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bearings/ .001-STD?

A

arhiney

NAXJA Forum User
Location
Fort Leonard Wood, Mo
I just pulled the rod bearings out of my 95 xj 4.0. They were definetly the cause of the knocking I've been hearing. My question is: Am I supposed to have a mix of STD and .001 bearings? The top bearing has .001 stamped on the back and the bottom has STD stamped. Is this normal? Should I replace them with the same mix? Will the plastiguage be the deciding factor? Does this mean the bearings have been replaced before? What should I start with? Any help would be appreciated. TIA.

Adam
 
That is a standard procedure and it is discussed in the FSM. However, I believe it is for field service only and not done that way from the factory, so it probably means either that your bearings have been replaced previously, or perhaps when new it had low oil pressure and the dealer did that to tighten things up a smidge.
 
Eagle,
I was hoping you would be here tonite. Should I replace the same mix? I ordered STD bearings today before I tore apart the engine. Do I need to order .001 also? Should I put in the standard bearings and then plastigauge and go from there?
 
I forgot to mention that my oil pressure never dropped. I just had a knocking sound. What else should I be doing while I have the pan off? Already plan on the rear main and Main bearings. Kinda new at this internal stuff. Any suggestions would be appreciated.

oil pressure was at about 37 (idle) and 55 at running speed and at times above 60
 
If it was me I would have the crank polished to a standard size.Look into getting a crank kit,these have a new(used) crank and the correct bearings all together,might be faster than waiting for the machine shop.
Wayne
 
If it were mine, I would replace with .001 undersize all the way around, and then check with plasti-gage. You have probably polished another .0005 off the journals in the course of driving it.

To answer your original question, plasti-gage should indeed be the determining factor.
 
ok, got it. thanks. next question is: Where to buy bearings and what brand? Autozone carries Hi-Tech and Clevite but thier sizes show .010, .020 and .030 "oversize". I know the back of my bearing says .001. Is there oversize and undersize? Need to order soon so I can get back on the road. TIA

Adam
 
Pistons and rings are "over"sized -- bearings (rods and mains) are standard or "under"sized. Nobody has a crank that's bigger than standard.

The aftermarket sources are going to have the .010 and .020 undersizes because when a machine shop has to grind a crank, they go to one of those as the "standard" undersizes. (Just as pistons come in standard and .010, .020, and .030 over). The .001 and .002 undersize shells are dealer only, as far as I know.
 
I was hoping to avoid dealing with the stealership. I haven't been able to find .001 anywhere online so maybe that will be my only choice. Thanks again. Iguess I will have to wait until Mon to call the dealership.

Eagle,

You know Fort Leaonard Wood and how far out in the woods I am. Finding parts is hard and usually have to be ordered. What are some good online sources?
 
http://www.mopar-parts-dealer.com/parts.htm

Or call my dealer, Bradshaw Jeep. 860-274-8834, Ext 3. If possible, talk to Todd or Chris. Todd is the Jeep parts guru. Often not there on Mondays because he works the counter on most Saturdays. I'm pretty sure he can get what you need and ship it to you, and there's a chance he can work with you a bit on price.
 
Replaced all the bearings with STD and they all plastigaged at .0015. Changed the rear main and buttoned it up today. Started it up and the knock was gone (for a little while). The knock is still there ever so slightly. Maybe I have super hearing or should have gone with the .001s all the way around as Eagle suggested. It is ALOT better though. I did notice however that I am missing two of three motor mount bolts on the passenger side. Tried to replace but the original bolts are broke off in the block. Any suggestions on that. Also, could I be getting a knocking sound from the missing motor mount bolts? Like I said it is very slight.
 
In my experience is always fine to replace rod and main bearings with .001 under on a crank journal with some miles. The fact the factory or dealer had used .001 on one half was a pretty major indication it needed to go back to at the very least the same arangement with the new bearings. Plastigauge is really not that good of an indicator and should not be totally relied upon. If you ever have an engine down and apart and have the actual mearsuring tools you will be able to see how bad the variation of measurement plastigauge can read. The best engine builders hate plastigauge for it's innacuracies.

I have done 'patches' on Chev small block cranks that had significant wear using .001 and .002 under bearings (and new/better oil pumps) lots of times. Is amazing how much this can help and have gotten an additional 75k to 100k miles of additional use from the engines in the past!!
 
In the KC area, I picked up some .001 bearings from CarQuest. They had .001 and .002 available IIRC. I believe NAPA said they could get the .001's, but didn't have them in stock.
 
Should I replace the bearings with .001 right away or can I wait atleast until my next oil change (maybe my neck will be ready by then also). What are the chances of reusing the one piece rubber oil pan gasket? It will be alot easier the second time (dropping the pan). Can't say that I had alot of fun. How can I get the broken motor mount bolts out of my engine block? Probably wouldn't hurt to have more than one bolt holding the passenger side of the engine in. ha ha gotta love it
 
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