Common issues?
 

Sorry if this has been asked somewhere else. The search did not produce good results for me.

I'm going to be looking to buy a 97 Grand Cherokee 4.0 4x4. What are the common problems I should be looking for?

Welcome to CF!

3 things come to mind. Undercarriage rust if it's from the rust belt, especially around the control arm attachment points. Bad color or smell from the transmission fluid, and a good transfer case. I'd drive it to check for transmission feel and solid shift points.

The ZJs came with 2 different t/cases, the NP249 full time 4wd (Quadratrac) or the NP242 Selectrac which gives you a 2wd option. The 242 is pretty much trouble free, but the 249 is known for bad viscous clutches which cause the front axle to skip or hop in tight turns. If the rest of the jeep is perfect, you can fix or swap the t/case pretty easily, but keep that in mind when buying it. Replacing a viscous clutch is expensive and requires taking it completely apart.

The rest are basic maintenance items like wheel bearings, ball joints, u-joints, brakes, and the cooling system. Pull off the oil filler cap and look down it with a strong light to see if there's any sludge buildup in the valve area. If you're not familiar with jeeps, the 4.0 does "rattle" a bit at idle, a little valve clatter, but any other deep sounding noises are suspect.

Good luck! I hope you find a good one. If it's been lifted, take someone with you that knows jeeps and can tell you if it's been done properly.

@dave1123, super helpful. Thanks!

You're welcome. I made a big mistake with my first jeep. I didn't do the research and bought a POS 97 ZJ with a bad transmission and lots of rust underneath. I got it cheap but wound up putting $3000 into it the first year! The second year, after welding 100 lbs of metal into it to fix torn out rear lower control arms, it still wouldn't pass inspection. Water under the bridge. I never had problems with either the 4.0 or the 242. The rear axle is a long story.

Dave what kind of issues did you have with the rear axle?

Just guessing but would say a D35.

Okay, here's the dirty story with the rear axle. Yes Fred, it's a Turdyfive! When it was in the shop getting the trans rebuilt, the guy asked me if I wanted the leaking pinion seal replaced. I said "Yes, if you know what you're doing." He took offense at that.

Immediately after picking the jeep up, I hit the highway for Binghampton to see my brother, about 1.5 hours away. This is summer, 65 mph, all the windows down, radio on. After about 30 minutes, I'd had enough radio and turned it off, at which time I heard a whining from the rear axle. As I was slowing down for an exit ramp, the rear axle EXPLODED! I got out and looked at it. It was smoking with a hole in the rear cover and gear oil everywhere. I removed the rear shaft, put my 242 in partime 4wd, and drove it home slowly on secondary roads. The rear was completely silent because the pinion bearings had blown apart enough for the pinion to be completely disengaged from the ring gear.

Furious, I went back to the shop in the morning and *****ed a fit! They had preloaded the bearings too tight causing the failure. They agreed to put a new set of gears and bearings in it, but wanted me to pay labor. I said no and would contact my lawyer, after which they agreed to pay for all of it. After a week, the axle started whining slightly so I went back again only to find them out of business! This was a franchise of a national known company, not some fly-by-night shop. I contacted the home office only to be told to take it up with the shop owner. I researched him but he wouldn't answer the phone. I sent a registered letter to him and got no response. I talked to my lawyer and was told to submit a claim to small claims court but was advised if I lost the case, I would have to pay court costs.

In the end, that axle whined for the next 2 years, getting louder, until I sold the jeep. This is why it is ABSOLUTELY IMPERATIVE that you know what you're doing when working on a rear differential.