rod/main bearing replacement without pulling engine?

Hello All,

I am new to the xj world and have recently purchased a 95 cherokee with the 4.0 HO. The engine has 122,000 miles on it and runs great except for a knocking sound from the rear bottom of my engine. I have read other posts about the same problem and the advice was to drop the oil pan and replace the rod bearings. Would it be wise to also replace the main bearings at the same time? Would I need any special tools? What type of replacement bearings are best? What seals and gaskets would I need to get? I'm cheap and want to do everything myself. It's alot of questions I know. I would just like to save myself the expense of having the whole engine rebuilt or buying a re-manufactured engine. I would appreciate any comments or suggestions. Even better would be a step by step guide or a link to find one.

Thanks
Adam

The best advice I can give is to get a factory service manual. Mine says that you don't have to pull the motor to replace the bearings but it is for a different year ... get one for your '95. Mine also lists that the only special tool needed is a homemade bent-up cotter pin gizmo and a popsicle stick (no joke). Get a FSM.

The rod bearins usually go before the mains. Clearly, once the work of dropping the pan has been done it's a good idea to replace the mains while you're in there, but it may not be necessary.

BUT WAIT

122,000 miles is NOTHING on a 4.0L engine, and the problem may not be rod bearings. I assume this is an automatic? Sometimes the bolts holding the torque converter to the flex plate ("flywheel") get loose, and the resulting sound may be mistaken for a rod knock. It's also not uncommon for the flex plate itself to develop a circular crack around the hub. I recently picked up an '88 Laredo for an ex-girl friend. Kid who had it had already done bearings to get rid of the knock and it still knocked, so they decided it needed an engine and his father made him unload it. Flex plate was so badly cracked I'm amaxed it hadn't let go completely.

The flex plate can be changed without pulling the engine. Disconnect everything and slide the tranny and torque convter back, then remove and replace converter and button it all up. I bought one of those $49 Harbor Freight transmission jacks, and it was adequate for the job.

Eagle,

You're right to assume that it is an automatic. That's something I will have to look into. I'm still pretty sure the knock is coming from the engine, as I have spent alot of time under the Jeep trying to pin-point the knock. It seems to be coming from just forward of the drain plug. Maybe the #6 cylinder? Is there an easy way to check the flex plate and torqe converter? Sounds like it might be easier to do the bearings first. Also, is there any difference in bearings between the High Output engine and the regular 4.0? I really appreciate your help and time.

Thanks
Adam

You can check both by removing the inspection cover from the bottom of the bell housing. If it's loose bolts on the torque converter, that's where you'll tighten them from.

Yes, I would agree that it's easier to replace the bearings than it is to replace the flex plate. However, replacing the bearings is enough of a job that it would be a shame to go through the effort only to find (as the seller of the one I have did) that you haven't addressed the problem. It's far better to find out what the problem is and fix that than it is to just start throwing parts at it.

Aside from the labor, in addition to the cost of bearings the one-piece pan gasket costs about 50 clams. Why spend money unless you've determined that bearings are really the problem?

i also had that noise coming from the rear of my 4.0 at one time. i dropped the pan and checked eyerything which turned out to be a waste of time. so i then took my inspection cover off to find 3 of the 4 bolts two turns backed out. it solved that problem and cost nothing but time. my 4.0 has 197,000 on it with a aw-4 that are still stock. its worth a look to check those bolts out

I really appreciate the help Eagle and Mark. I know what I will be doing this weekend. I hope it is loose bolts. Thanks again.

Adam

Let us know.

And give my regards to FLW -- I did Basic and AIT there many years ago. (Frostbite 3 times, pneumonia twice -- all within 16 weeks!)