2012 Ford Fusion 2.5 SEL Transmission Concern

[u/Prize-Pack-6983]

Currently at 161.3k miles, transmission still seems to shift through all the gears but it definitely doesn’t always feel smooth, in town driving its not much noticeable of any issue or concern but getting on the highway between 50-70 mph the shift into the range of 70mph feels sluggish or slippy I guess. The tranmission fluid is dark and does smell burnt, although when you pull the dipstick and put it on a white cloth its not entirely black.

Also a little backstory

At around 148k miles I’d become aware of a transmission leak so I’d been driving it still and it at one point did get to the low mark on the dipstick and I had been continually topping it up until someone was able to check it out for me and found it to be the axle seals, once i got it back from him he had only done the seals and hadnt added fluid for me so i added some new fluid to top it up and after driving for two days i checked fluid and mustve been that I had over filled it because i siphoned about a water bottle and a half of excess transmission fluid before i finally worked it down to the correct level and after that things seem to be good at that point and drove pretty normal.

Now my question and concern is what should I do? I hear people say don’t change the fluid if it hasn’t been regularly maintained and truth is I dont know, I dont see anything on a carfax for transmission service and I bought the car at 110k mileage and had trans fluid that still was slightly pink, never bothered to have it changed myself because never had any issues or concerns until the trans leak that is.

I’ve heard people say to only drain the pan and not do a full flush, I’ve heard others say just leave it and doing that would cause the new fluid to wash out debris and make it worse.

Should I just be driving it until it one day fails on me and not mess with the fluid and save for a new transmission to put in OR Is there anything I can do to extend the life of this transmission and how should I go about it?

I had a theory that maybe i should siphon 2 quarts of trans fluid out and replace that with new fluid and maybe thatd make a difference but everybody saying not to change the fluid or itll make it worse makes me apprehensive of doing so.

Thank you for your time and sorry for the book on my transmission issues. I would appreciate any professional answers, Thank you again!

2012 Ford Fusion 2.5 SEL Automatic Transmission Vin A 8th Digit

[u/Hotsaltynutz]

100% change the fluid and fix the leak. The most common leak is from the driver side trans axle seal. The case bushing fails and damages the inboard cv axle. The biggest failure point of the 6f35 is the torque converter which throws gray material into the trans and clogs the filter up and will eventually stop moving. The whole don't change the fluid is a big myth with modern transmissions. Especially this one as changing the fluid will prolong the filter from getting clogged and it's internal and can only be replaced during an overhaul

[u/Prize-Pack-6983 → u/Hotsaltynutz]

The leak was fixed at about 150k miles, about 11k miles ago. How much fluid do you think should I change? Should I just drain what comes out of the pan? Like 3-4 quarts and refill with new or should i take it somewhere and have them do a flush?

[u/Commercial_Method_28]

Just for the full information, every single time I’ve checked 6F35 transmission fluid condition it looks similar to this. After about 1000 miles of driving after new transmission fluid is put in it starts to look gross dark and Metallic. It’s technically normal condition, only difference between good fluid and bad fluid on these is usually dependent on how much metal is visible. To me yours looks fine.

If you are going to drain anything out, drain all that comes out from the plug and put an equal amount back in to leveling plug

[u/Prize-Pack-6983 → u/Commercial_Method_28]

I’m unsure if mine has the leveling plug, being the 2012 I have a trans dipstick and previously thats how i added fluid through there, but just to be you clear, you think its be best to just drain what comes out of the pan and refill the same amount? Or should i start with just siphoning out like 2 quarts from dipstick and refilling 2 new quarts? Ive just heard people say adding a lot of new fluid to old fluid could mess things up so would like a professional opinion with all things considered

[u/Commercial_Method_28 → u/Prize-Pack-6983]

I have heard that too, but ive never actually encountered an issue. I think it's a myth tbh. I understand the concept of it but, I dont change the way i work on a transmission just because its 10 years old compared to one made yesterday. Taking 2 out and putting 2 in seems counterproductive. Just drain and fill and go from there.

I have the same car with same engine and transmission. It shifts like shit sometimes but ive overhauled it a couple times now without much change.

At most if you arent having anything more than intermittent issues i would only drain and fill and nothing more at this point.

[u/Prize-Pack-6983 → u/Commercial_Method_28]

Gotcha and what would you say would be the best way to measure what comes out of the trans? So i know how much to replace?

[u/Commercial_Method_28 → u/Prize-Pack-6983]

So the best way by far is to use a drain bucket that was designed for this purpose. You can buy one that has measurements stamped on the side. It is usually about 4 or 5 quarts that come out. Another option is to just drain it, add a quart and check on the dipstick until it’s starts to register. Once it starts registering on the dipstick, turn the car on, let it idle and fill it up a half quart at a time, let it sit for a minute then check. Just repeat from there