Hello Scotty, Love all your informative Videos, learned a lot from them, thank you for your good work, i have a GMC Sierra 2013 SLE it has 146136 miles, im the sec owner, 8 Cil. 5.3 L--- I have never replaced the Transmission Fluid and Filter, when should i Replace? and if i do, what kind of Fluid should i put in? (buy from Chevy Dealer or Local store?) and if i do it should a Replace the fuid completely or just replace the filter and put in the same old fluid? Help! Thank you!
As the second owner, you don't know (without service records) if the fluid and filter have been changed. I would change the fluid and filter now and start and stay on your own maintenance schedule as per your owner's manual. You might also want to consider changing out the coolant, brake fluid, power steering fluid and rear differential hypoid gear oil as well if you want you vehicle to last a long time.
Check the condition of the fluid. If it is burnt and gritty it is best not to replace it since the friction of the suspended grit may be all that is allowing the trans to function. On the other hand, if the fluid is no worse than dark red it should be safe to change. Type of fluid would be documented in the owner's manual but it is most likely Dexron VI. Any good brand (Valvoline, Castrol, etc.) is fine. You'll want to do a drain and fill rather than a flush.
Your owners manual should have the info on what type of transmission oil you need. I don't know if your manual says what filter to use but Amazon seems to be helpful determining what fluid and filter you would need but you should look at other sources to confirm what you need. Your dipstick might be labeled as to what type of fluid you need also. Anyway, if the fluid has never been changed Scotty would probably advise against changing it at such a high mileage - but I don't want to speak for Scotty - he does have some youtube videos about transmission fluid changes.
