Transmission Drain Plug (Bottom)

[Stu Jackson]

In a recent post on an old subject, Complete Fuel Filtration, at http://c34.org/bbs/index.php/topic,1213.0.html
there was a bit of a discussion later on in that long thread about the use of the bottom drain plug.  I mentioned that I thought that there were dissimilar metals between the housing and plug itself, and recommended using the top plug to extract and refill the transmission fluid.

Turns out that I was wrong.  Here's the real story from Ron Hill:

Transmission Drain Plug:  I've always recommended that people let it alone if it's not leaking, as fooling around with it will surely make it leak - if not worse. The plug is made of a harder alloy than that of the  aluminum case.  If you over tighten/over torque you know which threads will strip first - not the plug!

The location of the plug is underneath where you can't see it, so you remove/replace it by feel.  It's a tough place to get to.
The Aluminum washer is a one time compression type washer - how many people are going to replace it with a new one each time they remove/reinsert the plug?  The top plug/dipstick has the same washer, but the top plug doesn't need to really be tight as it won't leak.

Then there's the location of the drain.  When the transmission is completely full (winter storage) it holds a little over a quart of fluid.  That means (in the spring) you'll need some kind of skinny container that will go
underneath to catch that quart + of fluid.  I doubt that most can catch all that fluid without a big mess.

So, all in all - As I've done for the past 16 years, I'd recommend that an owner suck out the transmission fluid from the top (just like they suck out the engine oil) and not take the chance of screwing up that transmission
drain plug.

Thanks, Ron.

Stu

[Ken]

For adding or removing oil in the transmission, I use a pump that is used for adding oil to the lower unit of an outboard engine. It fits a one quart container of transmission oil and the hose goes into the top hole in the transmission.
Ken - Trident - 1300