I'm getting conflicting opinions with local transmission shops.

With previous vehicles (Fords) I was in the habit of changing transmission fluid every 50,000 miles, including torque converter. Easy on a Ford - pull TC drain plug, rotate 180 degrees and pull 2nd plug. TC drains completely. Do the trans and filter as usual. Every time I did this, I could feel the difference in driveability - the car loved it. It was my habit for decades.

Now with my 3rd gen 2002 3.4L T4R, apparently it's not so simple, so talked to trans shops. They want to drain and refill trans only. To my eye, that leaves over 50% old fluid in the system.

One shop told me that with a high mileage car - mine has 165,000 miles - changing the fluid now would....uh...flush "something" out of trans and it would fail sooner because of it.

What do you guys think ??

as far as breaking things loose....a lot depends on past maintance and if using a power flush.
I would drop the pn, clean it and clean or change the filter, refill, then flush.
good video on you tube of timmys
3rd gen transmission flush.
I have flushed several 3rd gens , all with over 150k on them, using the above method and have had no problems, other than finding stripped trans drain bolts...
I will be doing one soon on a tranny with 285k on it, dont know how old the tranny really is...and the fluid in it now is pretty clean and red, but gonna drop pan, do filter, and flush anyway.

If you feel like the trans has been neglected, just do a simple drain and fill every 10k miles or something for a few rounds. The A340 is fairly bulletproof (though the 01/02 trans is a bit more sensitive).

A regular drain and fill is about 1/3 the fluid - but that shouldn't be a problem.

-Charlie

I dropped my pan for the filter change when I bought my 4r (192k miles), was a waste of time as the filter was fine. Did the shade-tree flush, pump a quart out with the engine running, pour a quart in, rinse and repeat till the fluid looks better. Didn't notice any change in drivability, but I put less than 1,000 miles on before the maintenance too.

I'm planning on just doing 10k mile drain and fills for life from this point.

If the fluid doesn't look or smell bad, I doubt you're going to "flush" anything into a bad spat on the trans. Do the fluid change and never again darken the door for those shops who prefer scare-tactics to customer service. If it's nasty fluid.. still do the flush, but maybe put off that 10k mile overland trip to Patagonia and back till you put a few thousand miles on the rig to build up some confidence again.

Like many others here I just pop the trans pan plug out every other engine oil/filter change which I do at 5K intervals.
Just did this today and noted 4 1/2 quarts drained out. Refilled with fresh Valvoline Max full synthetic.
Original trans with 191K.

Now I'm really torn. I talked to an automotive shop today - highly respected local service and 2 technicians there told me - DO NOT change the fluid. It was changed when I bought the car at 65,000 miles and has 165,000 on it now.

Both said the trans would fail in hours if I do change the fluid.

I'm trying to get the car ready for a 3,600 mile round trip - 1,800 miles empty, the 2nd 1,800 towing a heavy 2 axle trailer. I think I"d best just leave it as is. They did change the oil for me today, and it has new all weather tires.

I would take that advice as a sign that shop shouldn't be trusted and run away.

There are multiple options for changing the transmission fluid. You can do a simple drain and fill, which on these transmissions really only replaces about 1/3 of the fluid. If you schedule it so you do that with your oil changes (Not necessarily every time you do an oil change, possibly every other or every third oil change depending on how frequently you perform oil changes), you'll keep your transmission fluid fresh and don't need to worry about doing a full exchange. Doing this is not going to hurt your transmission.

You can also perform a fluid exchange yourself at home following the method in this video. Doing this will not hurt your transmission.

Or you can have a shop perform a fluid exchange. If you do that, there are two types of fluid exchange machines. The new style which uses low pressure and slowly replaces the fluid. Doing this will not hurt your transmission. There is also the older style which uses higher pressure for the exchange, and can cause problems by loosening up deposits in the transmission or in the filter, and sending them through the transmission. This method of fluid exchange is what has given replacing transmission fluid such a bad reputation for causing problems.

That is a silly old wives tale. Sure some have failed but that is why the word Coincidence was created.

