D8K pushing engine oil into transmission

Under heavy load our 1977 D8K is pushing engine oil into the transmission. It is coming out of the vent on the transmission once it gets too full, and it seems to have a power loss when that happens. Should we assume that it is a rear engine seal or are there any other things to look for before doing that enormous job? Thanks in advance.

Oh and its not plugged breathers.

Change the seal in the transmisson pump.
Bob

The common cause for this issue is found in 2 areas, the 1 is as Bob has suggested and is not to hard to fix, people have brought up the wear that happens within the drive splines that the transmission pump fits into, with suggestions of grinding the pump shaft, I find the best fix is to whip out the gear from the pto drive and turn it end over so you get a new lick of the lolly, the other cause of E/Oil getting into the trans is through the back case high up, 2 little bolts come loose and let oil work its way into the case, the rear main seal is never any trouble as its a steel piston ring style enclosure that is good at what it does, with the transmission pump being the easiest target to tackle its worth checking your engine mounting right near it, a good clue if its failed is the pipe to the magnet screen is near resting on the frame, the oil seal in the trans pump looks to be fitted back to front to how you would expect.

good luck tctractors

Check the Crank Thrust too... Worn thrusts could compound this?

Performance test the engine first, including Blow By, a workout engine with high crankcase pressure will blow oil into the trans big time. Also a flooded flywheel/converter housing will bog the engine down.
Later Bob

The 342 engine holds around 7 1/2 imperial gallons (near 10 U.S.) so if this engine is pushing out enough oil in a day to flood the flyweel case a rod is going to soon see daylight, a driver style blow by test is done by un-screwing the Oil filler cap at low idle, if it comes off its last turn like a pop gun the innards are knackered, a more fancy test is trying to top up the engine oil with the engine on low idle, if you struggle to pour the oil in with it suddenly blasting you with a free lube job its the same tale worn out (but still usable) just how much oil is the motor poking in to the transmission?? the more common route is transmission oil into the engine.
This last week I have been tarting up a knacker (D8 that is) this tractor was pushing well with just the odd moment of trans' temp' panic that seemed to sort its self some how, anyhow I whipped out the torque to find it total scrap, a bit of transmission gear carrier washer was also found, well there is 42 of them but its not a good omen, so I sucked out the gearbox and tipped its innards onto the bench and boy what a mess, the shout to strip it was in the nick of time as the costly chunks are still fit to be re-used with just the gear shafts and bearings plus the forward an 2nd speed gear ring needing replacement, the clutch discs will all be replaced in the usual U.K. style out of the Tea Chest of old plates on the "Healing Bench" ready for the next 10'000 hrs of hammer.

tctractors

I had a reacent problem with trans oil getting into the engine so tried the usual easy fix things as new seal.still did it.I replaced the seal again thinking I had it back to front?.still did it.Then I put a brand new pump in.Stll did it.......Then I called the professional in.He has removed the pto casing to find worn gears which was clearly putting pressure on the pump shaft to bounce around abit.
My 25 years of D8's transferring oil has allways been sucking it out of the tranny and into the engine.not the way yours is going.
Are you sure it's engine oil going into the trans? and how much oil are you putting into the engine?
If the torque was shot more tranny oil would hold up in the torque and not flood the trans casing I assume?
I also guess that if the oil in the transmission was so full that it was pumping out the vents or steering clutch casings the torque would still work well enough and not loose power as you say yours does.
My lay mans gut feeling is that your torque is coming out and your pto housing needs to see some day light.

Thanks guys. We will dig into it further now that we have some solid info to use. Yes it is engine oil into the tranny for sure