Well it looks like I am going to have to rebuild my 8.8 sooner than I thought. I am pretty sure my rear has 3.55. I would like to do 4.11 but I am told they are bad on highway speeds and gas. So I will probably do 3.73. Will I be able to tell a difference? My truck is so sluggish and I want more go. Now if I keep the front 3.55 and my rear 3.73 is that okay? Do I absolutley have to change both to use 4x4? I would rather save money and do that but if I have to do the fronts I will. Thanks so much for the help!

 

With the tires your running in the pic i'd say only go to 3.73 the 4.11 s would be better if you had 33 in tires or bigger on the matching of front and rear gears it would probally be best to have them the same. but if you 4 wheeling in mostly soft terrain(ie mud or sand)you could probally get by a while with different gears. the front is a little difficult to change so it will cost more.

 

If nothing has been done to the rear, then yes it is 3.55, and the front is 3.54. I would recomend going with the 4.10, or even 4.56, you'll be happier. And yes, even with 3.73 gears you would need to change the front, too, eventually. You didn't mention what tire size you have. But 4.10 gears and 33" tires will balance out the milage and 35" tires will balance out the 4.56 gears. I just rebuilt my rear-end three weeks ago myself. I put in an ARB and 4.56 gears. I have not been able to change the front yet. Can't go wheelen yet until I do that

 

If you do not change the front gears, you cannot (cannot) use your 4WD. Imagine: With 3.73 in the rear and 3.55 in the front, your rear wheels will be spinning about 6% slower than the front. If you do this in loose dirt, there will be some forgiveness, because the wheels will be allowed to slip. If you hit anything high traction, however, you will introduce severe driveline bind, and something will give. Usually, the t-case or something similarly expensive. 6%doesn't seem like much, but to your driveline it's the difference between happiness and disaster. You can imagine the havoc this will play in your drivetrain.

It seems too expensive initially, but really it's way less expensive to change both gearsets now than it is to fix what broke AND change the gears.

And what year is your Bronco? Does it have overdrive? 4.11's are a fine choice for a regear if you're looking for more low-end power. 3.55 to 3.73 is not a really significant change (only 6%). Remember, changing gears doesn't give you more power, it just moves the power band to a more usable range. If you ever go to larger tires, you'll really appreciate the lower gears (numerically higher).

 

Hey thanks that really helps. My tires are 31's and I am satisfied with them. If I were to go to 4.10 would I be able to hit the interstate at 80-85 without binding out my engine. I do have an AOD.

 

What is the milage like with 4.11s and 33" tires? What is it like on the highway? Right now I have 3.55s and 33" tires and was thinking of going to 3.73s for a bit more torgue, but perhaps I'll need to go to 4.11s as well. I really don't want to turn my truck into a beast thats ill maner on the highway.

Thanks

 

My Jeep, for example, has 4.88's and 35's, and runs just under 3000 RPM at 80 MPH. With 4.56 it would be 2600, and with 4.10 it would be around 2250

My Suburban with 4.10 and 32" tires runs at 80 all day long at 2400 rpm in overdrive. My overdirve is a little deeper than the AOD, though.. Say 2500 - 2600 rpm for you. Very acceptable. With 33" tires it would be 2200 - 2300 rpm or so.

 

Ya I think you are right. I only take it out of town maybe every 6 months anyways so that is the route I thinK I will go. Now I just have to figure out what credit card I am going to put the $1400 bill on.

 

So whats the gas milage like, befor and after the gear change?

thanks

 

If you don't change your tires and you go to a lower gear, your gas milage will decrease somewhat. Not a lot, but you'll notice. Your engine will turn faster for a given speed, so you'll use more fuel.

It's not like our trucks are milage champs to begin with

 

if you 8.8 is shot i would find a 9" rear to swap in. the 8.8 is crap rear end and will continue to give you problems. the 9 is much stronger and easier to upgrade. I installed a 9" out of an 80 bronco. it bolted right in i was even able to use my rear brake hardware off of the 8.8 and the driveline bolted up perfect. if you break an axle on the 8.8 your tire will fall off, but with the 9" you could still drive home this is a big plus. check out my superford page for pictures of the 9" swap took about 5hrs and was easier then a motor swap for sure.

late

 

8.8 is no stronger than the 9", its just easier to dissasemble. if you where worried about loosing axles, id just keep the 8.8 and install some Fordracing Axleretainer kit (somthin like 70$)

 

Keep in mind the newer Bronco's with ABS have a tone ring in the 8.8 rear end for the ABS, and if I remember correctly it is also the speedo pick up as well. So changing to a 9" would not be an option.

 

I have been thinking about a question like this too for a while. I have 355s and 31 inch tires. I don't plan on a lift or big tires anytime soon, but I do tow with my truck and it is a little slughish getting going, even without the trailer. Would 410s be to much for 31 or maybe 32 inch tires? I do drive on highways but the fastest I go is about 75. I am concerned about gas mileage, so if 410's would knock me from 12-13 to under 10 or lower then I would have to pass. I am thinking about something in the middle, but if two years down the road I change my mind about a lift, which is quite possible I don't wan't to have to pay to get it redone again. thanks for any suggestions

 

The answers are in the replies above. Yes, your milage will go down. Not below 10, but probably to around 11-12. 4.10's are perfect for 31" - 32" tires if you have overdrive.