Power Flush or Drop Pan? - Hey guys, I have around 65k on my 07 and was going to do a tranmission service at the dealer. He said that GM ...

Hey guys, I have around 65k on my 07 and was going to do a tranmission service at the dealer. He said that GM suggest to "Power Flush" the trans ($199). Evidentaly a machine is hooked up to the trans that flushes all of the fluid and lines on the transmission to get most of the old fluid out. The filter is not changed but is flushed backwards. The service manager stated that to drop the pan and change the filter will not get all of the old fluid out and is only recommeded by GM for high milage vehicles. Has anyone had any experience with either of these processes or can someone tell me the best method to use? Thanks.

Not sure on that one. I've never done a power flush before, i've always just dropped the pan and replaced fluid and filter. I've not done one personally that new of a truck either, the dealership did my wife's 08 Tahoe last time @ 40,000 miles and they did replace the filter. I think it was around $150 bucks (glad she paid for it). This probably doesn't help much but thats my 2 cents...

I just serviced my tranny and the service manual states nothing about doing a flush, just the pan-n-filter. I don't think you'd need to replace ALL the fluids since GM doesn't require it at each change. The introduction of a few quarts of new fluid should be enough to replenish the additives when done regularly.

I've heard several stories about full flushes causing issues later from the new detergents washing away varnish that built-up and protected certain areas, and it washing away other sediment which later caused blockages.

Just did a flush on mine at 80,000 miles on my 08. I have done this process before on other trucks and have never had a problem. I went synthetic on the new fluid along with transfer case and diff. I tow a camper and snowmobiles and as you can see do a lot of highway miles. My thought is if its clean fluid its probably better than the dirty fluid that is breaking down.

The filter is not changed but is flushed backwards.

You be the judge if this is a good idea..

Bulletin from Filter Manufactures Council

Some people believe that all transmission filters are backflushed clean every time the vehicle is turned off. This is a major misconception. Three-quarters of all transmission filters today are not a simple screen, they are made of felt. A felt filter CANNOT be backflushed. Felt holds dirt particles within tiny pores in the felt. It will not wash out or flush out. If a felt filter becomes clogged it must be replaced. Clogged filters restrict fluid flow, which lowers pressure to clutches and bands. This can cause slippage and eventual burnout of the transmission.

There have been an increasing number of instances surfacing recently regarding transmission failures shortly after an evacuation service, without filter removal. At the time of a fluid evacuation service, there is no way to know the condition of the filter and how clogged it may be. The filters job is to collect and hold contaminants, (dirt, metal filings, friction particles, etc.), and prevent these particles from causing malfunction in such components as electronic force motors and solenoids. Today's transmissions are far more susceptible to malfunctions caused by fine dirt contamination. Without servicing the filter, there is no way to know if the filter is clean of debris or nearing capacity. If the filter is nearing capacity, transmission failure may not be far off. This is also a sign that there may be other internal problems in the transmission. Recognizing these warning signs could eliminate major service later.

Even if the fluid evacuation method is desired to remove the used transmission fluid, the pan should be removed also, and an inspection should be made of the pan contents, fluid, and filter to determine the condition of the transmission. Aluminum filings in the pan or iron filings on the pan magnet are signs of internal wear and may give light to potential problems in the transmission. Transmission service is performed for preventative maintenance. Evaluating the overall condition of the transmission by removing the pan should be part of this preventative maintenance also.

soon we can start backflushing our oil filters...

Well you guys convinced me to stay with the old drop the pan and change the filter even if I leave a little fluid in the tranny.

uneasyrider wrote:Well you guys convinced me to stay with the old drop the pan and change the filter even if I leave a little fluid in the tranny.

I just did a flush ...had the dealership do it. I plan on doing a pan/filter next year. I went with the flush since I bought the truck used and had no idea how it was used. It did appear the truck was used for some towing duties (it certainly has all the right options) ...maybe a nice bass boat. Anyway, I did the flush basically to "reset the clock"; now I know when it was serviced last. Next year I'll have the shop drop the pan and change the filter.

Tranny fluid is great stuff; works good lasts a long time ....unless it gets overheated. Once the fluid has been overheated, all its good properties and its ability to protect the inner workings of the tranny degrade quite rapidly.

Just adding my 2 cents to the pan drop/filter change question...I was quoted $389 from my local dealership to drop the pan and replace the filter. I about pooped myself. I went to my local AC Delco shop and got a filter for around $40 and grabbed 5 quarts of Dex VI for about $7/quart. I used a suction device down the dipstick tube to suck out most of the fluid and then dropped the pan. If you can do it this way, there was less than a quart in the pan when I dropped it and it didn't spill at all. The AC Delco filter I bought came with a pan gasket and a new o-ring for the filter. If you do this yourself, I would highly recommend not messing with trying to replace the original o-ring unless it is torn for some reason. The o-ring is actually a metal ring that has a rubber coating on the inside. I tried pulling the old one out with a pick and ended up ripping the rubber and bending my pick, thus forcing me to have to remove it. I ended up using a seal removal tool made for pulling axle seals. Let's just say that that metal ring is in there tight and I bent the tool before the ring came flying out with one last desperate yank. I don't even know where it went. I still haven't located it. Probably behind my workbench. Anyway, the new ring had to be tapped in with a brass rod and a hammer. Major PITA. Leave the seal alone. Pull the old filter out and pop the new one in. If you do that, it is a pretty straight operation and can be done by anyone with the right tools and a little knowledge about working on cars. With tax it cost me just under $100.

So it sounds like the drop and replace is the thing to do. Has anyone tig welded a threaded coupler with a plug on their trans pan for easy draining purposes? Also is synthetic trans fluid the way to go?