 with 5-speed tranny and 3:55's on 33" tires. (32.25" at best) I am leaning heavily toward 4.56's with a FoMoCo LS because it's only $200 as opposed to $500 and I haven't had that much trouble with the open diff. I do drive mostly highway, and rarely get to do any offroading, and NEVER anything serious. I just want more grunt and mpg's out of the truck. I have a pretty much wide-open exhaust, SCT tuning, e-fans, pulleys, intake, etc...so I want to increase performance. If my $1,500+ is better spent elsewhere, I'd like to hear it soon. Just got the W2's today so it won't be long. Since this thread, I've been winding it to nearly 3K before shifting and keeping it in 4th. gear till 60-65 mph so that has helped a LOT. In fact, I've even considered spending the money on the total Line-X encasement or just putting it toward the 2005 GP loan.

...or maybe that .50BMG upper for my AR. I'll add my sig. to this post just as a refresher on my mods. Well crap...forgot the sig lines got neutered sometime ago.

 

Alright, just wanted to "bump" this because cash is in hand and I'm still undecided. I was referred to a local ITP (Inland Truck Parts) which is a nation wide chain I guess. Any thoughts on ITP? I'm VERY nervous about having the whole front end and wheel / hub assy. raped. Alignment and another case of Royal Purple after break-in sucks too.

Also, still undecided on the Limited Slip and the actual ratio I want since 2WD trucks on street tires are running 4.10 and 4.56 seems popular for 4x4 with 35's. Maybe have a 4.30 custom cut for the front? Here are my actual numbers from this mornings drive into work rather than from memory.

70 mph / 2075 rpm (indicated)
75 mph / 2200 rpm (indicated)

I am pleased with the truck as it is, and I sure could put $1,500 to use elsewhere, but I have to ride the clutch just a little at take-off and with a full payload it's even worse. Better gas mileage would be nice too, ESPECIALLY better performance. I don't think I'll go 35's for quite some time, but I do intend to drive it into the ground. When the motor goes, would be nice to drop an "L" motor / tranny in there and cover the shifter hole up with an Expy console, but by then these items will prob. be VERY hard to come by.

Basically I'm sold on gears as a performance and fuel mileage mod, but I'm not excited about replacing functional parts at a high cost while inviting all kinds of trouble out of the work involved in the replacement. Seems like a MAJOR job on the front end. Damn you Ford and your 3.55 gears.

 

If this is what you are currently turning with 3.55, then a gear change alone will get you...

70mph:
4.10 =2396 rpm
4.56 = 2665 rpm

75 mph:
4.10 = 2540 rpm
4.56 = 2826 rpm

If a Lightning swap, or even adding a Lightning blower to your truck, is in your future, this thread has tons of links to Lightning guys and the gears they are running:
https://www.f150online.com/forums/sh...ighlight=gears

 

Thanks for the conversion there JNM...looks like 4.56 is way OVERKILL since I usually cruise at 75 - 80 so that's out. 4.10's or custom 4.30's for sure. Maybe the people at ITP can help ease my mind about the procedure so I can shut up about it.

ETA: I'm FINALLY getting thread notifications.

 

Well, ITP only takes loose axles, and my 4x4 shop wants $2,100 w/ an Eaton locker so I don't know...