I just bought a 97 F150 4X4 4.6L, Auto Transmission. The transmission fluid is dark. It has 164,000 and probably never had a transmission service done.

Heres the deal, I have always done my own work to my vehicles and have
a well equipped shop to do it in.

The best technique I seen was somewhere on this forum someone explained how they took the return line to the tranny off and clamped
a hose on to it, ran out about 3 quarts and shut it off, pulled the pan that was now almost empty, and changed the filter and replaced the pan. Next he put the same amount of fluid he ran out back in, ran out about 3 more quarts, shut it down, topped it off and repeated the process untill the fluid came out clean. (also ran through the gears a couple of times)

Now this sounds easy enough, and I have replaced tranny filters before.
But is this a good idea on my truck, it has 164,000 miles and dark fluid?
and probably no service ever done. I don't want to cause any problems.
Some people say the detergent in the new ATF can loosen up too much stuff
and cause transmission failure.

Someone suggested a special high mile ATF, Is there a special or prefered ATF I should use other than Mercon?

 

set it on fire



just kidding, smell it if it smells burnt (like when you do a burn-out) then don't bother with changing the fluid the trans needs a rebuilt, if it's only dirty your still gonna need a rebuild soon but you might squeeze a few more 1,000 miles out of it.

if you do change it just drop the pan and change the filter.

 

How it the transmission performing in it's present state?

 

Polydorus:

It seems to be fine. No slips or slow shifting.

 

The 97 has a torque converter drain plug. No need to disconnect lines to get an almost complete fluid change.

 

You need to change the fluid. Period. Leaving contaminated fluid in your transmission isn't going to prevent failure.