Ford super duty 3.31 rear end. Will it be a big mistake. ?
Pulling a 37 foot Cedar creek with a f350. Diesel. Would the 3.31 rear end work or should I get the 3.55?
Forum Discussion
^^^^At 25000 lbs and on 7% grade a 475 hp truck will pull down to about 58 mph. The difference in 3.31 gears vs 3.55 gears is this:
If the truck with 3.55 gears and 34” tires will be running at 2600 rpm in 6th gear it can put out 475 hp.
The truck with 3.31 gears and 34” tires will be running at 2800 rpm in 5th gear at about 56.4 mph and it will be putting out about 462 hp.
But if the hill gets a little steeper the 3.31 ratio equipped truck gains hp as it slows down where as the 3.55 equipped truck will loose power as it slows. So really both gear ratios will perform extremely well with loads under about 18000 lbs. once you get into dually territory 3.31s are no longer as desirable nor are they available.
If the truck with 3.55 gears and 34” tires will be running at 2600 rpm in 6th gear it can put out 475 hp.
The truck with 3.31 gears and 34” tires will be running at 2800 rpm in 5th gear at about 56.4 mph and it will be putting out about 462 hp.
But if the hill gets a little steeper the 3.31 ratio equipped truck gains hp as it slows down where as the 3.55 equipped truck will loose power as it slows. So really both gear ratios will perform extremely well with loads under about 18000 lbs. once you get into dually territory 3.31s are no longer as desirable nor are they available.
