When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Turns out to the 2-speed rear end - High - Low rear axle had slipped between high-low.
The mechanism to the rear end has been broken for some time and has been stuck in low but must have become disengaged.