Gears!!!!!!!!!!! My truck came with 3.55's. I put 34" tires on it straight off the showroom floor so never thought much about it. Well, my 4.10's are in. Driving factor to get the gears was due to new trailer, but shoulda done it for the tires a loooong time ago. This thing drives sooo friggin nice now I can't believe I went this long. Snaps through the gears. Driving down the freeway, or anywhere for that matter is effortless!! Torque converter stays locked all the time. Locks almost instantly after accelerating. Can accelerate from 40mph, already in OD, and the converter doesn't even unlock. Probably get better mileage since I'm barely pushing on the gas pedal to maintain any speed. I'm gonna get a friggin ticket!! Oh yea, it even fixed my speedo being off from the tires and stock gearing. WOW. Best money I have spent on this truck...Period. The change was not completely overwhelming when you first drive it. But after a few miles the subtle improvements really shine through. Highly recommended mod!!! Just thought I'd share.

 

I went up to a bigger tire on my 3.55 rear end and have wondered if this would help. Good to know that with 34's a 4.10 works good. I will probably wait and go bigger on my next tires and do the gears at the same time.

 

Thanks for the post Galaxy, just makes me all the more anxious to get my own gears done. It's good to hear positive feedback, as it makes me feel certain it's worth saving up for.

 

UPDATE...Just ran out my full tank of gas with the new gears under completely normal (for me) driving conditons. No towing or anything different from my normal routine.

I ended up with an INCREASE in gas mileage!!! I know there are some errors in the odometer give or take... but I easily drove about 40 miles further on this tank than ever before. I'll check again to make sure it's not a fluke, but the way the truck runs, I'm thinkin not!

 

Doesn't surprise me at all. Some people just can't wrap their head around the fact that lower RPMs do not always mean better gas mileage. Engine load and driving conditions play a far greater part and higher gears can often give you better mileage (under the right circumstances).

 

Hey galaxy. How much did getting those new gears run you? I'm thinking about getting a locking rear differential too. What kind of shop does that kind of work??? Dealership?

 

Stay away from the dealership and stay away from the generic 4 wheel drive places. I found a very reputable specialty shop in my town. All they do is gears, full on custom axles, etc. Paid $619 for the rear axle...parts and everything.

BTW...just drove out my second tank since the gear change. Had a lot more highway time this tank, but this time netted another increase in fuel mileag. 55 miles further on a tank of gas!!

 

did you do front and rear diff's. I want to get 4.10's as well so just curious.

 

No...I just did the rear for now. Financial reasons, plus the fact my truck hasn't been in 4 in over a year! Watch, I'll get stuck pulling that stupid traler now!!!! In all honesty...This is my 2nd new four wheel drive ford in a row. I've had a new Ford 4X4 of some type since '97. Not once...not one single time have I ever needed four wheel drive. Every time I've ever used that option has been for playing around of some sort....knock on wood!!

 

I know exactly how you feel. I have a 2001 5.4 with 34" tires. It came with 3.55's and when I first put the tires on I lost a bunch of power on take off. Highways didn't notice it as much. I figured out my city gas mileage since it doesn't see much highway use and I about crapped myself when I only got 8.5 MPG.

I went with 4.56' instead of 4.10's and it felt like somebody swapped a v10 in when I wasn't looking. I can take off almost as good in second gear as I could before in 1st.

My city mileage went from 8.5 to around 12 or so. I figured it out on a couple tanks cuz i figured theres no way it went up that much. But it did.

 

I went from 3.55 to 4.56 with 35" tires. The change is phenomenal. I gained about 3 mpg.

 

I have 35's on my truck and still have the 3.55's in my diff's also, but very soon I will be going to the 4.56's so its good to hear you got an increase in milage. I am getting 270 to a tank now which is putting me at 11 mpg. If I can get a few more mpg's over the performance gain Ill be stoked.

 

Originally my truck came with 3.55 on 255/65-17s

I now have on 275/55-20s

I don't think I need 4.10 but will 3.73s give me enough bang for the cost of around $650? Should I just go with 4.10s and will everything be ok with that?

 

what would it cost to put 4.10's in a 99 f-150... i believe i have 3.55's now...

 

Every shop is different. My grand total came to 1460 something, tax included. That is of course for a 4x4. A 2 by would be roughly half that. From what I have seen is 600-700 per axle is a pretty safe bet.