Thanks Gary, but if the transmission is venting properly why would there be
pressure building up? Is there any way to determine if transmission is
overheating? Monitor the temperature somehow? I plan to replace the seal
and then keep an eye out for any leakage but if the transmission needs a
rebuild I'd prefer to do it sooner than later.

-Mark

On Wed, Jul 27, 2016 at 2:13 PM, gary hradek <hradek@yahoo.com> wrote:

>  Mark,
>         I have the same problem with the oil leaking from selector shaft
> seal.   I think this is just a good indicter that you have pressure
> building up in the transmission and fixing the seal will be a waste of
> time.   The time to fix it would be when you are getting the clutch done or
> some other big job when you have to pull the engine.   What happened to me
> is the end shaft axel seal popped off and oil leaked into the cv boot.
>  The selector shaft seal stopped leaking during this time.   Now that I
> fixed the axel seal the selector seal is leaking again.   My thought is
> that with age and wear the bearings are a bit loose and the differential
> produces more heat so that the oil pressure is higher than it used to be.
>  As long as you keep on top of the oil level you can keep driving but you
> may want to stick to 55 mph when you can.   You may want to check your axel
> boots for oil now and then.  Good luck, Gary
>
>  ----------------------------------------------------------------------
>
>  Date:    Tue, 26 Jul 2016 07:01:47 -0700
>  From:    Mark McCulley <markmcculley@GMAIL.COM>
>  Subject: Re: replacing transmission selector shaft seal
>
>  Thanks Dennis. I'll check the fluid level and vent tube.
>  There's no reason
>  I can think of that the transmissions would overheat, still
>  have the stock
>  2.1L and don't pull a trailer. I did switch the type of oil
>  I use a few
>  years back, 3 years ago I switched from Redline to Delvac
>  and then a year
>  later I switched back to Redline when I installed a
>  driveshaft decoupler.
>  Both oils are synthetic 75W90. The transmission has just
>  under 200K total
>  miles, 80K since rebuild (I don't know if seal was replaced
>  then or not).
>
>  -Mark
>
>  On Mon, Jul 25, 2016 at 7:08 PM, Dennis Haynes <d23haynes57@hotmail.com>
>  wrote:
>
>  > Yes this seal is easy to replace. However its leaking
>  is usually a symptom
>  > of something else going on. There is also an
>  insert-bushing behind it that
>  > may be cracked. Make sure the transmission is not
>  overfilled and that the
>  > vent tube is not kinked or otherwise clogged. This seal
>  never sees enough
>  > action that it should wear out. For it to go bad is a
>  sign the transmission
>  > has been over heating.
>  >
>  > Dennis
>  >
>  >
>