Good afternoon ladies and gentlemen. If this has been posted before, I apologize.

I have a 2008 SD, with about 180k miles. I’ve had it since 152k. In those 3 or so years, I haven’t had any major issues with the transmission. I have been told by the dealership when they’ve had it for other reasons that my trans shifts hard but never gave me any reasons or ways they could solve it. I am now starting to notice the hard shifts and I wonder if it’s to late for a flush. I had a local shop tell me if I’m feeling the hard shifts, it’s too late for a flush and they wouldn’t touch it due to issues possibly arising after the flush. However he did say I should take it to Ford and have them run a scan to ensure the shift points are correct and they could tell me what route I could go to fix said issue.

now, I do have a tuner on it, but I wouldn’t think the tune would all of a sudden start causing these hard shifts, unless I just don’t drive it hard enough for the tune.

My question I guess is, is it worth still doing a flush?

what about draining the pan, adding some Lucas treatment and topping off with AT fluid?

the research I’ve done shows a flush can literally go either way. Some say doing it will be beneficial, others say it’s too late.

 

The first thing to do is to see if there are any codes stored. The suggestion to scan to see if the shift points are good is a suggestion by someone that doesn't know ANYTHING about this. That's not possible.

A flush or even changing what's in the pan isn't going to make the trans fail. While it is possible that the trans will fail right after a flush the cause is that the trans has been neglected until problems arise. Then a flush is done, and the flush can't fix the parts that are already broken inside the trans so it fails. It would have failed without the flush, too.

I do not recommend additives.

 

Thanks for the response. That absolutely makes sense. I’ve also heard about a “back flush”. Is this actually a thing? I wouldn’t think so as there are ports and such that act as check valves and don’t allow fluid to flow both directions.

 

I hear a lot of talk about backflushing. It's impossible. End of story.

 

Thank you. As I’m driving and testing different theories (heavy throttle, light throttle) I notice it doesn’t shift as hard in the heavy throttle. Lower throttle is even just above slightly noticeable and annoying. It’s not like it’s slamming into gear. There aren’t any codes, and I think it’s just time to change the t-fluid, as I doubt it was ever done. Thanks again for the reply and help.