Mines a 4T65E HD and it took at least 7 quarts.

Andrew...look at your avatar and don't do it.

I buy 2 gallons and on my 65 I've had some left over...don't know exactly...but it was around 2 quarts.

Either way.. if you pick up about 2 gallons you can complete a service and top it off.

Mine being the heavy duty would explain it for mine, but wouldn't for my son'* '99 GP which is not supercharged and has the 4t65E. I'd go with Bill'* suggestion of having 2 gallons (8 quarts) available, just in case.

I filled mine to the low mark then start the motor and keep checking it and adding up to the low mark. Then I drive it to warm it up on roads close to home. When tranny is warm I fill to the full mark. Then check daily as I drive it.

Last time there must have been an air pocket because it dropped below low enough I got clutch slippage on one start. Came home checked and it was lower. Just don't overfill for when it'* truly warmed up.

I changed my trans fluid about 4 times last year, less than 6 quarts with filter change. The only to get it all out is with a flush, takes about 30-45min and costs about $120ish.

I wonder if the ramp angle has any effect on how much drains out? If it were steeper maybe it would drain more?

As long as I never have to worry about this soon I am happy. I like how everyone helps everyone out, although it is sledom I know something of vaule of importance besides 04-05 stats, information and hp and tq figues lol. But I love it here anyways, and I drive a N/A 05 SLE and I wouldn't rather have it any other way!

That could be. I use pretty steep ramps, and where I do it is also on a slight incline. I also let things drain a while I'm off cleaning everything up.

Holy smokes

For that kind of money; I'll drop the pan, let it drain all over my face, and maybe even drink some. Then I'll pocket the left over $100.00 and maybe buy something off the MAC truck.

$120 isnt that far off from around here... i was quoted $89.99...

remember a flush removes all fluid, while a pan drop does

drinking the fluid would result in having no time to play with new mac tools

and 120 is what I paid at the dealership south of Seattle. Only $89cdn up here at Canadian Tire during the spring service special.

Dropping the pan and changing the filter is a good idea but a flush goes way beyond that and pulls all the fluid out and filters it up.
On a higher milage car this may loosen up varnish and fowl up your valve body, most service shops will ask in advance.