I've been searching a bit and can't seem to find much info on whether or not it's wise to attempt to replace your own rod bearings. Mainly, does it require special tools/skillset, such as for checking clearances and such? Or, will it make matters worse if you don't have them exactly at the right clearances, or something.
I recently bought this truck for pretty cheap, with plans of using it over the winter as I'm fixing it up, to flip in the spring. After many replacements (radiator, shocks, tires, tie rods, front driveshaft, rotors, brake lines (including making a new rear passenger, which was a real pain), plugs and wires, coil packs, fog lights, touchscreen radio, door speakers, bypassing the evap canisters, with no new codes, btw, and etc...I've now got about 4500 in it total, which is close to the average resale for 235k miles and decent condition. It has the rotted bedsides, which I'm planning on addressing as well. However, I recently damaged the driver side doors pretty good, and am thinking it's unlikely I'll even break even, especially if I replace the doors and repaint it. I'm now considering keeping her as a work truck until she croaks, which is why I'm thinking about fixing the rod knock, hopefully without a big mechanic bill.

 

You can do rod bearings with simple hand tools, and some plasti-gage. (available at any auto parts store). The bearings have a tolerance, and so long as you can get within that tolerance, you are golden. This assumes, of course, that the journal surfaces/rod ends aren't trashed..... as that would eat the new bearings right quick. While you are in there, it likely wouldn't hurt to do the mains as well. They all exist in the same environment......

 

Thank you for that info. I watched a couple videos on plastigage, and looks pretty straight forward. Is it possible (or at least not a major pain) to do this job with the motor in the truck, or better to go ahead and pull it? I'm also interested in seeing what my sludge situation is after running a few hundred miles with Marvel Mystery Oil. I can tell the oil is getting dark pretty quick, so I'm hoping it's cleaning it well, but slow enough to not clog up passages and stuff.

 

Don't know if you can do it in the truck or not.... On my 96, (4x4) I could drop the pan without lifting the motor, and everything was right there. Some of the bearings that would be right above the crossmember will likely be challenging, but, I don't think it would be impossible. But, you have a 3rd gen, and a different motor..... so, all bets are off.

 

Pardon my ignorance, but I'd like to get this fairly straight before I commit to the process. I assume I need to pull it apart and do the clearance testing before I order the new bearings, correct? Also, my initial search for parts always seems to find full sets of bearings of the same thickness. If one rod is worn enough to need a larger bearing, do I need to order another set for it, or does that mean it requires a different fix? I appreciate your help in this.

 

This is WHY we are here. To answer questions like this.

You could measure clearances before ordering bearings. But, if you need undersize bearings, (oversize?? I keep confusing that aspect of it.) you have bigger fish to fry. Basically, if stock bearings are out of spec, the crank needs to come and, get resized/polished, as do the rods. So, pretty much a rebuild. Given that you have a couple knocking already.... I would not be at all surprised to see a couple crank journals that were scored, and a couple rods that the ends were no longer round. Depends on how long, and how loud, it has been knocking. Some engines will run forever like that. Some blow up the next day. How is your oil pressure, engine fully warmed up, at idle?

 

I've never checked it with an analog gauge, but the one in the dash always shows it being within a normal range. And the truck runs strong. I occasionally (once or twice a week) give her a full throttle 0-70, up to 5500 rpm shift point, and it never sounds/acts out of sorts. I reckon that's probably not overly wise on a 235k motor with a rod knocking, but what's a redneck with a hemi gonna do, right?

 

LOLOL.

I understand that one.

If oil pressure is good, chances are, stock size bearings will work. The question becomes about the one that is already knocking...... That one may give ya trouble, and changing the bearings may not solve it.