Changing Rear End Ratio or OD Gear in G56

[CToney]

A friend has a '06 MegaCab 4x4 w/ G56 and his Milage isn't great. The overdrive ratio is only . 79 instead of . 73 like the nv5600. He was wondering what a set of 3. 54 gears would cost or if you could change the overdrive in the transmission?

The truck just revs to high for driving down the highway empty.



CR Toney

 

[bpenrod]

If you find a set of 3. 54 gears you will beeveryones hero!!

 

[Trizae]

I AGREE TOTALLY,,,, the more time i spend around thrid gen trucks the more i dislike them,,, and i sell them every day, no sound, ultra low gear transmission and 373 gears,,,, I could pull 8000 lbs with my 01 HO 6 Speed at 120 mph on 35's,,,,, never going to happen with a third gen truck,, unless you want a slushbox,,,

 

[Hercules130]

the mileage gets better. i'm seeing 17. just make sure to shift before 2000 rpm

 

[gsbrockman]

Replacing the OEM tires with aftermarket tires in a taller size would give you the same results for quite a lot less money... ... I'd try some LT285/70R17's in either the Mastercraft Courser A/T's or Discoverer STT's.

Greg

 

[Prairie Dog]

I'd suggest (while I'm spending your money) an overdrive unit, that way you can keep your ability to tow heavy and you won't have to change your front diff gearing as well.

 

[Bow66tie]

I sold my '93 D250 w/ 410s and bought my "disliked 3rd gen. " Let me tell you, I loved my old truck, but there is no compairison between the two. Driving my '05 is heaven. I also appreciate the gearing. I own a Cummins for one purpose, to haul. I wouldn't want it any different while using it for it's intended purposes. Anyway, who'd in their right mind would want to tow "8000 lbs @ 120 mph. " No one I know, nor would I want to know.

 

[GWBourne]

I sold my '93 D250 w/ 410s and bought my "disliked 3rd gen. " Let me tell you, I loved my old truck, but there is no compairison between the two. Driving my '05 is heaven. I also appreciate the gearing. I own a Cummins for one purpose, to haul. I wouldn't want it any different while using it for it's intended purposes. Anyway, who'd in their right mind would want to tow "8000 lbs @ 120 mph. " No one I know, nor would I want to know.

i agree with my fellow oregonian here... .

i bought 4. 10 with a 5600 and love it. around town mileage isnt bad and highway mileage is better with 315's. if he wanted mileage he shoulda bought a TDI. if he wants to be able to two and get decent mileage he got what he needed.





oh, i would go with some 315's on the truck and an overdrive. my plans will include an overdrive for around town running. i have never towed anything big or small faster than 70mph, and thats only when truck speed is 75. i dont have any need to go faster than that with a trailer.

Grant

 

[jelag]

I've got 3 of them myself (4:10 5600's) and love them... all 1 ton dually hauling... .



I bought a new F550 in 2000, worst truck I ever bought... . but we had it 150 miles and changed the rear end gears... . walked across the street and found gears for the same rear end used in a some other application... . cost like 350 for the set... .



I had to pull the tooth gear off the ring gear, and machine the new ring gear for it to fit. . it sent signals to the computer for the speedometer and ABS... . Dealer said the truck would never run right with the rear end change... . said the ABS wouldn't work... .



After a long thought... . we decided to buy the gears and do it..... no problems... . the dealer was all wet and never thought through the process... . I bettin that with the axle number you can find other sets of gears..... I'm also betting there is no changing the gear in the transmission..... today they build them one way... . and that's it..... its not like a truck transmission... .



I still own the F550... now has close to 350K miles and its on its 2nd engine and thousands in repairs... . but still is less than a new truck..... but I've got a standing order in for (2) 5500... . and my sales guy can't wait to firm up the orders... got my fingers crossed for another 10 months or so.....

 

[Turbo_Bob]

I have the NV5600 6 speed trans with a 1. 00 5th & . 73 6th, 3. 73 R&P and stock dia. 30" tires.



I would like to know what would be the cost be to change to a . 64 6th gear or should I just use 34" dia. tires and keep the trans stock?



Both combos will drop the 6th gear RPM around the same.



STOCK: MPH-RPM

1. 00 @ 60 = 2500

. 73 @ 60 = 1825

. 73 @ 70 = 2125



TALL GEAR: MPH-RPM

. 64 @ 60 = 1600 225 lower than stock

. 64 @ 70 = 1875 250 lower than stock



STOCK & 34" TIRES: MPH-RPM

1. 00 @ 60 = 2200 300 lower than stock

. 73 @ 60 = 1625 200 lower than stock

. 73 @ 70 = 1875 250 lower than stock



I know the drawback to larger dia. tires & rims are weight, but easy to do.

The 6th gear change will be more hassle and expense.



I get 21 MPG @ 70 MPH consistantly when solo (no trailer or weight in bed).

I get even better MPG if I drive 60 MPH, thats too slow.

I know if I lower the RPM's somewhat I should pick up some MPG.

 

[tobaccogrower]

i went from an auto 3. 73 to a G63 6 speed 3. 73 and i swore they mismarked the sticker and i had 4. 10's. 70mph in sixth gear is like 2400rpm. it's going to be great for towing my boat. i think this transmission needs a seventh gear!... . james

 

[MMiller]

I find it amazing, everybody preaches not to tow in OD, yet DC sets up a truck for towing that you have to run OD to get any speed out of it. I'd try and find a set of 3. 55's. Dunno what it would take to do it right. Just because a truck will tow loaded 120 doesn't mean they will. Heck gear the darn thing to drive nice empty, and tow in 4th unless your on the interstate. My old first gen runs 3. 55's and 305/70r16's (a true 33" tire). I haul loads up to 29,000#. On the two lanes 58 mph in 4th, she'll pull any hill around here, get her on the interstate, OD at about 68 and she tows great. The only time I think I need 410s is getting the load started off the shoulder of a road, but I always can lock in low side of the t-case and move anything. If my old truck can't tow it, the new ones can't either.



Michael

 

[GWBourne]

i agree that the DC guys are looney some times. i tow in OD and all runs well. im towing about 19k and use OD. now i just need to dually out my truck and go to 19. 5's

Grant