I saved this information years ago:
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This is taken from an official Ford document issued 5/3/99. All the F-53 chassis' use a 5.38:1 ratio in the rear end - I supposed speeds could vary slightly due to tire diameter. In 2000, all the F-53s came with 19.5 tires.
There is no redline on the tachometer because the computer limits the max. rpm of the engine. The computer starts dropping cylinders to limit the RPM and Max speed.
"Advertised Power Ratings"
2000 6.8L 2v F53 Motorhome
Performance obtained and corrected in accordance with SAE J1349
F-53 Motorhome Chassis 2000 Model Year and Later
VEHICLE SPEED (MPH) COMPARED TO ENGINE SPEED (RPM)
MPH GEAR RPM
--- ---- ---
1st
5 - 900
10- 1600
15- 2450
20* 3250
25- 3970
30- 4800
2nd
20- 1880
25- 2290
30- 2830
35* 3260
40- 3600
45- 4130
50- 4500
3rd
30- 1710
35- 2050
40- 2350
45- 2600
50- 2900
55- 3170
57* 3250
60- 3460
Overdrive
40- 1630
45- 1850
50- 2050
55- 2270
60- 2450
65- 2660
70- 2850
Note: *Maximum Engine Torque (3250) occurs at MPH Indicated
Max. Engine Speed = 5260 RPM (Approximate)
Max. Vehicle Speed = 83 MPH (Approximate)