I'm going to be changing out my tranny fluid and filter tomorrow and I've done a bit of research which says it's not possible to get all the fluid out without removing some circulation lines and running the engine till the fluid starts running clean. I'm not going to bother doing that, I'm just gonna change the fluid to correct levels, drive it normally for a week or so then change the fluid again.

My question is this: is it a terrible idea to re-use an otherwise brand new gasket that has been used for a week or so?

 

Depends on what is made out of,Ford uses a reusable rubber gasket but they also use a cork gasket and that can't be reused.

 

IMO, that should be fine to do, reuse gasket.

I like cork better than rubber in applications where you don't need to remove them all the time.
Over time cork gaskets will swell as they absorb fluid from the "wet" side, but they dry out on the "dry" side so after a few years they would usually break or be too brittle to reuse.
That won't happen in a week or a month.
The swelling over time prevents leaks from starting.

If you know you will be removing a gasket frequently, say adjusting solid lifter rockers monthly or........??
Then use rubber because it can be reused many times, but it can also leak if not re-torqued now and then

Cork long term
Rubber short term

Just my opinion


And as a heads up, tranny pans, like valve covers, are usually stamped steel, they are made to be torqued down once, the torque bends the steel a bit at the bolt holes to distribute pressure between the holes, they are designed that way.
You should straighten out the metal around the holes before re-installing it, this will give you the same gasket pressure that hopefully has been leak free since it was originally installed.

 

I changed the trans fluid and filter on my 2006 Mazda B4000 a few weeks ago.

There is no drain plug so it was quite messy. I also have a hoist which makes this job much easier and I still made a mess. I did plan on drilling a hole in the pan after I had it off so I could weld in a bung with my tig welder but I was out of argon gas. Since it was a Saturday I just put it back together and I'll do this next time.

You are right there is no way to get out all of the fluid because the torque converter holds a good bit of it. If you change the fluid in regular intervals this is not a problem. Personally I normally change mine every 20,000 - 25,000 miles but then again I rarely drive this truck so it only has 26,000 on it and it is 10 years old.

If you replace your OEM gasket with a rubber style one you may be able to re-use it. Some of the OEM ones are rubber with small metal spacers where the fasteners go. This is great because it won't squeeze out when you torque it down. Don't torque these 2 tight, use a small 1/4" drive hand ratchet removing and tightening. I think the Ford tech site spec was 16 ft-lbs. (but I can't remember)

I just had a 2001 Cadillac Deville on my hoist that I needed to remove the valve-body of the transmission to do some work to it. When I did this job I actually reused the factory rubberish/plastic gasket and it worked good (no leaks)

 

Thanks for the advice, guys. The filter kit I got was a Fram kit, so I assume it would most likely have a rubber gasket, though I haven't checked. I didn't get around to doing the fluid change today, so hopefully tomorrow if it isn't raining.

It's gonna be fun laying on frozen concrete for a few hours!

 

It's super easy to disconnect the return line and drain/refill. In fact it is more time consuming to remove the pan/gasket and filter than it is to do the disconnect of the line. If you are going through the trouble of changing the filter and empting the pan of fluid, take the 2 minutes to disconnect the return line and put it in a bucket. Turn the truck on, drain 3 qts. Shut truck off, and fill with 3 qts in the dipstick tube. Do this until the fluid is cherry red. I believe I used 2 gallons of fluid. Then drive around and top off after 30 minutes once you figure out what your fluid level is at once it's at temp.

The whole idea of dropping the pan to drain 3-4qts then fill it back up and drive for a week only to do this whole process again seems so dumb to me and a bad way of spending one's time. Instead of changing out the fluid to say 90% new, you end up mixing your new fluid you just dumped in with old fluid only to continue to do that for the next time. Pretty much diluting the new stuff you are putting in twice, instead of getting most of the old out in one swoop and putting the new stuff in and not having to change it until 30k miles again.

-Nigel