To folks with larger than stock tires...

[JustWondering]

Has anyone with 285's or larger tires considered lowering the rear ratio of your differential to get some of the off-the-line-power back than say vs getting Juiced or Duramaximized. Hmmm, JustWondering....

[JustWondering]

I apologize for posting off topic, should have posted in the drivetrain section. Slip of the finger....sorry.

[SoCalDMAX]

I'm running 255/85s and they're roughly the same dia. as 285s. I did notice a slight loss of acceleration when I changed, but not enough to warrant a change in gears. I'm interested in better fuel economy by keeping the same ratio and adding a 6th gear when that becomes "enabled".

I was interested in more power and it has worked better than expected. It stays in 5th unless the pedal drops to the floor. I can get to any speed, just short of "exhibition of speed", using 1/2 throttle or less.

I'm curious why you're interested in gears rather than a little extra oomph, just being open minded.

Regards, Steve

[hdmax(mike)]

From what I have read 3.73:1 and 4.10:1 are the only differential gears you have to choose for the Duramax. equiped truck. ( 3.73:1 is the only choice from the factory) And I would bet that a swap for the 4x4 would run you close to $2000 installed.

So an engine mod would be much cheaper.

When and if I lift my truck and put 315/75/16`s or bigger, I would like something like 4.30:1 or 4.56:1 gears.

[BowTieDmax]

Hum ?? 4 bald 305's , 4 trophies out of 4 truck pulls this year. Hot Juice !! I see no power loss. Life is good !!!!!!!!!!!!!

[SoMnDMAX]

I've considered changing to a 4.10 gear, but the cost of the gearsets and the amount of time it'd take for me to install them is not worth it.

I'm quite happy with the setup I currently have. With the big tires I get a slightly lower (numerically) ratio on the highway, which increases mileage. If I need to have "higher ratios" I just turn on some fuel... :D :D :D

[Silver Bullet]

BowTieDmax,
What rims are you running those 305's on? I hae been tossing around the idea of going with 305's on my next set...I still have 20K or so to go.

[sdaver]

ditto four bald 305's with 17k on them ........9.103 1/8th mile @74mph.....good here to......dave :D

[bryantch]

i noticed some of you are upsizing tires for fuel ecomomy...i change tires sizes for higher load carrying capacity and the fuel econo is a bonus. unfortunately my particular truck got 14 mpg around town with 265's and when the tech bulletin came our regarding oversized tires i changed back to the factory tires and now get 16 mpg (the truck has had some "issues" so the dealer tech suggested the change back for warranty reasons). i keep very accurate records of fuel economy and even factoring the increase from the "oversize" tires the economy is still less than with the factory tire size. so now i have a relatively new set of 265 wrangler mt sitting in my shop.

i cant imagine the economy loss from larger tires , much less the additional probs with this particular tranny. i have also considered the ring/pinion swap for the new 03 as a result.

[Tommy turbo]

I put 285's BFG's on my factory wheels and I love them. I thought I could notice a little less off the line power at first, but cannot tell a thing now,(5000 miles). My milage is exactly the same.(18 MPG). Just returned from a 1800 mile trip pulling a 32 foot bumper pull Travel Trailer to the mountains of CO. my milage averaged 9.8 for the trip. best of 10.6 and worst of 8.5 per tank. The way the tires made my truck ride and LOOK I would not change a thing.

[BowTieDmax]

SilverBullet,
I put my 305's on my factory alloys. Yes the rims are to narrow for the tires but when I bought the truck I wasnt sure if I was going to lift the truck or not. But I knew I had to get them pizza cutters off so on went the 305's.
I run about 35psi empty/50psi loaded and that seems to help keep the crowning down. I've got 36,000 miles on them and the wear isn't to far off from being evenly worn/bald across the tire.(THANKS HOTJUICE!!) I just called 4wheelparts yesterday to see how this 50,000 mile tread warrenty works. Because they need replaced before the snow flys. Paul

[imported_]

I replaced my stock 245's with BFG All Terrain 265's & have lost at least 2-3 mpg on the highway so far. How are yall upsizing your tires & getting better mileage?????

[2L MAN]

FISHNGN- Has your MPG actually decreased, or does your odometer show lower mileage than the vehicle actually traveled? This is typical as the larger tires slow the speedo/odo, actual speed/mileage is higher than shown. MPG can increase because RPM decreases for a given speed, ie: taller gear ratio. I run 315/75-R16 with a superlift speedo recalibration unit. I like where the powerband is now over stock. 70 MPH approx 1800RPM. Also when in 4th gear towing uphill it's right in the powerband- not revving to the moon. Just my take on it. smile.gif

[2L MAN]

FISHNGN- Has your MPG actually decreased, or does your odometer show lower mileage than the vehicle actually traveled? This is typical as the larger tires slow the speedo/odo, actual speed/mileage is higher than shown. MPG can increase because RPM decreases for a given speed, ie: taller gear ratio. I run 315/75-R16 with a superlift speedo recalibration unit. I like where the powerband is now over stock. 70 MPH approx 1800RPM. Also when in 4th gear towing uphill it's right in the powerband- not revving to the moon. Just my take on it. smile.gif

[imported_]

I have calculated that every 30 miles i travel that my speedometer is off approx. 1-2 miles. I checked this with my Garmin GPS while driving. Also when iam going 70 mph my GPS shows 67-68 mph. Does this sound rite.? So maybe my mpg is still correct then....

[?DURAMAX]

Don't even bother. I have a 6"RCD lift and 35" tires. I do have my exhaust done and the juice. My truck never even comes out of fifth gear. Plus still get 16-18 mpg.

[JustWondering]

Steve, sorry it has takan me this long to reply to your question...too much workie.
Reason for my interest in gears ~ Like you, I also noticed a loss in acceleration when I went to 285's, not much, but enough to make me not too happy when I drive the truck.
I guess at the time of posting the question, I didn't realize how much a set of gears would set me back ( thanks hdmax )
I know that the Juice is very popular in this forum but in my opinion, at this time, it appears to be a little too unreliable. Too many users are reporting problems with this module and Edge seems to be coming out with a new version every few weeks.
And you folks have spooked me off the Duramaximizer, I don't want fuel leaking all over my engine.
Well, I guess for now I'll just wait'n see what Banks will be coming out with and/or if Edge finally works out ALL the bugs outta the Juice.
Thanks all for your help!