advice on rod bearing replacement

I have isolated my knocking in my 4.0 auto and I'm about to go outside and replace the rod bearings. I have a good idea of what I'm up against, but I've never done it before. Anyone have any advice or tips?

If you're not lifted, disconnect the shocks and sway bar links and let the axle droop as best you can to gain clearance-- I'd look at mains and rear main seal when I was in there. You might also want to replace the oil filter adapter o-rings since you're under it getting sloppy anyway.

let me know how it goes...I might have to do this soon

Shorty said:

If you're not lifted, disconnect the shocks and sway bar links and let the axle droop as best you can to gain clearance-- I'd look at mains and rear main seal when I was in there. You might also want to replace the oil filter adapter o-rings since you're under it getting sloppy anyway.

Click to expand...

x2

I did this about a year ago on my 91. I've just got a couple of points to add.

1) Make sure you have some rubber hose to go over the threads of the rod, You definately don't want to score the crank. If you do, or it is already scored (run your fingernail over the surface to see if you feel anything), you will need to get the crank ground.
2) Make sure you plastiguage each bearing to make sure its within spec. Do this before you use any assembly lube. When I did mine a had a full set of standard size bearings and two sets each of under and over sized just in case i needed them.
3) Might as well take care of anything else while you are under there. (rear main,oil filter adapter rings, oil pump, etc)

menos said:

I did this about a year ago on my 91. I've just got a couple of points to add.

1) Make sure you have some rubber hose to go over the threads of the rod, You definately don't want to score the crank. If you do, or it is already scored (run your fingernail over the surface to see if you feel anything), you will need to get the crank ground.
2) Make sure you plastiguage each bearing to make sure its within spec. Do this before you use any assembly lube. When I did mine a had a full set of standard size bearings and two sets each of under and over sized just in case i needed them.
3) Might as well take care of anything else while you are under there. (rear main,oil filter adapter rings, oil pump, etc)

Click to expand...

X2
You may want to check the codes on the side of the block near the distributor, they sometimes put odd sized bearings in the motor. Worth a look before hand, to avoid extra trips to the parts place or having to wait for an order to come in with your motor disassembled.
I drove my motor just like a new engine for the first few hundred miles, used regular fossil oil and then changed it back to synthetic. The new bearings have to wear into the imperfections in your crank. It's been a couple of years now, everything worked out well for me.

Well I got em done they were all standard. They were pretty bad, but the journals were in good shape. It wasn't that bad of a job, it took about six hours since I never done it before. I got more dirty than I've ever been in my whole life though. I do need to do the mains. Any advice?

dfete91 said:

Well I got em done they were all standard. They were pretty bad, but the journals were in good shape. It wasn't that bad of a job, it took about six hours since I never done it before. I got more dirty than I've ever been in my whole life though. I do need to do the mains. Any advice?

Click to expand...

IMO don't. If your oil pressure is that low, buy a crank and bearing set from a wholesaler.
IMO there is less chance of satisfactory results doing the mains, without turning the crank. Turning the crank and matching the bearings isn't easy and only turns out as good as the machinist is and the selection of bearings (sizes) they have handy to achieve proper tolerances.
The main journals rarely wear flat, they get kind of cone shaped. You can see this with plasti gage, the tolerance changes along the length of the plasti gage stripe. Grooves and ridges (even microscopic), get hot and scorch the new bearings.
If your oil pressure isn't too bad and the side play in the crank isn't too bad, leave it be. 4.0's and 4.2's have a history of running a good long while with some fairly dramatic main bearing clearances.