Hello all,

I have a question regarding flywheel mounting on my gen3 5.3 Silverado. I am in the process of piecing back together my truck after replacing the rear main seal. During the removal process I did not mark the flex plate / crankshaft upon removing and was wondering if it mattered if the reinstatement position would effect the balance. There are 7 holes in plate in circular pattern with only 6 bolts , the additional hole in both the crank and plate are not matched up in the motor I have from a different project (I assumed the extra hole was an alignment hole but after looking at the other motor it disregarded that thought) I added a photo of a plate for reference like mine described (a YouTube screenshot , not my actual project). Doing this on ground without a lift so not wanting to have to pull apart again if vibration due to unbalancing. TIA

the extra (alignment hole)? I circled in red. This guy unlike me marked his plate so hopefully you all can give me some guidance. May be overthinking it but as much fun as this rear main replacement was I don’t want to have to separate tranny again

 

My instinct is to say that it's for alignment or visibility of something else. Because to remove that much material for sake of balancing? It doesn't pass the sniff test for me. Unless you see something (presumably directly opposite) of the side where the hole is that might account for an addition of weight to justify that hole's removal of weight, I would think it's an unnecessary step to concern yourself with where that aligns.

But I did find this video: Now, it shows the install for a 350 rather than a 5.3, but the hole is indeed there in the same pattern. So if your engine doesn't have a spot for that dowel that's featured in the video, I'd say we're looking at a feature that crosses over. So maybe the same flywheel is used on 5.3's AND 5.7's, but only the 5.7 has an indexing dowel for "correct" installation. It could be you simply don't need to worry about it.

Now I found another video of a 5.3 rebuild. This guy's 5.3 crankshaft appears to show a hole for lining up that hole in the flexplate: If you go to 7:50 you'll be able to see the hole in the end of the crankshaft. Then at 9:02 he holds up the flexplate and the hole in question exists on it as well. For me, this gives credence to my initial speculation about cross-compatibility for engines, but also seems to very clearly indicate alignment. And pictures I'm finding of crankshafts for 99-06 seem to have this hole for alignment purposes. Does your crank really not have that hole?

 

Indeed helpful information! I don’t have a dowel pin on mine! I’ll be glad to get it all back together and hope that I fixed the leaking rear main nevertheless I knew I had to be over complicating it but wanted some other thoughts/ opinions. Thanks !