Transmission flush or change?
 

I'm at about 120k now. I was going to change out the fluid and filter myself, save some dough, and learn in the process. But would it be better to take it to the dealer and get if flushed?

Thanks in advance.

I would take it to a reputable transmission shop instead of the dealer if you plan on flushing it.

A while back while talking to a mechanic who just rebuilt transmissions, I got on the subject of transition fluids and when and or what to do with replacing them.
Short story: If it broke don't fix it.
Per his words, unless there is an issue with the fluid ( burnt or another liquid contamination ) don't change it, re-use it. Filter it and put it right back in.
His suggestion - JUST clean the filter & clean ( and reuse ) the fluid and do NOT flush the system.
Why I asked..
Flising the system - does ( for the most part ) clean the system but that is not always as good as it sounds, lots if times the "dirt" basicly gets caught in the places that have light leaks and flushing the system could actually cause them to start to leak.
All NEW fluid - New fluid new distillates, with new distillates can after a while clean the same and might cause leaks too.
His words....
" Clean the filter, clean the fluid, reuse the fluid, and the tranny will still be good long after the rest of the vehicle fails...."
Just thought I'd share this - it's your truck and your $$
BTW i did ask if all this is a forgone conclusion - and no it isn't, it is just a possibility - but if it ain't broke don't fix it...

Change
 

For starters changing any fluid that has been used is literally getting a brand new vehicle. Not only will you notice the transmission shift smoother but it will glide downhills with ease especially when you let off the accelerator. You won't hear any gear noise, if the fluid is dark in color the. You should 100% change it and get a new filter. Please for the love of your vehicle do not re-use the same oil!!! If that was the case then why not filter your motor oil and dump that back in the motor? Thing about changing the axle fluids also. Way easier than changing transmission fluid and you will notice a huge difference on how your vehicle rides and drives and if you know how to do these fluid changes and are able to save yourself the money then what's holding you back?

Motor oil and trans fluid are two totally different beasts other than they are a petroleum product is pretty much the only thing they have in common.
New trans fluid works "better" because it doesnt have the contaminants in it (metal) keep in mind I am NOT talking about "burnt" trans fluid that is of corse bad and NEEDS to be replaced but there is nothing wrong with non burnt tranny fluid other thatn it needs to be cleaned of metal and any dirt. Unlike motor oil that gets "dirty" and the real reason motor oil needs to be changed, because it looses it's viscosity (the most important part of its use) the viscosity of trans fluid has prett much nothing to do with its use in your transmission its thickness does, dirty ( metal laden ) trans fluid runs hotter and makes the valves in the trans less responsive because its thinner (lighter weight) trans fluid is a hydraulic fluid first a coolant second and a lubricant last. Motor oil is a lubricant first a fluid barrier second and a coolant last. Point being trans fluid just has to be clean not "new" and by all means NOT "burnt" Will new tranny fluid hurt the trans, no, at the very least on a old trans there is a chance it might cause it to leak a bit that's it..

Drop the pan, replace the filter with a good quality WIX or AC delco filter, refill with high quality ATF. I would not flush.

Thanks Phil. Sounds like a plan. I was planning on using Mobil 1 Synthetic ATF fluid. Will that cause any issues with the existing fluid in the system?

Nope Mobil 1 Syn is great and fully compatible with what you have in there now.

as always, thanks again Phil!

Can I have a pic of this Mobil 1 Syn? Found a few type under the same title. Thanks in advance.