Rear gear ratio
I bought a 24 ft class c 1976 Holiday Rambler (E-350 chassis) last year, and recently had the motor rebuilt (ford 460). I ditched the motorcraft 4350 carb, and went with a holley 650 dp. I had them in...
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I'm on my third RV which is a 2019 Ford C with 4.56 and a 6 speed with double overdrive, so NA.
My previous RV was a SB Chevy with 4.56 axle and a Chevy TH400 (the GM version of a C6.) It was exactly as you describe. It did really well at 55 MPH (even with light towing,) but dropped off hard above or below that speed. When I had that rig I fantasized about re-gearing or adding an OD trans, but in reality I probably didn't have the power to support it (stock SB Chevy roughly 175 HP.)
My first RV was also a small block Chevy but 3.73 axle. IMO this was the ideal ratio for a non-lockup 3 speed trans with 3rd direct. This was my shortest and lightest RV of the three, but also was the oldest (1975) had the least HP of the three. But still it did very well on the highway 60-65 MPH and was a joy to drive even by modern standards. If you re-gear keep stock size tires and a direct-3rd trans I would shoot for 3.73ish. That's with me assuming Ford and Chevy from the same vintage are roughly equivalent. Just my opinion
My previous RV was a SB Chevy with 4.56 axle and a Chevy TH400 (the GM version of a C6.) It was exactly as you describe. It did really well at 55 MPH (even with light towing,) but dropped off hard above or below that speed. When I had that rig I fantasized about re-gearing or adding an OD trans, but in reality I probably didn't have the power to support it (stock SB Chevy roughly 175 HP.)
My first RV was also a small block Chevy but 3.73 axle. IMO this was the ideal ratio for a non-lockup 3 speed trans with 3rd direct. This was my shortest and lightest RV of the three, but also was the oldest (1975) had the least HP of the three. But still it did very well on the highway 60-65 MPH and was a joy to drive even by modern standards. If you re-gear keep stock size tires and a direct-3rd trans I would shoot for 3.73ish. That's with me assuming Ford and Chevy from the same vintage are roughly equivalent. Just my opinion
