86 Cherokee engine Vibration

Hello, I have a 1986 cherokee 4X4 with a 2.8L engine, the engine vibrates as if the harmonic balancer is bad. I replaced it, yet still it vibrates. I have been told stories about this chevy engine is balenced internaly by the crankshaft. is there any common fixes for this? im starting to hear a rod/main rattle at higher rpm now. can anyone help? :screwy:

I don't like to be the bearer of bad news, but I'm surprised the Chevy mill is still running at all. If that is the Dauntless V-6 it is probably time for a complete re-build, or even better, try to swap in the 4.0L in-line 6 if you can at all. The GM V6 was not used for very long in the Cherokees, but you can probably replace it with an American Motors in-line 4.0 or 4.2 cheaper in the long run than try to fix up that old V6. It just was not a very good engine to begin with.
I'm sorry!
tb

Before you go to the extreme, check a couple things first. Cylinder compression, ignition system(are the cap,rotor,plugs, wires in good shape. Any fouling of plugs) try to adjust your carb's rich/lean jet screws to even out the rough idle. What oil presssure are you at? These are just some of the things to look at. If the compresion test is good then you might be ok, that is as long as your oilpressure is within specs.
Not sure whats involved in changing over to the 4.0, but I'm certian that most of the engine compartment items will need to be changed over. This resulting in having to buy a wrecked jeep and robbing all the parts from it. It can be done, but its no easy task.
Look at these few things first then go on from there.

Problem found! I went to replacing the rod bearings and found out that the engine had been rebuilt in 1999, and the crank had been balenced! I balenced the flex plate and the vibe went away. yet I still have a few issues. when removing the engine, unbolting the flexplate from the torque converter resulted in a tranny mess! the fluid drained from the converter. I think thats bad! I still have the rattle in the engine and my rpm is high for the speeds. 3000 rpm at 60mph!!