Bought a used '11 w/ 140k, leave the trans or change fluid/filter?

[JasonPAtkins]

I realize there are conflicting schools of thought on older transmissions and whether it's better to just leave them alone or try to service them. Advise specifically related to these transmissions is welcome.

I bought a 2011 Avalanche with 140,000 miles. I have no service records for it. I'm outfitting it to be sent to a remote part of West Africa and want to do all of the major stuff I'll need to now while parts are easy to get.

I have no idea whether the trans fluid was changed at 100k. Any guess would be a guess. Looking at the fluid on the dipstick, it's not red (was when new, right?). It's color is black, but it's not thick black like used motor oil. It's still fairly translucent, but the color it does have is definitely not red.

I think I tend to agree with the "don't flush a trans over 100k" camp, but given that in this case I have no idea if it was ever changed, it could still be the original filter in there holding on to filings that were created when the brand new parts were driven the first 100 miles of the vehicle's life.

So, given that and the fact that the fluid isn't red anymore, I think I'm leaning toward the procedure outlined here that changes all of the fluid (and filter and gasket) but doesn't do so under pressure like a flush would.

Does that seem like a reasonable middle ground option? I called the dealer today, and they sell Dex6 bulk for $3.50/qt if you bring a container for them to pump it into, which seems pretty reasonable.

 

[Doubeleive]

if it were me doing this I would do the transmission service and then drive it a bit atleast 3-4 days of good driving to be sure nothing fishy will take place afterwards, but that's just me ive had both good luck and bad luck, usually the bad luck was on much older vehicles.

 

[CobraKing]

@JasonPAtkins There's a few people with used ex-Police Tahoes (like myself) that have just done drain and refills. There is a noticeable improvement in shifting and operation temperatures from that alone.

 

[JasonPAtkins]

@JasonPAtkins There's a few people with used ex-Police Tahoes (like myself) that have just done drain and refills. There is a noticeable improvement in shifting and operation temperatures from that alone.

Interesting. I don't notice any hesitation or slipping while shifting. The DIC reported trans temp is right around 120F when on the highway (not towing, obviously). So I don't see any warning signs that are making me ask this question. It's just that after I send it over to Africa, this kind of service will be a lot more difficult, so if it should be done in the next 50,000 miles, I want to do it now. However, there's the flip side of the possibility of doing this then it developing a transmission problem right after it gets there because of it.

What I'm asking though, is that it seems to me like the fluid/filter change is much less dangerous than a flush, because it's not moving fluid through any faster than the trans does in normal operation, so it's not going to dislodge anything like a flush could. I don't know if that's correct thinking or just sounds good though.

 

[CobraKing]

I'd seriously rethink sending a GM truck to a remote part of Africa vs. doing a drain and refill on the transmission. Have you thought of sourcing a Toyota truck or at the very least a Nissan or Mitsubishi?

That said if you have no idea about previous maintenance or driving habits I would take the simpler, cheaper route of doing the drain and refill.

My RWD truck prior to having the ATF drained and refilled was showing 79C on my 45 minute commute to work (mainly highway) and after was showing 55-56C. Shifting is way smoother too.

 

[swathdiver]

The Transflow machine used at GM dealerships will clean out the pick up screen, then the tech reverses the hoses and does a fluid exchange.

If I were using the truck in a remote location, I'd want it 100% before taking it there. If it were my truck, I'd change out all the fluid and drive it around a couple hundred miles before declaring it ready for the boonies.

 

[techbiker]

If your transmission fluid is black, I wouldn't drive until all of the fluid has been exchanged. I would replace the filter, service the pan and magnet, and perform a full flush at a dealership or by using the home method. Make sure to use Dexron VI and hope that your transmission hasn't been permanently damaged.

I blew out two automatic transmissions on my Z. The first went out after the fluid turned dark brown. The experience motivated me to swap in a manual.

 

[Clive]

I'd second the concern that 'black' tranny fluid should definitely be addressed asap. That's quite unusual - I did a 2000 Yukon at 140K and it wasn't black, but a red-brown color. Maybe your's has done a lot of towing? Black fluid at 140K suggests it's never been serviced.

I use the well-tried process that pumps out the old fluid via the radiator top connection. I also drop the pan to inspect debris, clean the magnet, pan, and replace the filter+gasket. It's not failed me yet, and I dont know of any drawback to doing it this way, other than time and money (about 2hrs and $160 for 12qts DexronVI and a new filter). I certainly wont take any vehicle to a lube shop to have a 'transmission service' done where they just pump/flush via the dipstick. Did that once on my Dodge Caravan at 80Kmiles and the tranny broke pretty soon afterwards....

Just done our current 2011 Hoe at 75K, and concluded that wasnt too soon. 100K would have been way-over due, think I'll stick to every 50Kmiles. I posted pics of the pan condition.

 

[techbiker]

I'd second the concern that 'black' tranny fluid should definitely be addressed asap. That's quite unusual - I did a 2000 Yukon at 140K and it wasn't black, but a red-brown color. Maybe your's has done a lot of towing? Black fluid at 140K suggests it's never been serviced.

I use the well-tried process that pumps out the old fluid via the radiator top connection. I also drop the pan to inspect debris, clean the magnet, pan, and replace the filter+gasket. It's not failed me yet, and I dont know of any drawback to doing it this way, other than time and money (about 2hrs and $160 for 12qts DexronVI and a new filter). I certainly wont take any vehicle to a lube shop to have a 'transmission service' done where they just pump/flush via the dipstick. Did that once on my Dodge Caravan at 80Kmiles and the tranny broke pretty soon afterwards....

Just done our current 2011 Hoe at 75K, and concluded that wasnt too soon. 100K would have been way-over due, think I'll stick to every 50Kmiles. I posted pics of the pan condition.

I believe GM recommends a 45k mile AT service interval for "heavy" or extreme usage. I've heard that most of us fall in the "heavy" use category (lots of short trips in the city, stop and go, etc.).

Jason- if you service the transmission now and it fails in 2-3 weeks at least it won't be going out in Africa! If you perform the service now and your transmission works well for several weeks, you will probably feel more comfortable about taking your Tahoe overseas.

 

[swathdiver]

If you have access to a Tech2, it can show you the oil life of the transmission as a percentage. Just like the oil life monitor. My fluid was reddish brown at 117K and still showed 33% on the monitor. Dealer changed the fluid but I reset it to 100% at 121K it's at 97% today.