Just bought an XJ today, the one I mentioned in the other thread I started. We checked under it and the frame looked straight. We honestly couldn't find any evidence of the accident it was in. Offered $400 for it, and the PO took it. We took it to my brothers workplace up the road and used ramps and checked the torque converter bolts, but unfortunately none were loose, so now we're not exactly sure where the knock is coming from.

Here's a picture...


I'm not positive, but it looks like it's got the Chrysler 8.25 axle in back, and based on the shift pattern, it appears to have the Selec-Trac and the NP242 transfer case. Is this one pretty good? Is one preferred over one of the others?

We went ahead and changed the oil in it to see if it made any difference, and it didn't, still knocking and rattling away. It seems to go away as oil pressure increases, because while cruising down the road it sounds and runs fine. We're thinking that since the truck has 194k miles on it, it may not be easily fixable, or really even worth fixing, so I've started looking into replacement engines. Anyway, we made a movie of the noises, so if anyone has any input, I'd appreciate it.

 

Multiple lifters collapsing/losing their prime causing excessive clearance between the lifter and pushrod?

They might pump up at higher oil pressures.

Is the fan striking the shroud or radiator anywhere?

 

That was one of the theories we had.

Nope, checked that. It seems like it needs a new fan clutch, but it seems to be fine otherwise.

 

I know you checked the torque converter bolts, but did you check the flexplate for cracks. Mine developed a slight tick last year that slowly turned into a symphony of hammers in the lower end. The knock went away under accelleration because it locked the breakage in place. I took it to 2 shops and both times I was told that they would not even waste the time to tear into it. "That motor is shot" is what I heard both times. My brother suggested checking the flexplate because his did the same thing. I pulled the inspection cover and saw very small cracks spidering out from the center. Got a used flexplate from the jy and bought a trans jack, pulled the trans and was shocked at what I found complete and total seperation around the bolts to the crank. $15 for a flexplate, $130 for a trans jack, 8 hours of profanity in the driveway, and now no more knock.

 

Checked Compression yet?

 

We considered that, and may give it a look this coming weekend.

Not yet. We did notice some little metal shavings came out with the oil when we drained it. Definitely thinking that's not a good sign...

 

Rod bearing. Get a mechanics stethoscope or a long pry bar or screwdriver and start listening. Put it on the block and valve cover and all over, when the noise gets louder then your getting closer....

 

One of the most annoying things that happens at the shop i work at is the other "techs" will listen to something like this and automatically say they dont want to work on it. We had a volkswagan come in with a broken timing belt and just becuase the computer said it was an interfearence motor they wouldnt touch it. Did they even think about getting out a compression or leakdown tester out? NO.