Does or has anyone installed 4.56 in their lbz or any duramax I'm having 4.56 installed and i'm running a 37" toyo tire but 4wheel parts said i should run a 4.56 in the front and like a 4.63 or something close to that in the rear has anyone heard of this. Also how was the improvement in performance and gas milage I would love to head since my truck wont be done til the end of the week and i'm dying to find out any info appreciated.

the 4:56 for the front is a tad shorter than the rear 4:56 It least it use to in the older trucks with the ifs in the front now it may have changed.Bottom line dont listen to that guy go to some one else.The front and the rear should be the same.do not mix and match.I also plan on having the 4:56 installed on my lbz soon.The reason the front is a tooth off from the rear is to give the front slightly more pull when stuck so the weight of the front pulls better than the rear trying to push the whole truck.Hope the this makes sense and if I am wrong I'm sure some one will correct me.

i have 4.56's. do not mix and match your ratio's.that is a recipe for disaster. follow sickpuppy advice and go somewhere else.i would be very "suspect" of someone that told me to run diffrent ratios f&r.....it will perform like the truck did when it was stock. maybe better with the 37/4.56 combo. however you will lose some gas mileage. i lost about 2.75 mpg but i have 38/15.50 tires that are wider than 37's.how much gas mileage you are going to lose is going to depend on you, and the truck, and what you do with, and your modifications

fill out your signature so we know what mods and kind of truck you have so we can help you better.

they only time i see running diff ratios f/r would be in mud drag racing. were you would want the front to turn slower than the rear. anything else should be the same.

I plan on putting in 456 my friend from 4 wheel parts said opposite 456 rear 463 front.They dont make 456 front and rear and that they are close enough not to bind.

i had my truck done last week and loved it till i blow another hose so it is in the shop agian i don't have any type of MPG to report because i didn't even get a 1/4 tank out of it but performance wise felt a little quicker off the line then when i was running 35" with the 3.73 i hope my mechanic doesn't take to long i want my truck back so i can have fun i have forgoten how much less power a 1/2 ton has it sucks and ya stay away from 4 wheelparts i have heard to many bad stories about them a buddy of mine has had his truck in 4 times because the gears keep messing up and he breaks them in like you are suppost to

The difference between 4.56 and 4.63 is less than a 5% change and won't hurt anything. I have 4.63's in the rear of mine and 4.56's in the front. No issues but I don't run my truck in 4WD at 60 MPH either.

Whats your MPG lxh0318 did it increase or decrease with gears? I havent regeared and get 9mpg around town.

Slightly taller front gears improve off-road performance. Hard surface driving would put a fair bit more stress on the driveline.

Gear cost me around 3mpg. I was getting 16mpg but now I am down to 13 wether I am in town or driving 70mph.


Whats your MPG lxh0318 did it increase or decrease with gears? I havent regeared and get 9mpg around town.

they only time i see running diff ratios f/r would be in mud drag racing. were you would want the front to turn slower than the rear. anything else should be the same.Actually,I think they run the front end slightly faster to clear the mud and help it track straighter.

LXH? your saying your gas milage got worse after you put in gears with your 40's. Shouldn't of it got better or did you regear before the tires. I am now getting maybe 2-3 mpg better than i was. My truck is faster, I am running 37" tires on 24" wheels but i haven't seen 40's for 24" wheels yet

Gear cost me around 3mpg. I was getting 16mpg but now I am down to 13 wether I am in town or driving 70mph.

I just recently regeared my truck to 4.56 with 40's, although I have only put on 200 plus miles on it the mileage seems to have went up at least 2 mpg. Could it be that you have a LLY and the rpm's are different from the LB7?

From what i have been told in the past by Gearing techs is that you shouldnt run more than .03 in a ratio. Example would be 4.09-4.11 would be withen spec., but say 3.50-3.55 would be out. This is of course for street use. I have ran gears in my off road truck that were out of spec. "4.10 front-4.20 rear" with little problems in the dirt or mud but as soon as you drove it on the street it would bind right up. So it comes down to what you are doing with your truck and how much you want to work on it due to breakage or premature wear.

just did the 4:56 love it.No mileage to report yet.Definitly worth the effort.My second gessing was for nothing.Increase in rpm 500 just what I expected.:ro) :rocking:

mine only increased 200 what size tire are you running sickpuppy. but now that i have had a chance to run the truck it runs much better and towing is still a breeze for this truck doesn't seem to lag or anything and when you get a ford guy up next to you that tries to pass and i just give it a little you can tell he is mad

On the street, I would recommend they be the same or damn close. On our tractor, the front is a different ratio (1% diff) to pull better on loose material and thru turns.

