Nice thread.... but here are a few thoughts from my perspective.
1. Yes, the filter needs to be serviced, the dump drain, and refill method just isn't enough. As the filter plugs up, the line pressure in the trans goes down, and friction material wear increases.
2 .Dex VI is one on the worst fluids GM ever came up with. It was mandated to meet a ultra low viscosity requirement from the upper brass, to try to raise fuel economy of the GM fleet. Its not known for good shifts, or prolonging transmission life. I own several GM products in my personal life, as well as the company I own. The first thing I do when adding a vehicle is dump out that DEX VI.
So, what to use then?
Allison Transmissions (a division of GM) had Castrol invent a "Super Dex VI" to address the shortcomings of DEX VI, and boy did they deliver! The fluid is known as "Transynd", and carries the identifier TES-295. Several companies make a licensed version, they are listed here.
http://www.allisontransmission.com/p...highway-fluids
Here's how I service a GM / DEX VI transmission.
1. Drain pan, remove pan, replace filter, install pan.
2. Fill with a TES-295 fluid ( I use Mobil Delvac) Get the level close, but you dont need to be exact. Run the car for about 5 minutes and then drain the pan again. ( no need to drop the pan, just drain it) This is known as a "Double Dump" and will swap out about 90+% of the fluid. Now refill it again, and do spend the time to get the temp up, and set the fluid level accurately.
And that's it. This fluid is designed to go a minimum of 100,000 miles, in city buses, dump trucks, and other HIGHLY stressed applications where DEX VI would fail in no time.
For anyone wanting more info on TES-295 fluids, here is good read directly from Allison:
"When using Allison Lube spec TES 295 fluid, change intervals should be as follows:
Fluid life: 150,000 miles / 6,000 hours
Lube/Auxiliary Filter (if used): 75,000 miles / 3,000 hours
Internal Filter : Changed only during transmission overhauls
Initial 10,000 mile change:Not required with TES 295 fluids
Using any oil not listed as TES 295 approved or a non-Allison genuine filter may void your warranty.
Also note that effective January 2010, per Allison Service TIP 1099N, Allison no longer authorizes the use of DEXRONŽ III or IV in any of its transmissions."
As always, do your own research, but I've yet to have ANY transmission issues since switching everything over to a TES-295 fluid.
