My aero has 187k miles on it. It runs and shifts well but the tranny fluid looks barfy. I am going to replace the filter and would like to do a total fluid change instead of just draining the pan. This will give me a warm fuzzy feeling knowing it's got clean fluid.

I have searched this forum and read numerous threads regarding flushing but the results are inconclusive as the best way to do it.

I bought some tubing to connect to the lines in place of the transmission cooler. I figured I would run the return line into a bucket of new fluid and the other line to an empty bucket. Then all the nasty fluid should fill the empty bucket and it will suck up only clean new stuff, right???

Now, should I drain the pan, replace filter & gasket BEFORE -or- AFTER doing the above fluid change?

How should I go about flushing the tranny cooler or will it just drain with gravity?

Also, what does the tranny modulator do and should it be changed?

I bought 3 quarts of fluid the other day and then went back and bought 3 gallons. I bought the cheap autozone "coastal" brand Mercon stuff. So I guess in total I have 15 quarts.

Thanks!

 

Flush before you change the fluid, you'll have to drain the good fluid to change the filter. That way, your new filter will not have had any of the old trash pushed in it.

 

I've done mine several times. I'll let the fluid drain out at the cooler as you describe, but I add the fluid to the transmission at the dip stick. You'll need a helper to start and stop the engine as you do this, as it's hard to keep up adding the fluid. If you connect your tubing to he outlet side of the oil cooler, you will flush it at the same time.

I use clear plastic tubing and watch the fluid coming out. When it turns bright and clear, you can stop flushing.

I usually use around three gallons for this procedure.

The modulator doesn't need to be changed unless you notice evidence of transmission fluid in the vacuum line it's connected to, or that the tranny is shifting abnormally hard.

I change my filter first, but I don't think that it really makes much difference. You'll waste less oil if you change the filter first.

 

Its true, the modulator does not need to be changed, but should be, since they do stick sometimes when they get old. Its a cheap part, and its just better to replace it. But you can wait till it ruptures and that is ok too.

 

On a 1992 Aero where exactly is the mod?

 

I tackled this job a couple of days ago, after reading the how to hints here. Didnt have a torch to solder copper with so did this:

Obtain a compression type tee fitting sized for 3/8 OD tubing.
Insert a 1 and 1/4 inch piece of tubing into each side of the tee.
( I happened to have some grey plastic water tubing, but use whatever, preferably sort of stiff.)
On one side of the tee, put 1 and 1/4 length of 3/8 INSIDE diameter hose over the 3/8 OD tube, hose clamp it.
Out the bottom of the tee, use about 1 foot of clear flex 3/8 tubing, attach a cheap compression drain valve on it.

There is room to separate the steel cooling line from the rubber hose to put the tee in between them. Hose clamp it in place.

This worked so simply I kick myself for not learning about the gentle flush years ago.

 

just watch your old drain out ATF...when it changes from dark stinking goop to titty pink new, you're done

I'm cheap and a simple DIYer, I just pull the out line off the ATF aux cooler and nipple extension it into a bucket, back on when done.
no fuss no bother no fittings to worry about

 

If you mean schedule 80 pvc pipes when you refer to grey plastic water tubing, you should know that most pvc water tubings are not rated for high temperature fluids, just cold water.

Also, make sure the valve is properly supported, as I've had compression fittings leak due to vibration, and copper lines crack, again due to vibration.