When I got my '93 4Runner, it had no service records, and 145,000 Miles on it. I drained and refilled the tranny 3 times over 3 months, didn't replace the filter, and it's still running strong 10K+ miles later. When I drained the fluid it was a darker brown color. By the last drain and fill it was only a bit darker than the new fluid.

I've also heard not to flush a tranny if you don't know the maintenance history.

Not sure what you should do, just sharing my experience.

 

If you're really worried about it... then over a period of a few months, drain a quart or so and top up with a quality Dex/Merc fluid (nothing Dexron IV or higher) and do not change the filter (yet). You want to slowly dilute the old fluid with good clean fluid. The process will avoid a sudden cleaning of things that could result in an immediate failure, will help clean things that need it, and a few bucks every week or so isn't out of most people's budget.
When you notice the old fluid on the dipstick is the nearly the same color as the new fluid you're putting in... drain and capture that fluid, change the filter, pour the fluid you drained back in and top up if necessary.

If it matters much, I had to drain the fluid on my 91 automatic and chang the torque converter so I had a few more quarts of dirty fluid getting replaced. The 91 had 190,000+ miles... not all that far from double your mileage. About 6,000 miles later and no issues.

 

Alright Abe, I think I'll go that route, I was considering that as well. Knowing that it's working out for many of you makes me feel better. 1QT at a time for a while will be alright I suppose, I know not to flush it, this hopefully will not shock it and make a mess.

Space, I just don't think it will hold much if I don't do something...

I don't have the $ for a new trans or I'd just swap it out with a 5spd now. House, student loans, car payment (starting to consider selling the LS, but I love it soooo) food, kids, all my cash is out before it get it. I have to have it last me about 2 years as is. I was not looking for this when I cam across it. It's only a toy, camping/mudding that sort of thing. But I don't want to have the trans go poof and it just sit for a year...or until I can get her fixed up. "sigh" such is life I suppose.

 

When I got my 90 the auto trans fluid was the colour of very old motor oil.

I actually kept some in a glass jar to show people and no one guessed it was trans fluid.

Anyway, I changed it twice, it works well and is a nice red colour still.

 

Would you consider this okay on an auto tranny with 240k?
it pulls strong, but my fluid is brown, not burnt. i got this truck with no maintenance records, but i think this would work for me.

 

http://www.freeasestudyguides.com/at...ion-fluid.html

If you drain the fluid and change the filter, but don't do an actual 'flush' then wouldn't the transmission basically flush itself once you put the new fluid in and trap all the crap in the new filter (you hope)? ATF is a detergent fluid, so whether you do an actual flush at the shop or not, it's still going to flush itself. The only difference is you'll still be catching all the built-up crap that's still inside once again which could get hung up somewhere else and potentially cause more problems than you had to start with. Automatic transmissions carry a LOT of pressure in the system so I believe the theory of flushing out the bad stuff and causing a leak or some other kind of problem is bull. If your transmission is being held together by hunks of sludge then you've already got problems on your hands and it's better to fix it under a controlled environment than to have it break free driving down the highway and leave you stranded. Preventative maintenance is WAY easier and cheaper than repairs. Fix it right the first time to the best of your ability. Your transmission, the rest of your truck, and your wallet will thank you and you won't have any bruises from kicking yourself in the ass over it.

 

I dont know who told this guy his transmission will fry if he did an oil change or a flush thats the best method for longetivity of your trans if that you can also put a tran. oil cooler like I did on mine, people who tell people not to change or flush there trans fluid or flush it heard it from somebody that did it but ˟˟˟˟ed up. The key for the tansmission to work properly is to change your TRANSMISSION OIL FILTER! people never do this thats why they mess up things. Also leave the truck running with the gear engage into Drive with the E-brake engaged for about 5 min do the oposite processes drain fill with new fluid and you are done simple. Unfortunately the PO never did the oil change since new (Truck had 160xx) miles on it had to be replaced when i got it. IT actually had sludge like with motor oil frekin crazy. my truck has 189,xxx on it ive done 2 trans oil and filter changes no problem. and i sometimes tow heavy ˟˟˟˟ even blew my rear airbags that go inside the coil springs and transmission is still good FYI:I got it from a used truck that had 140ish on it