911 oil pump gears & sliding on their shafts (or not)

[stownsen914]

I've heard that it's important that the gears in a 911 oil pump slide easily on their shafts (the non-fixed ones of course), that this floating keeps the gears from wearing the ends of the housing during operation. Is this true?

If so, is it just as important for the driven ones held in place by the keyway, to also slide freely?

I have a pump in which one of the floating gears held by a key, doesn't slide freely. I'm wondering how big a deal that is, and what if anything I can do to address.

[BURN-BROS]

Both drive and driven need to slide freely. I have seen galling on the drive side that prevents axial movement. This can cause excessive wear between the housing and the face of the gear. FWIW, I have never seen issues with galling on the driven gears and shaft.

[stownsen914]

Thank you Aaron. I’d read your comments on this topic in another post and hoped you’d respond. I’m going to carefully press the one sticky gear off and see how stuck it is.

In your experience, is it possible to polish the affected areas to rehab the pump?

[dannobee]

Yes, you can polish the gear/shaft/keyway to get it to move freely.

It shouldn't require a press (unless you mean a small arbor press). It's likely just a little burr somewhere.

[BURN-BROS]

Originally Posted by stownsen914

Thank you Aaron. I’d read your comments on this topic in another post and hoped you’d respond. I’m going to carefully press the one sticky gear off and see how stuck it is.

In your experience, is it possible to polish the affected areas to rehab the pump?

Just enough to remove any high spots the galling may have caused. Also debur the key way. Slide the gears on and verify they do not bind. .

[stownsen914]

Thank you gentlemen

[stownsen914]

OK, so a light pressing was needed to remove one of the key/fixed scavenge gears. The shaft and gear had a small area of imperfection - galling, spalling, not sure. But it cleaned up nicely some 400 grit followed by polishing with jewelry polishing compound on a cloth wheel bit on a dremel. Gears slide nicely now.

Two additional questions ...
1. I see some light scoring of the center plate on the scavenge side where the gears spin (see pic below). The ends of the scavenge gears also feel slightly rough when I run my finger nail over them. It is advisable do figure 8s on 400 grit on a glass surface for the center plate and the ends of the two scavenge gears to clean this up a bit?
2. The cast iron pump body shows what looks like light polishing near the end where it mounts to the pump plate (see second pic below).I can't feel it, I can only see it. I also see "polishing" in the matching spot on the scavenge gear that sits near the polished area of the pump body. Measured all the gears and they are 1.412-1.413" diameter. The "polished" area of the gear is 1.412". Also measured the shafts and the "bearing" areaa of the pump housing looking for wear or ovality. The shafts all seem to be .549" and the bearing areas .550". Is the "polishing" concerning here?

[stownsen914]

Bumping for input on the last post

[BURN-BROS]

Sorry, missed this post. That scuffing looks to be about average for a pump with some miles on it. Make sure there are no burrs on the side plate and gears and reassemble. Check that it freely spins with minimal effort and put it into service.