620 loosing engine oil to rearend

matthies · Feb 1, 2015

A guy had me look at his 620, he replaced the seal a while back and he still is loosing oil. He had the tractor torn down to the seal housing. Before I removed the housing I checked up and down movement of the crankshaft, .008 in. Seemed a little loose to me but don't have a book on a 620 to know the right amount, thinking more like .004-6. The endplay wasn't excessive, but will check once together. The main bearing looked good. Will have to find a micrometer and measure the crankshaft. Any other thoughts? thanks chris

BushogPapa · Feb 1, 2015

If he did not remove the Main Bearing casting (Quil), how would he know what that Main bearing looks like..?

I replaced the Rt Main in my 630 and I can tell you..0.005" is the Minimum clearance..it is a 4" diameter Journal....
The OIL to the Main (and Rod) passes through a connection between the engine Block and the Bearing Quil, with a Stupid "O-Ring (JD calls a "Gasket") that can (and often does) SWELL and close the oil passage to the Main/Rod Bearing..
My Rt Main went out because of this "Gasket"..
I added a short piece of Brass threaded Tube from the engine oil supply gallery, extending out enough to Prevent the "Gasket (O-Ring)" from ever swelling out and blocking the oil passage..
Your choice, but I would sure have a look at that..!
The Rt. Main Bearing Seal is usually where oil gets into the 1st Red and into the Trans and that is usually because the Main is going out from oil starvation...
My 630 had 0.076" Bearing clearance and never made any noise to indicate any problem..I just had engine oil getting into the Trans..
Hope this helps ...

Ron.

620 loosing engine oil to rearend

matthies

Well-known Member

BushogPapa

Well-known Member

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