90's?
I just sold a '94 Grand Cherokee (GC) to guy that's using it as a winter beater. Still ticking.
I'll comment on the GC's specifically, though the Cherokee's shared much of the same with the 4.0 trimmed GC's
The GC's will both have solid Dana30's upfront. At this age I'd be looking at the balljoints. Drive over uneven/bumpy roads and listen for pops. If it has U-jointed front axle shafts, check those for leakage and wear on the crosses.
Check the tierods all the way up from the pitman arm to the balljoints for evidence of greasing. Some years had greasable joints that many owners often neglect.
Loose steering can also be caused by wear in the steering box, the box can be adjusted, to a point. Check the condition of the fluid, the box isn't cheap.
You'd typically find the 42re tranny in the 4.0's and 46rh in the 5.2's. 46rh is, not surprisingly, more robust. If you run into a 42re that shifts rough, hard or lazily it may likely be that the throttle valve (TV) cable is simply out of adjustment. Many owners don't know about this and get swindled by trans shops.
GC's had 242 and 249 transfer cases. The chain driven 242 cases had selectable 2wd, 4full, 4part time and 4lo. The viscous coupling 249's had only 4full, 4part and 4lo. The 242's hold up fine over time but I would check that the linkage still moves (many are rusted solid from lack of use) and that the front and rear prop shaft seals aren't bleeding oil. The 249's generally go out to 100K before the viscous coupler locks up, drivable, but the front axle will bind in tight turns. Perform figure 8's on dry pavement to confirm this. A new viscous coupler alone is ~$400, not to bad to DIY though.
For the rear axles you'll find Dana 35c's and 44a's. 4.0's typically sported the 35c's and most 5.2's sported the 44a's. Many 35c's, at this age, will show signs of spun axle tubes or broken plug welds at the axle tube/center diff interface. Look for an oily residue at that interface, no fix for this. If you see a 35c with gear oil dripping out by the tire this means that the tube seal has failed likely due to the bearing failing. If the bearing has failed then the axle shaft on that side is also likely done ($). Leaking pinion seals are another common problem at this age. The 44a's were more robust but the center section, being made of aluminum, was prone to scratching on rocks. Bring a magnet with you to discern between the 2 variants.
The 4.0's at 150-200K usually require a new crankshaft position sensor. Symptom is no spark, requires disassembly of transfer case linkage, 3 feet of extensions and a universal joint to replace. High idle at start is the idle air control valve (easy) and delays in throttle response or strange throttle behavior is the throttle position sensor (easy).
The '95+'s had body control modules (BCMs) that controlled the interior lighting, windows, etc. If you see the interior lighting and such acting funny, it's most likely the culprit ($).
Some 96-01 Cherokees and 4.0 GC's had piston skirt failures, listen for loud engine noise. If the head has 0331 stamped on it then it is likely an infamously flawed head. Most 4.0's at this age also have cracked exhaust manifolds. Most never grow bigger than a hair though and seal when the manifold heats up. Upon initial start, go under the hood and use your nose to smell for un-catalyzed exhaust. Should be a loud tick at that time also.
Plenty more, but the Jeepforum has write ups on how to fix most things.
Best of luck on your purchase.