Groaning on tight turns is usually down to the TracLoc LSD.
If the Jeep is difficult to steer and really hopping on tight turns the viscous coupling in the transfer case may have siezed.
Get yourself a litre of 75W90 GL5 gear oil and a bottle of Mopar friction modifier.
Take the rear cover off (with a tray underneath to catch the oil). If the oil is fill of metallic particles (like glitter) your bearings are on the way out.
If the oil isn't contaminated with metal debris, refit the cover (seal with RTV silicone) and add the oil and additive. Drive the Jeep to the pub car park and drive some tight figures of eight to disribute the new lubricant around the clutch discs. If the problem is still there, you need to either replace the clutch disc package, or worst case, replace the diff carrier assembly complete.
Any further repairs require substantial dismantling of the rear axle. To remove and refit the diff carrier assembly, a special stretcher is required to open up the housing , releasing the preload on the bearings (although there are ways round this) and replacement of the clutch disc package is difficult but not impossible without the right tools. Although you can normally get away with replacing the carrier bearings without messing up the setup of the diff, replacing the pinion bearings, diff carrier or ring and pinion require specialist skills and equipment.
If you're not confident and equipped to do the job, I'd change the oil and if it needs further work entrust the job to a Jeep specialist or transmission shop. Don't be tempted to let any old garage loose on it unless you're confident they know their Jeeps or are transmission specialists. Don't go buying loads of expensive parts in advance. Get them to do the diagnosis first, then if they get it wrong, it's their problem. As a rule of thumb, to rebuild a Dana 35 rear axle should cost you around 4 or 5 hours labour at local rates plus parts and oils.
