Intermediate Shaft Bearing wear

[Tom Oxner]

I have just disassembled my 85 930 (with 120,000 miles). The main and rod bearings look great. The intermediate shaft bearings are worn to the copper in the upper one half of both bearing shells. Since the chains pull to each side and the gears wold seem to have little up or down pressure, I am a stumped as to why the bearings would be worn in this manner. Any suggestions? Thanks.

Tom

[KTL]

Cross post this to the engine rebuilding forum. The experts will chime in that they too see this in 3.2 engines all the time.

[88911coupe]

I recently broke down my '88 3.2 and will check to see the wear patterns but I did notice some copper showing on the intermediate shaft bearings while the main and rod bearings look nearly new, even with 160k miles. I would "guess" though that possibly the bearing shells are possibly pinched a bit at the center line, resulting in inreased wear at those points. Also, maybe the chains pulling to each side effectively keeps wear down on either side...just speculation on my part though.

[Gunter]

3.2 or 3.0 or any size has the same design.
The heavy wear on the I-shaft bearings is due to the chain sprockets driving the camshafts and have to overcome the tension of the valve springs.
The I-shaft works very hard and has only 2 bearings; the crankshaft by comparison has 8 to equalize the load.
You'll also notice more wear on the teeth of the chain sprockets compared to the cam sprockets and idlers.
If you use a new chain, get new chain sprockets as well.
Do not use a new chain on old chain sprockets:

New chains without new sprockets? Read this!

[Rot 911]

Same thing on my 3.2 when I rebuilt at 130,000 miles. Rest of the bearings looked great.

[dtw]

Ditto on an 85k 2.7 I opened up a few months ago, and on an absolutely immaculate 100k 3.0 I opened up this weekend.

[Superman]

You need to also look for specks on the other bearings. Not just wear. Bearings are soft, and part of their job is to capture particles. The rear-most main bearing gets oil first. It likely has bits in it.

[Tom Oxner]

It seems that this is somewhat of a "normal" wear pattern. That provides some relief. I feared that there was something unusual (expensive) going on. Thanks for your help.

Tom