F53 4 speed vs. 5 speed, vs 6 speed transmission
Once you're rolling down the road in top gear, who cares?
Forum Discussion
Dale.Traveling wrote:
Well I do know that at cruising speed, around 60-65 MPH the 6 speed will be about 500 RPM lower than the 5 speed based on the final gear ratio. Less RPM less fuel usage.
Was talking with an owner that has the same chassis (18K Lbs) as mine and very close to weights loaded and he's getting 3/4 to 1 additional mile per gallon over me.
The OD gear ratio on the 5 speed transmission is ,71. The 6 speed transmission has 2 overdrive ratios .67 and .85. So if you're always in 6 the gear (.67) you might see slightly better mileage.
Another thing to consider is what the rear end gear ratio is. If you have a 16,000 or 18,000 lb. chassis the rear end ratio is 4.30:1. If you have a 20,500 lb. or 22,000 lb. chassis the rear end ratio is 5.38: 1. If you have a 24,000, or a 26,000 lb. chassis the rear end ratio is 6.17:1.
I would think the difference in the rear end gear ratio would have a more of an effect on mileage than the .04 difference in the final Overdrive ratio
