Ok so heres a first.....lol. Have a good mechanic for the jobs I cant do, or " cant finish" after starting.
Guy has been great to many of us for years. Been oressed for time lately so I took H3 in today for 50k service. Front & rear diff fluid, trans fluid & filter. Asked if he can locate exhaust leak that I suspect is the manifold .

He calls and tells me leak is before the cat, needs time to get in there and find it and.... no need for the trans service? It looks great... wasting my money. What?? Lol. How often do you guys change trans filter & fluid? Its been about 50k since last time with 128k on the clock now. I'm all about preventive maintenance, am I being neurotic? He did the F&R diffs, seal replaced in rear that was leaking. But he did not do the trans. Told me its not needed, wont rip me off by doing it.
Shes not beat on, have an easy 12 mile ride on highway each way to work, no towing, not abused. I'm thinking 50k it needs to be done...no??

 

I do it every 50K. But I wheel and have larger than stock tires. I monitor my trans temp (it gets hot!) and the fluid may look good but the viscosity breaks down over time. Heating and cooling, heating N cooling, heating & cooling. You get where I am going with this.

 

an old post showed how to pump out thru a cooler line. worked great" 4 me,got it all. trannys love to be serviced. best money you can "waste" on your ride!

 

I change my oil ONLY when the GM OLMS pops the message to do so.

Per the Owner's Manual, Trans Fluid & Filter should be changes every 50K miles when in severe service, or every 100K miles under normal service.

Severe Service per footnote h:
"(h) Change automatic transmission fluid and filter if the vehicle is mainly driven under one or more of these conditions:
− In heavy city traffic where the outside temperature regularly reaches 90°F (32°C) or higher.
− In hilly or mountainous terrain.
− When doing frequent trailer towing.
− Uses such as found in taxi, police, or delivery service.