Axle ratios
I've been looking at new F350's SRW and everything I see has the 3:55 gearing. My intent was to get the 3:73 but apparently I would have to special order it. So my question is: How much am I actuall...
Forum Discussion
Hi,
The rear axle ratio is picked out to give the best of both mileage, and performance. You will go up the hills a little faster when the engine RPM is higher, but get the best mileage at the lowest possible engine RPM.
So with modern 6 speed transmissions, you use the 3.55:1 rear axle and shift out of overdrive while going up a steep hill at 55 MPH!
I never really understood why anyone would want a 4.10:1 rear axle in a low RPM diesel truck. 3.55 is better. I had 3.73 with my 75 Ford and 3 speed, 460" engine. I would do around 2,500 RPM at 65 in drive, and 4,000 in second at around 70. It had lots of power climbing the 6% grapevine in second gear!
Fred.
The rear axle ratio is picked out to give the best of both mileage, and performance. You will go up the hills a little faster when the engine RPM is higher, but get the best mileage at the lowest possible engine RPM.
So with modern 6 speed transmissions, you use the 3.55:1 rear axle and shift out of overdrive while going up a steep hill at 55 MPH!
I never really understood why anyone would want a 4.10:1 rear axle in a low RPM diesel truck. 3.55 is better. I had 3.73 with my 75 Ford and 3 speed, 460" engine. I would do around 2,500 RPM at 65 in drive, and 4,000 in second at around 70. It had lots of power climbing the 6% grapevine in second gear!
Fred.