Not that color dictates everything but what is the condition/color of fluid now? Is is bright red and translucent? If not, just do a drain/fill. I'm on the 5th or 6th one now at 331K, plus 1 power flush at 150K, still running like a Champ!

Don't forget to use OD override to aid in keeping the trans cooler with that heavy dual axle, which might go over the official 5K tow limit. Luck.

I would avoid those shops like the plague.

If I was you, I would just drain and fill it or you can do a fluid exchange as mentioned above (check out Tim/Sean youtube channel).

I did a drain and fill on my 97 4Runner at 200K miles and in 2000 LC at 220K miles without knowing how the PO serviced it. Both are running without any transmission issues (4R is now at 216K and LC at 238K).

How many, in this thread alone, have flat out proven them wrong? And this is only a TINY minority of people who've posted in this forum who've done it without issue, and that's a tiny minority of those who've done it without issue out there in the real world.

My recommendation still stands. If the fluid in the trans doesn't look dark or smell burnt (on that f%*ing dipstick that never wants to go back in), you have ZERO to worry about. If it is burnt/dark, then would you rather take the chance it fails while away from home with badly damaged fluid in it, or while you're at home and can more easily do something about it after refreshing the fluid?

FWIW, I had THIS come out of mine and I'm still running 10k miles later:

That's an old mechanic's myth. It's easier for a customer to believe that than coincidence if they had their fluid changed and then the transmission fails.

Kinda semi-moot, I guess. I plan on installing the trans cooler before I leave and doing that will spill some and add capacity as well, that will need to be topped up. I'll count that as a partial drain/refill.

Trans fluid isn't pristine but not dark and doesn't stink, either. My feeling is that lubricating qualities are prob'ly OK, but like the idea of fresh plus fresh additives.

I'm debating adding a thermostat control on the cooler to keep temps in a good range in cooler weather....but I'm on a tight budget and can't spend $100's on it. Any suggestions would be welcome.

Also very open to the idea of manual shut off valves to cooler so I can choose when to use it. Ideas for which valves would be useful, too. I want to be very sure that anything I put on there would be temperature and fluid compatible.

With an auto transmission with an unknown service history, it's always safer to exchange the fluid slowly over time by doing drain and refills. The reason why shops suggest not to do a full flush on a high mileage transmission is because there is some truth to auto transmissions having issues after a flush. ATF has great detergent qualities to it. If the trans was abused and didn't receive regular fluid renewals, there could be a build up of sludge deposits in the trans. Now, when you drain out all the old fluid and introduce new fluid with that great detergent quality to it, the detergent works on the sludge deposits and maybe breaks free sizable chunks that end up blocking a fluid passageway somewhere in the trans like the valve body and cause big problems. So, I don't think this is an old wives tail. I believe there is truth to this issue.

So, do a drain and refill of the pan which exchanges around 4-4.5 quarts of your capacity and time it with an engine oil and filter change. At your next engine oil change, do another drain and refill of the trans pan. Finally, after yet another engine oil change, do a 3rd drain and refill of the trans pan. This will get your ATF in pretty damn good shape. After all that, I suggest you do a drain and refill of the trans pan every 10k miles or every other engine oil change if your interval for renewing your engine oil is every 5k miles.

I like doing more regular drain and refills as opposed to waiting a longer interval and doing a full flush. I've done a Blackstone Labs analysis at one of my 10k interval drain and refills and my fluid came back with a great report.

Dropping the pan and replacing the filter, which actually isn't a filter but rather a fine mesh metal strainer, isn't usually necessary. But, if the trans is having issues, definitely drop the pan to see what kind of metal debris has accumulated on the magnets and take a look at the filter media to see if it's majorly clogged at the ports.

Two local trans shops no longer do the full flush and both said they stopped because they had failures shortly after doing the complete fluid change. The added cost also factored in. I think if you neglected the trans for ~200K then flushed that it's possible enough junk could come loose to clog something up, etc. I put an additional cooler and magnafine filter after pulling the pan/filter then drain and fill every ~10K and it looks like new fluid.