Hello
Many claiming 80 mph need to validate the accuracy of their speedometers, and the older coaches capable of 80 face serious disadvantages in driveability when the road rises in front of the coach.
A 1:1 transmission won't let you run that fast without screaming the engine to well beyond the "battle" setting....so forget about it!
Using Mallie's speed calculator
http://www.cwis.net/~mallie/page12.html 4.11 gear at 2300 rpm with 495 rev tires gives 68 mph
same at 2100 rpm gives 62 mph
economy cruise at 1900 rpm gives 56 mph
downshift point to catch 4th gear 1500 rpm gives 44 mph
3.7 gear at 2300 rpm with 495 rev tires gives 75 mph
same at 2100 rpm gives 69 mph
economy cruise at 1900 rpm gives 62 mph
downshift point to catch 4th gear 1500 rpm gives 49 mph
IMHO, your coach will have better driveability on secondary roads, with 5th being more usable at a slower road speed. I also suspect that 3rd gear will be more useful in town than a taller geared coach. Also, 2nd gear starts might be reasonably possible, if the weight is kept down in the conversion.
In town, the 5 speed sticks with the tall rear gear were a royal pain, there was no good gear to use. 2nd was too slow, and 3rd wouldn't pull out from low revs. Big difference from the 4 speed coaches, where 2nd covered the in-town territory quite nicely.
As far as real world fuel economy, unless you are blasting flat out back and forth on the interstate, two coaches operated side by side up and down and around on secondary roads, the fuel economy advantages, and the driveability advantages will be traded back and forth between them as to conditions in which short and tall gears are the more efficient. Net difference will be small, and in the right conditions, the 4.11 coach might use less fuel!
All things being equal, the 4.11 will pull the hills slightly better, and allow the use of top gear more often and longer than the 3.7 coach on secondary roads, defeating the up front gearing advantage of the 3.7 coach.
It sounds like you'll be very happy with what you have unexpectedly found!!!
Merry Christmas?
happy coaching!
buswarrior