Want to flush Transmission w/high miles. Good Idea?

[PuroPinchePedo]

I just bought a 2009 Tahoe LT 2wd w/120k miles. I was going to take it this week to get a oil change and figured to flush the trans while I'm at it. I've been reading a lot of people that think a trans flush, at this point with these miles, may cause more harm than good. I have no idea of the previous maintenance. Any insight you guys have about this would be appreciated! Thanks!

 

[08HoeCD]

Shops will say it's generally safe. Most on here say not to do it, do a drain & fill instead. Hard to know how much is fact vs fiction/myth.

 

[TheAutumnWind]

pan drop, filter, drain and fill definitely ok

Forced flush is probably ok, but I'd feel better about a couple of drain and fills instead.

Anyone saying to never change it IMHO is just holding on to superstition. There is no factual argument there.

 

[MichaelSE]

120k isn't what I'd call high, but I still wouldn't do a machine flush on it. I wouldn't even do one on a brand new vehicle. If you use this method, it uses your Tahoe's own transmission pump to get the old fluid out, and there is no risk of anything going wrong unless you let it run too long and let the pump dry up.

 

[Meccanoble]

These guys know what they are talking about. Just go down the list of threads and you will see many of us recently changed our fluids successfully including me at 125k miles.

 

[PuroPinchePedo]

These guys know what they are talking about. Just go down the list of threads and you will see many of us recently changed our fluids successfully including me at 125k miles.

You just did a drain and fill or a flush?

 

[Meccanoble]

Drain and fill by myself. If you look on the second or 3rd page of this section, you will see the discussion.

 

[ta07hoe]

Is it stock or lifted? Depends on the condition the trans is in. How's the fluid look and smell and how's the truck look overall. If it looks like it was used by day laborers it's probably been beaten on. If it was a soccer moms then she might have been easy on it. If it's dark and burnt smelling I wouldn't do more than a filter and refill. Atf is a detergent, if the trans is towards the end of its life then your going to get to the end of its life very quickly by flushing it. If it has been serviced regularly then you will be alright. If and when I buy a new truck/car I'd do drain and fills ever 20k to keep it consistent. Just bought mine with 160k on it and I can't decide if I want to do the filter and refill. I probably won't and I'll just put a trans in it if I still own it whenever it goes.

And just remember people on forums don't always know why they are taking about. Do you know anyone in the automotive field or that does trans work. I'm a master tech and 2 of my friends build trans's for a living and none of us know the real answer to this question lol. It really comes down to how much wear it has on it, but that's hard to tell without opening it up.

 

[PuroPinchePedo]

Is it stock or lifted? Depends on the condition the trans is in. How's the fluid look and smell and how's the truck look overall. If it looks like it was used by day laborers it's probably been beaten on. If it was a soccer moms then she might have been easy on it. If it's dark and burnt smelling I wouldn't do more than a filter and refill. Atf is a detergent, if the trans is towards the end of its life then your going to get to the end of its life very quickly by flushing it. If it has been serviced regularly then you will be alright. If and when I buy a new truck/car I'd do drain and fills ever 20k to keep it consistent. Just bought mine with 160k on it and I can't decide if I want to do the filter and refill. I probably won't and I'll just put a trans in it if I still own it whenever it goes.

It was definitely baby'd. Still had the plastic on the front and rear radio head units. Leather is in amazing condition and body is a 9/10 body and paint. I think I'll just stick to a drain, filter and fill.

 

[ta07hoe]

It was definitely baby'd. Still had the plastic on the front and rear radio head units. Leather is in amazing condition and body is a 9/10 body and paint. I think I'll just stick to a drain, filter and fill.

That would probably be fine. Do you plan to tow with it or anything. Heat is really what kills the trans. Mines been very well taken care of that's why I'm on the fence about it. what trans do you have, 6 speed or 4 speed. My friend is a world class gm tech and he said 07 6 speeds are the ones to watch out for otherwise they are all pretty reliable.

 

[PuroPinchePedo]

That would probably be fine. Do you plan to tow with it or anything. Heat is really what kills the trans. Mines been very well taken care of that's why I'm on the fence about it. what trans do you have, 6 speed or 4 speed. My friend is a world class gm tech and he said 07 6 speeds are the ones to watch out for otherwise they are all pretty reliable.

Nope. It's totally stock now. It's 2wd and I do plan to put a 5inch lift and up the tires to 33's. That's a little later down the road. For now, it's just my to and from work vehicle, nothing more. I'm not sure about the trans. I'll need to confirm.

