I have heard some things concerning the servicing of Transmission Fluids and Filter Change Nightmares on most older vehicles. My 1993 Ranger 4.0 XLT is running quite fine and effortlessly with respect to the Transmission. I noticed that the Transmission fluid is dirty and oily looking, and its overfilled pretty much for almost a year now, when i had purchased it.
So, I let it be for a year. Do i change the Trani fluid and the filter, or just leave it be. Im thinking the previous owner may of used some special magical snake oil treatment in the Trani to keep it stable, or up to par etc. However, Im not 100% sure. Should i just leave it be or change it and change the filter? My intuition says yes leave it, if its not broke dont fix it.
What do you guys think i should do.

 

Mileage on the vehicle or transmission itself, if it differs, always helps us think.
Ownership timeline can help too. Was the previous owner the original owner?

Since you know the fluid is "dirty and oily" I'd do a pan drop. This'd include a filter change.
The 5-6 quarts which will drain constitutes about half the fluid.
I installed a Dorman replacement pan (part # 265-831) with a drain hole @ 48K. along with a new filter. This was when the truck was 16 years old.
I wanted to inspect the fluid -it was darkened and dirty but not disgusting- and check for debris in the pan -there was none. I felt happy to dilute the dirt.
Refreshing half the fluid isn't the dread shock some inappropriate machine powered flush or use of incorrect fluid is.

In all likelihood I'll do another sump drain without filter replacement in 30-40K miles.
Assess your dirt content. Drive the truck a while before deciding if more "dilutions of dirt" are necessary.

Since you're overfilled, you have the option to inspect the fluid and pan contents then return the correct amount of old fluid if you like.....just use a clean catch pan.

Also keep in mind that people commonly service a transmission after it has begun failing. This is where many "Clean fluid destroyed my trannie" stories come from. Their units were already on the way out..

 

Thank you for that great info. However My mechanic said to drain it to the normal fill line and add Lucas Transmission Fluid.

 

I drained it on Sunday, and actually had to add some more regular trans fluid. I also threw in a little marvel mystery oil as well. No issues so far....

 

You made fun of "snake oil" then added some yourself?
MMO has no place in a transmission. What fluid did you use, MerconV?
How filthy was it?

 

Mercon V, with 4 oz of MMO, and in what I have read online, it's safe to use. Only small amounts are recommended. 4 oz was all I added. As far as snake oil goes, it works for me in my fuel tank and in the crankcase. It actually had unclogged sticky lifters for me. Its a mystery but it works. FWIW, The company has been around since 1932. That's pretty long for a snake oil company, don't ya think.

https://www.marvelmysteryoil.com/faqs/#:~:text=in%20auto%20transmissions%3F-,Answer%3A,MMO%20in%20the%20automatic%20transmissi on.


https://www.autoguide.com/best-transmission-fluid-additives

 

Needless to say, the transmission is shifting pretty good. And now I have a mixture of old Trani fluid with a quart of new Trani fluid and some mystery oil. Less is more as I didn't want to totally remove all the old Trani fluid.