Unfortunately there isn't a service manual for the Twenty-Two, however the general principles for service and repair can be found in any of the manuals for the small Cat tractors, and I understand the 8C Twenty manuals is a very close match (someone will correct me on which version of the Twenty). But in any case, you'd remove the master pin from the rail on the relevant side and unlay the track, then undo the nuts retaining the final drive assembly to the transmission housing and using a suitable lift (e.g. a 2 ton Harbor Freight engine hoist) lift it off which will give you access to the brake band and the brake drum hub. You'll need a 20t hollow ram to remove and reinstall the hub but other than that, regular shop tools will handle everything else. You can get the brake band relined at a brake/clutch shop - I'd guess at 1/4" thickness for the lining which just needs to be glued on, does not require riveting these days. Be sure to use copper anti-seize on brake actuating shafts etc. and while you're in there, check the bearings for the hubs, and also check the thickness on the steering clutch plates.