I bought a vehicle couple of weeks ago. I checked the transmission fluid today, and noticed it was black. Should I be worried and immediately go change it? Part of me wants to get it changed since I have general rule of thumb to change fluids in vehicle I bought, and I am hoping that changing the fluid it will help with the transmission going into gear. I still need to warm it up, and see where the proper level is.

I am hearing mixed things on why not to change the transmission fluid, and some cases that I should change the transmission fluid.

So, should I change it?

Vehicle: 1991 Ford Explorer XLT.

  • Are there any transmission related issues? On older vehicles its better to let it be if its working OK. Changing the fluid might open a can of worms that will cost more than the total value of the car.
    – race fever
    Commented Mar 29, 2016 at 18:59
  • the auto transmission shifts into all gears fine, but I have to pump the gas a little bit to get going, If I go from park to drive, the vehicle will roll back little bit, and as im pumping the gas it will start to go.
    – andyADD
    Commented Mar 29, 2016 at 19:03
  • 1
    Hmm I see. You could try changing the transmission filter first (not the fluid) and see if that does not break anything. But do know there is a risk of upsetting the universe's delicate balance against your wallet. Do you have any info on the truck's repair history? At that age it should have had its tranny repaired a couple of times.
    – race fever
    Commented Mar 29, 2016 at 19:06
  • 1
    @racefever is right to warn you. Vehicles with high mileage which has never had the tranny fluid changed is at risk of complete transmission failure if you change out the transmission fluid. I understand this happens because the gunk in the tranny is the only thing keeping the tolerances together. When you change/flush the tranny, these tolerances are wiped out, leaving a lot of space where there was none before. Complete tranny failure soon follows. You won't know this until you change/flush the fluid. It is an utter crap shoot. Commented Mar 30, 2016 at 0:52
  • @Pᴀᴜʟsᴛᴇʀ2 I have learned a lot from you on this site, so I ask with complete respect and a desire to learn: How can tranny gunk, which can be flushed away by draining the fluid, hold a tolerance? (PS can't wait to tell my boss why I was discussing tranny gunk on the internet....) Commented Mar 30, 2016 at 13:41

1 Answer 1


Rough or slow gear engagement (as mentioned in the comments) could indicate that the shift solenoids are having trouble actuating due to the dirty fluid. As racefever suggested, you should change the filter, but other than having to buy new fluid, I personally don't see any reason not to change the fluid at the same time.

I would go ahead and change the transmission fluid & filter, even though it doesn't seem to be posing a problem at the moment. I've heard/read the same things that changing old fluid can dislodge debris and leave you worse off than you previously were. While I have never personally run into that problem when changing fluids for friends/family, it wouldn't have become a common concern if it never happened in the first place. As such, you assume an inherent risk when choosing to replace the fluid on a high mileage vehicle, but I am of the belief that if you do your research, have the right tools, take your time, and get the job done right (or find a shop that cares), it will be fine.

I attribute 'dislodged gunk' failures to quickly-lube style oil change garages screwing something up in the change/flush process, or using it as an excuse to cover their butts for more obvious oversights (ie replacing with used/improper fluid, filling to wrong level, not removing/cleaning the pan, using old/improper gaskets, forgetting to refill fluid entirely, under/over tightening the drain plug).

  • Check my comment above, and let me know If still should.
    – andyADD
    Commented Mar 29, 2016 at 19:20
  • Its like im gambling whether or not this transmission will go out, if I change the fluids or not. GAHH How infuriating.
    – andyADD
    Commented Mar 29, 2016 at 20:03
  • Do you plan on doing it yourself or taking it to a shop? Commented Mar 29, 2016 at 20:05
  • I unfortunately don't have too much time, with college and two jobs. I most likely will take it to a shop.
    – andyADD
    Commented Mar 29, 2016 at 20:06
  • 1
    @MooseLucifer Ok, I do not mean any disrespect. The answer you posted is a logical conclusion for people with casual experience with automatic transmissions. It worked OK for you then it should work OK for the OP. But we can't outright say the OP should change it because the times we've done it nothing happened. I would suggest to edit the answer and make sure to warn the OP (and others) that doing so could leave them with a big repair bill. I'm not saying you are wrong. Just saying that its prudent to be on the safe side of potentially expensive repairs. :)
    – race fever
    Commented Mar 30, 2016 at 13:51

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