Hi,
Here’s a link to the [http://www.britishexplorers.com/Kenwood%20gearbox/A701a%20service%20info.pdf|service manual] for your mixer.
Here’s a [http://www.britishexplorers.com/Kenwood%20gearbox/homepage.html|link] that may also be of some use.
Hopefully they both are of some help.