Connecting rod bearings and main bearings replacement

Tiny
JMANN979
  • MEMBER
  • 2003 DODGE RAM
  • 4.7L
  • V8
  • 2WD
  • AUTOMATIC
  • 243,539 MILES
I have been losing of my oil pressure whenever I come to a complete stop. So I changed my oil pressure switch and that didn't help. Then I dropped my oil pan to clear my pick up tube which had old existing parts from me bad timing chain guide. So I cleared that out of the way put it back together, still had no pressure. When I drained my oil I had a copper sheen in my oil, I'm guessing from my bearings. But nothing magnetic in my oil at all. I do have a very slight new knocking sound on the bottom that I really haven't noticed before but it's not too bad at the moment. I want to change out my connecting rod bearings and my main crank bearings. What is the best way to decide on the size of bearings to go back with?
Thursday, March 19th, 2020 AT 8:45 AM

9 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
Good afternoon,

You will need the numbers off the back of the bearings for the correct ones.

Then when you are installing, you will need to plastic gauge each bearing for the proper clearance. You should have about.0015 clearance.

If there is any damage to the crank, the crankshaft will have to be replaced.

Roy
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Thursday, March 19th, 2020 AT 8:58 AM
Tiny
JMANN979
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Now. I'm needing to do all of this with the engine still in the truck. I'm sure the connection rod bearings are do able because I can remove the caps one by one as needed. But the bedplate has to be removed in order for me to replace the main bearings. I dont know if you have ever worked on one while still on the frame or know of anyone who has tried. This is my daily driver and I'm trying to do this with in a couple days while I'm off work.
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Wednesday, March 25th, 2020 AT 1:40 PM
Tiny
ASEMASTER6371
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Did you drop a cap and check for any damage to the crank?

I would try jacking up the engine off its mounts as high as you can get it.

Roy
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Wednesday, March 25th, 2020 AT 1:53 PM
Tiny
JMANN979
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I haven't opened it back up yet. I'm still trying to make sure I know what I'm doing before I start tearing it apart.
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Wednesday, March 25th, 2020 AT 3:11 PM
Tiny
ASEMASTER6371
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I hate to say this, but it would be easier to remove the engine and put it on an engine stand and do the bearings. Then if you do have crank damage, you can replace it right there.

Roy
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Wednesday, March 25th, 2020 AT 3:21 PM
Tiny
JMANN979
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Okay, so I pulled it all apart and replaced the connecting rod bearings which were stamped std; so that's what I went back with. No damage to the crank. How do I find out what size these main bearings are?
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Monday, March 30th, 2020 AT 1:37 PM
Tiny
ASEMASTER6371
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The same way bu looking on the back of the shells. They should be stamped std, -.010 and so on.

Did you plastic gauge the rod bearings to be sure of the clearance?

Roy
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Monday, March 30th, 2020 AT 1:42 PM
Tiny
JMANN979
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Yes the clearance was between. 025 and.038mm on the plastic gauge package. On the back of the old main bearing is stamped, A-500, 2 03 on one side of all the bearings and then on the other side of the bottom it's B596on all of them and the on the upper its C434. It would send an image but it wont let me.
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Monday, March 30th, 2020 AT 1:51 PM
Tiny
ASEMASTER6371
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Okay, you will need to contact a parts store or even the dealer and have them decode those numbers.

Since there was nothing showing under or over, I would assume they are standard as well.

Roy
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Monday, March 30th, 2020 AT 1:58 PM

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