The truck in my signature used to be a 5.4L and I re-geared it to 5.38's It was the best thing I ever did. I was running 38's with the 8inch lift and it brought my rpm's back down and was able to drive and tow with the truck again.

 

Another vote here for 4.88's and doing it yourself if your mechanically inclined. I regeared an 8.8 in my driveway. Just read until you understand. It's not rocket science, but it is a lot of work.

 

I'd rather just do what you did and swap the 5.4 for a 7.3 . But yeah that's what everyone says, and now I'm starting to think That I should've done it at the same time as the lift and tires lol.

 

You'll appreciate the gears way more now that you drove it this way.

 

thats very true, good way to look at it lol

 

Here's another vote for the 4.88 gears with the 35's or deeper gears if you are seriously thinking about going to 37s. I had a 2003 with the 5.4/ZF6 combo and I regeared from the factory 4.10 gears to 4.88 when I went to 315/75/16 tires and it really hit the sweet spot for the truck in my opinion.

 

My new to me '99 F-350 V-10 has 37's. Stock gearing was 4.30 and they were changed to 5.13 by the PO who happens to be my best friend and it did wonders for it. I would have gone 5.38 myself but the moron....I mean professional at Sutton Engineering who did the install said not to because it's a big block and they don't like to spin fast. There are numerous charts online that will give you the info you need to select the best new ratio. Generally speaking you want to go a little lower (higher numerical) if you want more pulling power and higher if you prefer high speed cruising manners. If you want it to accelerate as well as it did when stock you need to go lower than the equivalent ratio to make up for the weight and drag of the bigger rubber.

My truck does great as long as it's not hauling a heavy load, with my big *** cabin cruiser on it I really start longing for more gear reduction.

As for cost, I think it was just over 4K for gears and ARB lockers including ARB's largest compressor. The wiring and plumbing for the ARBs wasn't included, I did that part. Removing the lockers and compressor costs leaves it somewhere around $1500 for the gear change including all new bearings and seals, but he also had to drill the diffs for hoses and made & welded a plate to the frame to mount the compressor onto.

 

so ive decided on 4.88s, i think it will be perfect for me. but i dont know what brand of gears to get. id like to get a full install kit with all the bearings and seals etc, i mean if im gonna be in there might as well make it like new right? what brands are good? whats best for my application? if i do this, i want to make sure its done right. dont want to be going back in there. i was looking at this kit, and it comes with just about everything needed i believe. what do you guys think of this brand? it says 4.11 but in the drop down you can set it for 4.88. http://www.justdifferentials.com/02-...02-10-4.11.htm

 

Sounds like you made a very good choice with the 4.88 gears.

The formula doesn't lie:

New Diameter/Old Diameter x effective ratio = proper gear

With 37s

37/31.7 x 3.73 = 4.353 or 4.30 gears
37/31.7 x 4.10 = 4.785 or 4.88 gears
37/31.7 x 4.30 = 5.018 or 5.13 gears

With 35s

35/31.7 x 3.73 = 4.118 or 4.10 gears
35/31.7 x 4.10 = 4.526 or 4.56 gears
35/31.7 x 4.30 = 4.747 or 4.88 gears

 

its nice to have math prove you right now its time to figure out what kit to get, id like to get one with all new bearings seals etc. i mean if its gonna be torn apart might as well make it like new so i dont have to be tearing it apart again. any suggestions anyone? i was looking at a nitro gear kit. not sure of their quality though.

 

I've had good luck with USA Standard Gear.

 

I have always gone Youkon with no issues.

 

Yukons are reboxed gears.. So never know what brand your actually getting.

At least I knew that's how they use to be. I can't be 100% sure now.

 

what is your rpm unloaded at 65/70mph? mpg?


I currently have the factory 4.30's and have been debating between 4.56's and 4.88's.


I don't want to lose any mpg although it's hard to stay off the gas after the headers, 5 star tune and bbk throttle body. she's a beast!

 

RPMs (same loaded/solo) at 65 MPH are 2230 (2400 RPMs at 70 MPH) with the current 4.88/35" combo. When it had the same lift but 32" tires with the 4.88 gears it turned 2430 RPMs at 65 MPH (2600 RPMs at 70 MPH).
On a rare Interstate highway solo trip last year I set the cruise at 65-ish and saw 12.5 MPG with the current 4.88/35" setup.


Just curious, did you do the BBK throttle body change by itself? And if so what performance/economy changes did you see from it?