Hey guys,
Did a search and couldn't find anything on this,

My 300sd is using a lot of tranny fluid and I can't find a leak any where under the car.

I am gaining oil level in the crankcase.

Could the modulater valve diaphragm be causing this?

Any ideas ?

Thanks, Tom

It could. Pull off the vacuum line and see if it's full of fluid.

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

Yes.

All vacuum air is dumped in the crankcase.
If the transmission modulator diaphragm fails, this is a rather common issue.



.

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1985 300SD
1983 300D
1984 190D
2003 Volvo V70
2002 Honda Civic

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I'd think the good news here is that the trans fluid in the crankcase wouldn't be nearly as harmful to the engine as say coolant or some other chemical. Some even add it to engine oil deliberately to flush things out (then change the oil immediately after).

-J

It's a long journey from the transmission back to the vacuum pump through at least one orfice. How much can make that journey?

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

(It's a long journey from the transmission back to the through at least one orfice. How much can make that journey?)

About 2 qts in 150 miles!!


Tom