Possible for engine oil to leak into manual transmission? (vehicle, truck, replacement)
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I had my manual transmission replaced in January. I picked the vehicle up and it was fine. Lately I have been noticing a rattle when I am below 1000 rpm only when the vehicle is warmed up. When its cold there is no noise.
I was wondering if the fluid in the transmission was low so I went out to check it today. After I removed the fill plug at the top of the transmission oil poured out. It appeared to have the coloration of motor oil and not the normal blacker color of the syncromesh manual tranny fluid.
Questions:
1) If the rear main seal was incorrectly installed during the transmission replacement would it be possible that motor oil is leaking into the manual transmission?
2) If #1 is not possible how did the mechanic fill the transmission past the full level? There is a lower "drain" plug and an upper "fill" plug. As far as I know these are the only two points oil can enter or exit the transmission.
I am wondering how the oil became "overfilled"? I was on a level surface and the truck had been sitting for at least 6 hours so it wasn't warm. I think the spec for the manual transmission fluid is 75 weight while my engine uses 5 weight. If the engine oil is mixing with the tranny fluid it can't be good.
While YMM and equipment is always helpful for a diagnosis ....
There's simply no way that the engine oil is getting into a manual transmission on your truck. If the rear main seal on the engine was leaking, the engine oil would be coming out the bottom of the bell housing.
There are many ways that a transmission could have been overfilled ... on the bench, or filled through the shifter port, or simply overfilled by pumping in too much fluid when filling into the upper fill/level plug and quickly putting the plug into the trans.
Are you sure about the "75 wt" spec lube for the trans?
While YMM and equipment is always helpful for a diagnosis ....
There's simply no way that the engine oil is getting into a manual transmission on your truck. If the rear main seal on the engine was leaking, the engine oil would be coming out the bottom of the bell housing.
There are many ways that a transmission could have been overfilled ... on the bench, or filled through the shifter port, or simply overfilled by pumping in too much fluid when filling into the upper fill/level plug and quickly putting the plug into the trans.
Are you sure about the "75 wt" spec lube for the trans?
75W-85 GM PN 12346190 is what the Valvoline PDF says.
You didn't say what model car you had, but I'd venture to say it's impossible for engine oil to leak into the transmission due to the fact that there is no direct connection from the engine block to the transmission case. There is a bellhousing with a flywheel and clutch that creates an "air gap" between the two.
This is a typical bellhousing of a RWD car. The flywheel and clutch would be here, and this would bolt to the engine block. If the rear main seal leaked, it would just leak to the ground as it wouldn't pass through the flywheel. It would be behind it
BTW refer to the owners manual for the correct fluid. Some use motor oil, some use synchromesh, some use ATF, so double check.
I have oil in my transmission plus in my air intake what is that from (96 ford winstar 3.8 motor)
What kind of oil in the transmission?
Oil in the air intake is probably from the crankcase ventilation system. It may be an indication of excessive blowby past the piston rings, causing excessive crankcase pressure.
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