DDoyle

Reo Motors designed these trucks to have automatic front axle engagement via an overrunning clutch - usually called a sprag. Whe the rear wheels spin, the front axle engages. When positive traction is restored to the rear axles, the front axle disengages. In about 1951 a particular officer - whose names escapes me at the moment - began a crusade agains the sprag unit. Reo Motors, GM (who used a similar system in their M135) and Aberdeen Proving Ground all began extensive testing - which showed repeatedly that the sprag unit, properly adjusted, worked exactly as designed. However, proper adjustment was critical.

After about 20 years of debate, the air shift transfer case was introduced - it was more expensive, and no more effective - less so in some cases due to driver error - but had reduced maintenance.

Funny, the 5 tons were never subjected to all this largely unfounded scrutiny.

Best wishes,
David Doyle