D4 7U Oil in Clutch Housing

Look at this thread and perhaps some of these other guys will chime in. It sounds as if your tractor might have had the modifications for the rear main oil seal and now you have done away with the oil return.

http://www.acmoc.org/bb/showthread.php?18217-9U-dry-to-oil-clutch-conversion/page9

Is your crankcase breather clean so the engine does not pressurize the crankcase until the rings seat properly? .

Look at this thread and perhaps some of these other guys will chime in. It sounds as if your tractor might have had the modifications for the rear main oil seal and now you have done away with the oil return.

http://www.acmoc.org/bb/showthread.php?18217-9U-dry-to-oil-clutch-conversion/page9

Is your crankcase breather clean so the engine does not pressurize the crankcase until the rings seat properly? .

[quote="ccjersey"]Look at this thread and perhaps some of these other guys will chime in. It sounds as if your tractor might have had the modifications for the rear main oil seal and now you have done away with the oil return.

http://www.acmoc.org/bb/showthread.php?18217-9U-dry-to-oil-clutch-conversion/page9

Is your crankcase breather clean so the engine does not pressurize the crankcase until the rings seat properly? .[/quote]

The old thread was helpful--not sure I understand completely yet the oil flow path at the rear of the engine--here's what I think currently;
1) rear main oil returns to the crank case via the 3/4" hole at the top rear of the oil pan. (since my pan had no hole oil could not return--so ended up in clutch/bell housing)
2) when running an oil clutch the large oil seal on the front side of the flywheel keeps clutch housing oil from migrating to the crankcase via the bell housing and rear main seal area.
3) the 3/4" hole at bottom front of the bell house needs to be plugged for oil clutches to keep oil in the clutch area and not move to the cavity at rear of oil pan and bell housing and then into the crankcase via the hole used by the rear main seal.

My experience is that on steep slopes oil from the pan runs back into the flywheel housing and then into the clutch housing if it overflows the flywheel housing mating flange inside. This oil comes from the rear bearing escaping past the screw 'seal' but also from gaps that exist between the pan/engine and the flywheel housing mating areas back of the sump/engine. Once the oiil enters the flywheel housing, it cannot move easily back to the sump. The 1/2" drain hole originally provided seems to be there to allow any oil escaping from sump (eg. via the rear main) to drain into the bottom of the flywheel housing - not to return to the sump. In essence, on steep slopes sump oil can move into the flywheel housing - hence Cat's field mod to install a seal on the back of the flywheel.

This seal was also necessary to separate clutch oil from engine oil on optional and later fitted oil-filled clutches.

Once the seal is installed, the 3/4" hole allows oil to enter the space created behind the flywheel and to lubricate the seal. Oil flows back and forth from the sump into this space including oil that escapes past the modified screw seal on the rear crank bearing but it cannot enter the flywheel housing nor the clutch housing because the seal blocks it and the orginal 1/2" hole is also blocked.

Interestingly, talking to my neighbour he said the oil flow issues with the d4 7U's became known at the time and a few engines were lost due to oil starvation on slopes. Fitting the seal was an option but that took time and money so they simply topped up the grearbox/flywheel housing with 30wt oil until both were in harmony. He said the dry clutch continued to work just fine in oil.

You situation suggests that the sump is being pressurised such that oil is being forced into the flywheel/clutch housing regardless of seals or drain holes. I can't see why the absence of the 3/4" hole for example will make any difference. Oil should still enter the space behind the seal either from the rear crank bearing assembly or from gaps in the various castings in the flywheel housing to engine area. It would simply gather in the space until the space was full after which it should flow back. It should not be able to force past the flywheel seal unless it is being pressurised.

[quote="Inter674"]My experience is that on steep slopes oil from the pan runs back into the flywheel housing and then into the clutch housing if it overflows the flywheel housing mating flange inside. This oil comes from the rear bearing escaping past the screw 'seal' but also from gaps that exist between the pan/engine and the flywheel housing mating areas back of the sump/engine. Once the oiil enters the flywheel housing, it cannot move easily back to the sump. The 1/2" drain hole originally provided seems to be there to allow any oil escaping from sump (eg. via the rear main) to drain into the bottom of the flywheel housing - not to return to the sump. In essence, on steep slopes sump oil can move into the flywheel housing - hence Cat's field mod to install a seal on the back of the flywheel.

This seal was also necessary to separate clutch oil from engine oil on optional and later fitted oil-filled clutches.

Once the seal is installed, the 3/4" hole allows oil to enter the space created behind the flywheel and to lubricate the seal. Oil flows back and forth from the sump into this space including oil that escapes past the modified screw seal on the rear crank bearing but it cannot enter the flywheel housing nor the clutch housing because the seal blocks it and the orginal 1/2" hole is also blocked.

Interestingly, talking to my neighbour he said the oil flow issues with the d4 7U's became known at the time and a few engines were lost due to oil starvation on slopes. Fitting the seal was an option but that took time and money so they simply topped up the grearbox/flywheel housing with 30wt oil until both were in harmony. He said the dry clutch continued to work just fine in oil.

You situation suggests that the sump is being pressurised such that oil is being forced into the flywheel/clutch housing regardless of seals or drain holes. I can't see why the absence of the 3/4" hole for example will make any difference. Oil should still enter the space behind the seal either from the rear crank bearing assembly or from gaps in the various castings in the flywheel housing to engine area. It would simply gather in the space until the space was full after which it should flow back. It should not be able to force past the flywheel seal unless it is being pressurised.[/quote]

I believe it is pressurized oil because the 1/2" hole at the top rear of the pan does NOT exist on my new pan--thus engine oil is being forced into the rear bearing area and can't return to the pan. I intend to drill a 1/2" hole at the top rear of the pan,this hole--which should provide a drain path for all engine oil back to the pan. Additionally, to separate engine oil from clutch oil I'll put a freeze plug in the bottom of the flywheel housing--thus keeping the two oil systems separate. Lighter 10 wt. oil in the clutch housing and 30 wt. oil (black and dirty) in the engine. I'll fab a dip stick for the clutch housing (thru the top cover) and keep the oil level such that the flywheel runs in about 2" of oil.Thanks for your comments and thoughts.

Yes that should work. I forgot about the 1/2" hole which would as you say enable the oil to enter the flywheel housing, so blocking this hole and providing a return hole to the sump should fix the problem nicely.