So I'll make it short and sweet. My dad said I should get my tranny flushed, he also said I can instead just get the filter changed. He said both shouldn't be done only one or the other. So I called jiffy lube and a mechanic there told me that with my jeep having 300,000 that the transmission fluid that I'm sure has been in there for about 5 years or so shouldn't be changed because after a while the fluid inside creates a layer of vinyl/sludge inside the trans and eventually the trans gets used to the old liquid. So my questions are should I get the transmission flushed and the filter changed or just one or the other, and is this mechanic right? Because he sounded pretty sincere but than again there's some stupid people out there thanks!

 

I would just drain the fluid and change the filter. Not flush it.

 

Just remove the drain plug on the trans pan, drain and refill. Repeat in a week or two.

Yes.. The problem is that most of the "friction material" from the clutches might be suspended in the old fluid. Once you flush it out, your clutches and such no longer grab.

How does the fluid look now?? Is it dark brown? Does the trans shift OK? Any slippage in overdrive? When shifting from 2/3?

Some old-timers suggest just a drain/fill. Dropping the pan and replacing the filter can be a bear as the fill-tube sometimes needs to be cut off. Not sure if I would have any "Jiffy" places mess with my trans.

 

Just drain & fill it. We have gone over this 1000 times. The filter is just a metal mesh screen.

 

Correct. The best automatic transmission ever built does not need gimmicky stuff!!

See post 19 of this thread.

https://www.cherokeeforum.com/f2/aw4...2/#post2927893

Use only Dex/Merc III fluid!!

 

If you have the Jiffy pukes flush the transmission, or change the fluid, they will use a Universal ATF. Not Good.


As suggested, drain the trans oil pan and refill with the amount removed using fresh Dexron III/Mercon (DEX/MERC) fluid.

 

The quick-lube places won't touch a transmission pan. They connect the trans to a machine affectionately known as "The Bilstein Wallet Flush" which sucks out the old fluid and, as mentioned, squirts in a generic, "universal" trans fluid. The Wallet Flush refers to the fact they charge a lot of money to do this.

I've been hearing the addage, "Don't change the fluid on an old trans with old fluid" since I was a kid. I'm not a transmission technician, but I put this into the category of "Urban Legend". Maybe it used to be true. Perhaps it still is. Personally, I've never seen a trans that quit working after the fluid was changed. I have seen transmissions which were not working correctly and changing the fluid resolved the problem.

So, yeah. Buy 4 quarts of the cheapest version of the CORRECT trans fluid. Remove the drain plug, drain the fluid, reinstall the drain plug and pour in the trans fluid. Run that for awhile to flush everything clean. Then buy 4 quarts of a very high quality CORRECT fluid and do it again.

 

+1 to the drain and fill. I made the mistake of having the trans in my DD grand am flushed because it was acting up... made it worse. Getting fresh fluid in is good but I suspect the flush tends to stir up junk that has naturally settled places in the trans and is doing no harm. Just my theory.

 

Maybe they didn't use the proper trans fluid?

 

My transmission fluid was BLACK and gross when I bought my XJ @ 154000 miles. I drain & filled it over a year doing it every 1500 miles or so, and now its pink and shifts well. The first few drain & fills were the most effective but I wanted to get it clean as a whistle so I never had to do it again. I used Advanced Auto's cheap Dex/Merc fluid.

 

I haven't ever heard any good things
about having a high mileage trans flushed......

Changing the oil a few times may be doing a " soft cleaning" of the parts instead of a hard cleaning with flushing, that removes all that good varnish !

 

remove trans pan.. replace your filter .. reseal and refill.. better to do the whole job .. your tranny will appreciate

 

Getting the pan off can be a challenge for many folks. The dipstick/filler tube is part of the pan. It has to be un-clamped & wiggled out etc....and all this is while the trans oil is running down your arm & into your armpit !
And the filter is just a fine mesh screen, & easy to clean....

 

Yup, dropping the pan is the only way to clean/replace filter and removing a ton of gunk from the pan and magnet. After that you can just do routine changes by either draining if your tranny has a drain plug. Or you can remove the cooler line from radiator, start engine and pump out 5 quarts then add 5 quarts of new fluid....this is the easier method if you do not have a drain plug.

 

Anything is possible. I usually do my own work but since I thought flushing was a good idea at the time I took it to a local trans shop. I would trust them more than a jiffy type joint but who knows. Funny thing is it's actually shifting better now after a couple years and probably 30k since I had it done. I think I'll leave sleeping dogs lie this time.