Oil pump drive shaft sheared off

quicksandfarmer · Jul 24, 2012

On Sunday, after a few hours of mowing I pulled into the driveway to put the tractor away and as I shifted gears the oil light came on. I towed and pushed the tractor the rest of the way into the garage. I had to split the tractor to get the sump off (see my other thread) but with that done I have the pump out. The drive shaft is sheared off right above the rotor.

Should I be worried about the underlying cause, or should I just file it under "it happens"? I'd hate to have to go through this again.

RonMar · Jul 24, 2012

Did you find anything in the rotor or pump housing that might have jammed the rotor? I pulled a fuel oil burner out of the trash at work, that felt like the motor had locked up. When I disconnected the pump from the end of the blower shaft, I found the blower and motor rolled over and ran find. I stripped the feedpump and found some crud in the gears of the pump that had caused it to lock up solid... Could be the same thing happened to your pump... The oil filter is on the pump outlet so a lightweight piece of crap could have found it's way into the pump and locked it and sheared the shaft...

quicksandfarmer · Jul 28, 2012

I fully expected to find the entire crankshaft and camshaft, with associated parts, plus Jimmy Hoffa's fillings, in the sump, but I found nothing of the kind. The sump was completely clean, as was the pump. That's why it's a mystery to me -- the drive shaft sheared off with no apparent cause.

Bob Rooks · Jul 29, 2012

Does it appear that the gear and shaft were one piece, or was the shaft staked to the gear. Some old style gear oil pumps had the gear pinned or staked to the shaft and had known problems. Gerotor style oil pumps became the favorite of many engine manufacturers.

quicksandfarmer · Jul 29, 2012

The gear is still attached to the shaft, the shaft is in two pieces.

Bob Rooks · Jul 30, 2012

quicksandfarmer said:
The gear is still attached to the shaft, the shaft is in two pieces.

Then I assume the gear and (the broken) shaft are two separate pieces, which was my question.

Soundguy · Jul 30, 2012

no crud in the gears.. and marks in the gears like dimples in the faces?

quicksandfarmer · Jul 31, 2012

Bob Rooks said:
Then I assume the gear and (the broken) shaft are two separate pieces, which was my question.

Got it. The gear is separate from the shaft, held on with a half-moon key and a nut and lock-washer on the end of the shaft.

quicksandfarmer · Jul 31, 2012

Soundguy said:
no crud in the gears.. and marks in the gears like dimples in the faces?

No crud, no marks. Everything looks clean and fresh.

quicksandfarmer · Jul 31, 2012

Bob Rooks said:
Does it appear that the gear and shaft were one piece, or was the shaft staked to the gear. Some old style gear oil pumps had the gear pinned or staked to the shaft and had known problems. Gerotor style oil pumps became the favorite of many engine manufacturers.

(OK, read a little more closely). I guess I have the "old style" pump, the gear is separate from the shaft. It is a gerotor with four inner teeth and five outer. If they have "known problems" then I feel better about a seemingly-unexplained failure.

Thanks.