Is your truck running on stock size tires and with or without a lift? 4.88s are pretty deep gears unless you are running large tires and/or hauling heavy loads. A switch to 4.56s would help you out but IMO its not going to be as dramatic of a change unless you were to drop down to 4.30s. It kind of depends what you are using the truck for, which judging by the fact that it is a F450 and your username is pullingheavy you may want to keep the steep gears. Its a tradeoff as to mileage and rpms v.s. streetability and towing power. You will hear about as many different opinions on this topic as there are members on this forum, however a bit more info may help to narrow it down more.
am running 225/70/19.5 which is stock, no lift at times I load up to 16,000lbs and pull a 7x14 enclosed full of tools and parts but tthis part of my life is soon to end and I want to take the dump off and do a flat bed and just tow 5th/goose neck. so maybe 4:30 would be good.
JMO, but dropping from the 4.88s to a 4.56 isin't really worth the money is basically what I was getting at. I am running 4.88s on 40s, and I actually think it would have been better in my case to run 4.56s. I think in your case running on stock tires and no lift you should be fine running 4.30s with plenty of pulling power for a 5th. While picking up a bit more mileage and less rpms at the same time.
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