Fluid changes and Transmission question

Hello,

I have 167k on my truck and still going strong. I've never changed the transmission fluid, and I would like to do so soon. My reason for waiting so long is that I've always been nervous messing with transmissions. I can't seem to get a straight answer regarding a flush vs change, and I'm not really sure which is best. Any help would be appreciated!

Also, what other fluids would everyone recommend changing? I was thinking about coolant change but I'm not sure if thats something that needs to be done. The front/rear diffs were changed around 100k miles.

Thanks!

 

With the amount of miles you have I would do a few drain and fills. Then after all that I would do a full flush with filter clean/replace.

Edit: not a bad idea to do a coolant flush as well as transfer case

 

With that many miles, most say not to do it. A lot of transmission die after a service with that many miles on it

 

I would think long and hard before I flushed the AT fluid. If you're not sure talk to some pro's. if the fluid is really brown and smells burnt. . . run it until it dies.

 

Geez, have you changed the motor oil?

That many miles, you should be starting your 3rd coolant flush; third ATF flush; and 4th, 5th or 6th gear oil drain/refill - depending on whether you are using synthetic.

I agree, do not do a full ATF flush ... drain the ATF; drop the pan and clean or replace the ATF filter, then refill with ATF; it'll take 3-5 quarts, depending on much drains out. If the tranny runs the same or better, do another drain/refill in about 30K miles. Then another. At that point, if tranny is running without any issues, your truck should be OK with a full flush.

Or, do what @gearcruncher recommends; he is a resident tranny expert.

Your cooling system should be flushed out chemically. The coolant has likely long run out of it's protective corrosion and acidic inhibitors. First, replace the hoses and thermostat. Top off with distilled water and take the truck to a trusted radiator shop to flush out the cooling system.

https://www.cars.com/articles/2013/05/does-engine-coolant-go-bad/

While you're at that, replace the serpentine belt if it hasn't been replaced. And check each idler pulley; I'd bet you have one or two with some freeplay, an indication the bearings are going bad. #1 idler and tensioner pulley bearings were the ones that went first on mine, at about 150K. Replaced all the bearings in the pulleys for good measure.