This is my point there does not appear to be a recommended interval

 

no and never are ez to say, im looking for a tranny man who can tell me why it would/not hurt for a few /10/20 seconds.
I first admitted my lack of knowledge. I want someone who actually knows trannys, no opinions. everyone has one!

 

Posted this a while ago but this may help if your going to tackle this yourself.

Well I did the fluid and filter change this morning, this is how I did it and it seemd to work fine for me,
I did this on the driveway with the front on ramps and the rear on the ground, the angle of my driveway keeps the vehicle level. It should be as level as possible for this.
Drop the skid plates, remove the transmission cooling line on the left (drivers)side of the bottom of the radiator,
There is a plastic retainer ring you slide back with a screwdriver, then you need to remove this tiny wire spring clip that holds the aluminum tube in the radiator. DO NOT LOOSE IT!. swing the tube down out of the clip and pull it back out of the radiator. Fluid will start to run out be ready.
Put a peice of tubing on the removed tube and secure it so it is aimed into a 5 gallon bucket. If you can have someone start the engine while you watch the fluid pump out, as soon as you see it sputtering shut the engine off. you should have about 5-6 quarts in the bucket.
Now you can drop the pan, there will be about a quart left in the pan, less messy than just droping the full pan.
Drop the pan, clean it and the magnet and get the gasket ready to go back on.
Pull the filter down as you wiggle it side to side. look up where the filter tube goes up into the transmission and replace the seal in there (if it came with your filter and gasket). a little tough to get out and I found a socket that was exact size of the new seal and I tapped the new one in with the socket and extension.
Replace the filter and reinstall the pan. be sure to torque these properly as to tight will deform the pan and it will leak.
Now add 5 quarts of trans fluid and have someone start the engine and you need to have 3-4 quarts ready and open to start pouring in the fill tube as soon as the engine have someone watch the fluid pumping into the bucket in 4-8 seconds you will see clean fluid comming out,
Shut off the enging as soon as you see clean fluid,
Reinstall the cooling line into the radiator, be sure to get that little evil clip back in properly and slide in plastic retainer clip back on and your done under the vehicle.
Fill the transmission with the engine off until you see the proper level on the dip stick.
start the engine and with your foot on the brakeshift to D and then back to R waiting about 30 seconds in each, do this a few times and recheck you fluid level.
Get it up to the cold level while the oil is still cool, engine running and in park.

Take it for a easy test drive and when it is up to operating tempature recheck the level of the fluid while the vehicle is running in park and on a level surface.
I had 12 quarts on hand and wound up using about 11 (depends on how much you let it pump when the clean fluid starts comming out)
Dont forget to put the skids back on,
This methiod worked well for me, I did the same procedure on my Envoy 6 months ago and all is well.
Good luck
and just ask if you have any questions, I will be happy to help if I can.
John

 

very good info on using the tubing to drain the tranny till it sputtered. empty I assume.

do you think that is about the same as dropping the pan and running for a brief time to empty the tranny?
I am real curious just what could get hurt by a brief run when empty,not someones guessing but actual facts from someone who really knows tranny s.

 

its not going to be a good idea to run the engine/shift through the gears with the pan removed. The oil that is on the gears lubricating it will be flung off immediately and your gears and seals will not like being run dry. Follow the steps above to get all the old fluid out. Running it until it sputters does not run it completely dry, hence having to do it a few times. You shut it off AS SOON AS you see it start to sputter, do not try to get it good and empty.

 

There is a proper way to flush the trans fluid by using a catch basin and a pump, so there is a continuous flow, so that you don't run the fluid dry. Yes, people have a lot of opinions and sometimes they are just trial and error which can sometimes damage your vehicle. I would do exactly what a trans shop recommends what I just said above so not to risk your expensive transmission.

 

just don't forget that many transmission shops recommend a power flush of the transmission. I'll let everyone hash out the pro's and con's of that one.

 

Cool, info, it seems I am heading into the capital city (Sydney) in a few weeks time, I think I will just book the H3 into a reputable transmission workshop to get the filter changed and the transmission flushed.

I do most work and servicing myself, but I think it would be pretty safe to get someone to do this for me, especially if I keep an eye on them while they do it.

 

That's what I said rsc. That's what they recommend.

Aussie, it's not that hard to do. With all you have done to yours I think you can do it. Scheduled maintenance is in your owners manual Aussie. Change the transmission fluid between 50 and 100,000 miles depending on the driving you do.

 

meantime im still ploughing thru the paper pages of the official gm svc manual, trying to find any procedure they recommend.
anybody know if its in there? I cant find it.

three books,11lbs, 8 inches thick!! it otta be there