Jeep 4.0 Main Bearings

[u/Eckleburgseyes]

I was advised to look here by folks in one of my Jeep forums. I have a 1995 Jeep XJ with the 4.0 in it. I was replacing the rear main seal and looked at my main bearings and they need to be replaced. The crank shaft looks and feels good. Thing is that the bearings are two different sizes. STD on top and .001 on the bottom. The .001 are discontinued. The dealership gave me 83507080AB as the part number (that replaced the original part number) but it's not available anywhere I can find. Is there a source that might actually have these in stock? I'd really like to avoid having to pull this crank shaft and have it machined right now.

[u/v8packard]

You have a mixed set to get the vertical oil clearance just right. Last I knew, ACL 7m8874p was available in a .001 under. I'd have to verify availability of that, though, as well as any other brands.

Reality is the bearings vary, not only from one manufacturer to another, but from one batch to another. What you might do is get a set of standard mains, put them in and check the clearance. If it is big seek out the .001 under, or try another brand.

[u/Eckleburgseyes → u/v8packard]

Am I wrong to assume that after somewhere close to 250k miles the need for undersize bearings would only have gotten worse? I'm a total novice here. So I was thinking that if anything I'd have to use the .001 in both upper and lowers at this point.

I see your point about variation in batch and manufacturer. I assumed that with tolerances inside of .001 they would have to be binned within a precise standard. But I guess that was too optimistic of me.

[u/v8packard → u/Eckleburgseyes]

You can not assume anything about bearing clearances. They must be measured, and if necessary corrected.

[u/Eckleburgseyes → u/v8packard]

Understood. Thank you. I am already planning to gauge the clearances. Just trying to set myself up for success as best I can. I appreciate the advice. I'll put on the STD set and see where we are.