 

[ta07hoe]

Nope. It's totally stock now. It's 2wd and I do plan to put a 5inch lift and up the tires to 33's. That's a little later down the road. For now, it's just my to and from work vehicle, nothing more. I'm not sure about the trans. I'll need to confirm.

Does it have 123d or just d and you can select gears with the push button

 

[PuroPinchePedo]

That would probably be fine. Do you plan to tow with it or anything. Heat is really what kills the trans. Mines been very well taken care of that's why I'm on the fence about it. what trans do you have, 6 speed or 4 speed. My friend is a world class gm tech and he said 07 6 speeds are the ones to watch out for otherwise they are all pretty reliable.

When I run the vin check it shows "6-speed transmission A". Just has "D" no 123.

 

[06Escalade]

There really is no such thing as a "flush", its actually an "exchange" of fluid. Old Fluid is pumped out, new fluid is sucked in using the transmission pump and cooler lines. The machine is not forcing or creating any additional pressure inside the transmission. It supplies new fluid, catches the old fluid, and has a shutoff. all it does. You can do the same exchange in your garage very simply as stated above. Much easier than dropping the pan (for me anyways, had to drop the exhaust to get the pan off).

People claim a "flush" ruined their transmission. False, the transmission was already ruined from neglect or wear. They waited too long to do anything. Then when they had the fluid exchanged it it slipped. Because the same grit and junk that was helping the worn clutch pack shift and grip was now smooth as butter. In some cases worn out clutch packs can go a little bit longer before they fail if you keep the soot grime and **** between the plates. But that is the exception, not the rule. I exchanged 4 gals of Maxlife in my garage at 125k and it shifts better than ever. its at 140k now and I'm thinking about doing it again. Not because I have to, but there is definitely some cleaning going on.

Really no point in dropping the pan for 4qts and a filter if your not changing all the fluid IMO. You will just gunk up the new filter with old fluid. If all is good and you're not taking emergency measures because of a problem do the exchange (flush), should be ok.

 

[1_8TTony]

There really is no such thing as a "flush", its actually an "exchange" of fluid. Old Fluid is pumped out, new fluid is sucked in using the transmission pump and cooler lines.

People claim a "flush" ruined their transmission. False, the transmission was already ruined from neglect or wear.

This is exactly correct.
I buy/sell vehicles every few weeks...........it's what I do every time I pick up a used car or truck with auto trans. I perform the fluid exchange myself. If if the trans slips after the fluid exchange, I replace the transmission completely.

Claiming that a "flush" ruined the trans is not exactly right.......I look at it like this, the "flush" exposed an unknown bad trans situation.

 

[rv8pilot]

Last year I acquired a 2001 Yukon XL (pictured) with 235,000 miles. The previous owner had never changed the trans fluid or anything else besides the engine oil. It was not used hard, very little towing, numerous cross-country trips and the local runs. I flushed the trans with about 3 gallons of standard fluid, ran it for a few hundred miles and flushed and replaced that with synthetic. It shifts fine, is quiet and has zero slip. There is some looseness apparent when shifting from forward to reverse but nothing alarming. Obviously it won't last forever but so far it looks like there is still a good bit of life left. The original fluid was not even that dirty and had little odor, when I dropped the pan to change the filter the bottom of the valve body was clean and there was very little crap in the bottom of the pan. Says something about synthetic fluid.

 

[ta07hoe]

you can run 50 gallons of fluid through it but the filter will still be old. I'd drop the pan change the filter. The old shit will be stuck in the old filter. Old fluid will not clog up a new filter. If it's that bad you have bigger problems. You can put the return line in a5 gallon bucket and with it running keep Filling it as it pumps out

 

[jnicks01]

Just hit a bit over 100k. Changed plugs, wires, front/rear differential fluid, drain, filter, and fill on trans, transfer case fluid, coolant, and my belts. Runs amazing afterwards. Plus the piece of mind is worth more than it costs. I was even able to get the dealer to do it for under 1K with me supplying many of the parts which were a few hundred! They must have been slow.

They really didn't have much of an opinion on whether it is a bad or good thing to completely change it. Doubt they did a total 'flush' though. My fluid was pretty clean when it came out i guess.

 

[Meccanoble]

you can run 50 gallons of fluid through it but the filter will still be old. I'd drop the pan change the filter. The old shit will be stuck in the old filter. Old fluid will not clog up a new filter. If it's that bad you have bigger problems. You can put the return line in a5 gallon bucket and with it running keep Filling it as it pumps out

Agreed and the magnet needs to be cleaned off.

 

[dross99_si]

Personally, I've always been leary of flushing and our local GM dealer said they don't recommend flushing either. We had them change the filter and fluid and it was only $149. I totally expected it to cost more..