300 TD wont shift into 4th
 

my 300 TD has about 380,000 miles. It goes into 2nd and third fine, about 5 mph later than the marks on the spedometer, no slipage, but sometimes the shifts are delayed, like 3rd happens closer to 50 MPH.... Never 4th gear.

Ive gone as much as 80 MPH and RPMS only climb 3500, 4000...

Incidentally, when I turn the car off theres a noise on the driver side, like air escaping that goes away in a minute, I figure is a vacume leak...

would that be the cause, or what other possibilities?

I just bought the car and for me its always been this way. Should I just figure "bad tranny" and resell the car?

Thanks

mikeptag,

With those miles on the counter you should check out your vacuum system,
specially the tubes and rubber connections to the tranny.
But in the first place verify the ATF oillevel in it. Than take out every "restrictor" in the vacuum system. These are the small plastic tubes with a restricted opening in it between two rubber hoses or elbows. If you can't see light through it, clean it with one "hair" of a steelwire brush ( handy to clean the orifices of the windscreenwashers to! ).
Anyway, you should do a search on this forum : there is so mutch written
about auto trannies and the vacuum system here.
Good luck8

Danny