DEWFPO

I'm running 33s x12.5x20

I just recently regeared my truck to 4.56 with 40's, although I have only put on 200 plus miles on it the mileage seems to have went up at least 2 mpg. Could it be that you have a LLY and the rpm's are different from the LB7?


so what kind of mileage are you getting?

Sickpuppy do you think the 4.56 was a little to tall for your 33 inch tires how has your milage and performance and do you know what your top speed is now just curious?

4.56 are too tall for 33's .your truck must be screaming at highway speeds.

Unless your towing daily I'd go 4.10's with 37" tires.

with the 6speed the truck is more responsive the milege has gone up 1mpg so far Im having to much fun putting my foot in it.:cool_shad

well thats great you do know you overgeared i was worried about my 37's and 4.56 but its been good im sure you quik off the line but probobly rip them loose easily next you need a good tranny

so what kind of mileage are you getting?
I haven't kept track since I have to manually log the miles in, as soon as I come up with some information after 3 full tanks I will provide those numbers. As of right not it appears that I have gained at least 2 mpg but will provide better results.

I'm running 4.56's front and rear and had a question for everyone that went with the same or lower ratio. Did anyone else go through the brake light/ABS code faults?? Just wondering if anyone came up with a true fix for this. I bought Superlifts ABS corrector and Tru-Speed mod and they corrected my speedometer, but my instrament panel still lights up when I come to a stop. Use to make my chimes go off too, but I killed that a long time ago.:snipersmi

Sounds like a job for a tech 2 scanner or could be cured with EFI live perhaps. I have a 4.56 in the front and 4.56 in the rear the dealer said they wouldn't gear them the same. I have gained 2 mpg since i regeared and have noticed increase in power to the ground all over the speedometer. Truck seems like its not working as hard to maintain speed.

ya i haven't found anything that will solve the problem easy so i am saveing to get EFILive in the spring but for now i just deal with it i don't have the factory radio so i lost the chimes along time ago

EFI Live will help with this problem at least that's what I have been told. I'm getting a tune and EFI live installed on Monday and currently have the same problem with the ABS light. Once it is installed I will let you know if it removes the ABS sensor.

Yeah let me know how it turns out and what actually takes place. There probably isn't a way to fix our situation with the ratio/tire size and still have the sensors work for a true problem. Sounds like you have to disengage the entire sensor via a tune. Am I correct in saying this, or does anyone know of a way to fix the problem but still have the system function correctly.

Craig

Yeah let me know how it turns out and what actually takes place. There probably isn't a way to fix our situation with the ratio/tire size and still have the sensors work for a true problem. Sounds like you have to disengage the entire sensor via a tune. Am I correct in saying this, or does anyone know of a way to fix the problem but still have the system function correctly.

Craig

No, from what I understand, you can just block only those codes from coming up. Hence, no more lights. Haven't needed to do that yet, but Im planning on going with a bigger tire in the future.

once it is recalibrated and you tell the truck it has 4.56's and bigger tires the light will come on. you have to trick the truck and use the stock gear ratio and the closest tire to stock as you can get and have the ratio correct. as an example i have a predator and have it set for 3.73 gears with 265/75/16 tires to get the speedometer correct.

i did the same thing and a correction i have 4.63's in the rear and when my gears were put in my speedometer was correct with my xcelerator adjusted for stock tire size and stock gearing no lights no problems

I need to clarify, when I said I went up 500rpm over stock.I should have said I went up 500rpm with the tires I have.Before the gears 1750 @75 now 2200@75 I took delivery of the truck with the tires and lift so I never saw the stock rpm at any speed.

So if you just tell the ecm that it has a stock setup with a programmer, then the rest of the ABS system should function properly, you just don't have the irritating lights and buzzers? I wish my Edge had the capability.

http://www.differentials.com/calc.html

Problem solved with the ABS, after Pat (McRat) tuned my truck he then took a Tech 2 and recalibrated the speedometer with the new tire size and I believe left the gear ratio stock and this eliminated the ABS light to come on. Apparently EFI Live has cannot communicate with the ABS sensor it is seperate from the ECM and a Tech 2 is required to do so.

The only reason they are different is design parameters on the differentials. Because of variations in flange position, ring gear thickness, and ring gear OD they use different combinations of teeth. Sometimes mud bog guyus will try and get the front to spin faster than the rear as it helps pull the truck through straight. But for a regular 4x4 they need to be as close as possible, but as note, 4.56 and 4.63 are close enough. My Jimmy has 4.09 in the front and 4.10 in the rear because that is what is available in that family of diffs.

yah I am really worried about 4wd drag racing when i get into high speed on tar in 4wd with the different ratio