4.56 Gears

wkpoor · Aug 4, 2008

Yep I done went and made the jump. They came in the mail today. Been thinking about it for a year now. I decided since my 3500 Express van is paid off and a new Duramax will set me back at least 35 big ones fuel mileage really isn't an issue. The new trailer pulls decent with the 3.73 I currently have but with a potential 14K behind me and only a 5.7 doing the work I'm going to give it all the advantage I can. Add up the total cost of the truck and trailer and I'm still 1/2 that of a new PU so again what little extra fuel it will burn is still money in the bank on this project. Anyone else have 4.56 ers and can comment on the performance gain?

rcowan · Aug 5, 2008

I put 4.56's in my 96 F150 4X4 and it really increased my climb capabilities.

The trailer with tractor doesen't bother the truck.

Fuel mileage tanked

john_bud · Aug 5, 2008

glug glug glug glug glug

Most engines are programed to enrich after 2000 rpm. Not a actual factual deal, but an observation that every time an engine is reved over 2000 the fuel gage drags me to the poor house.

wkpoor · Aug 5, 2008

glug glug glug glug glug

Most engines are programed to enrich after 2000 rpm. Not a actual factual deal, but an observation that every time an engine is reved over 2000 the fuel gage drags me to the poor house.

How fast do you think a $40,000 truck payment will drag me to the poor house? And that $40,000 truck still uses fuel too. My van is going on 7yr and it just turned 50,000mi so I don't drive it all that much anyway. But when I do its got a trailer tied to the back and that trailer just got alot heavier.

Chuck K. · Aug 5, 2008

Having regeard almost every vehicle I have ever owned I think you will really like the 4.56's. Is still have the stock 3.73's in my Dodge dually (wished I had went with 4.10's) and I run 4.88's in my jeep to help low end power loss from the 36inch tall tires. If your milage suffers more than you like you can either slow down a bit keeping RPM under ~2K or possibly fine tune your final drive ratio by going to a slightly taller tire to find a happy medium..

john_bud · Aug 6, 2008

wkpoor said:
How fast do you think a $40,000 truck payment will drag me to the poor house? And that $40,000 truck still uses fuel too. My van is going on 7yr and it just turned 50,000mi so I don't drive it all that much anyway. But when I do its got a trailer tied to the back and that trailer just got alot heavier.

Who said buy a new one?

I said keep the rpms under 2000...

wkpoor · Aug 6, 2008

Any other truck regardless of cost will never be a payback against a couple of miles to the gallon loss on the van. In these economic times making do with what I have will win out over any purchase of another vehicle. Besides if I where to make a change it would be to buy another van with a Duramax and finding one of those in good shape used would be next to impossible.

crashz · Aug 7, 2008

I think as long as the engine is tuned (you'll proabably have to have a custom program uploaded or new ECM chip) and the tune incorporates the new gears, I bet your mileage will not be much worse. Could even be better around town as long as you keep your foot out of it. You will definately lose highway mileage, but with 50K miles on a 7 year old van, my guess is that you spend very little time on the highway just cruising around.

wkpoor · Aug 11, 2008

I made a bunch of calls today to try and figure out the speedometer change issue. Dealer was of no help at all. Go figure. It was like I was asking them if I could drive to the moon and what gear would I need.

Anyway I found a couple of businesses that may be able to help me. They specialize in recalibrating and/or retuning ECM's. One guy said I can outright buy an ECM from him already setup for speedo and transmission shift points programmed in. Basically plug and play right out of the box by sending him 160 bucks and my VIN#. Other option is to buy my own power programmer and go at it myself. I feel I need to line these duck up first or this mod might not turn out well for me.

crashz · Aug 12, 2008

Good thinking wkpoor. I would first check out any performance shops in the area and see if there is a local tuner that can do the programing to your needs. The mail order tunes are usually pretty generic and meant for a general performance gain only. By paying a local guy to tune it for your particular driving style, you may not take a hit on mileage at all. And with the 4.56's and custom tune, that van will be a towing monster!