The Great Debate

[Logan Savage]

Higher mileage automatic transmission that you don't know the maintenance record of . Transmission works perfectly , fluid change / flush or not ? One school of thought says yes , another says no . I personally disassembled an auto trans. & there was gunk hiding in a lot of little nooks & cranny's . I can see the logic behind the school of thought that says don't do anything to cut this gunk loose .
There's also the school of thought that says , bunk , change that fluid and or get a flush , the trans. fluid needs changed . I can also see the logic behind this school of thought . I also have read that lubricants don't wear out , they just get dirty .
There is a man locally that has a shop at his home & makes a living rebuilding auto transmissions . He evidently is good as he has a very good reputation in this area . My father-in-law had a transmission rebuilt by him & he said the man told him it was a mistake to change the fluid in a transmission that had fairly high mileage & hadn't been serviced regularly .
A family member had a ford ranger that needed a transmission . He purchased a salvage yard transmission , installed it & it worked properly . He changed the fluid & filter & the transmission immediately went south . The salvage yard had warranted the transmission so he removed it , took it back & they gave him another one . Did the exact same thing with the 2nd transmission . It worked properly , fluid change & it immediately went south , he parked the truck after that & didn't fix it again .
Now I'm in the same boat with a jeep liberty I bought that needed an engine & I'm in the process of installing a low mileage engine in it . To mess with the automatic transmission fluid or not , that is my dilemma . The transmission is / was working properly when the jeep was parked due to engine problems . As always , input is what I'm looking for & would appreciate .

 

[ltd02]

I'd vote for the fluid change. Had >80k on mine (45rfe) when I got it and no idea of service intervals. I did all fluids right away and ****** every 20-25k since. No problem. Not a big fan of the flush on older unfamiliar trannys. Really a pan drop and filter change only changes a portion of the fluid. The Rangers have a fairly common valve body gasket issue from the 90s into the early 2000s IIRC. Not a big project to fix but may not be a good comparison here.

 

[CactusJacked]

I would probably change the fluid, but definitely not have a complete flush done. I know more than one mechanic as well who advise against changing the fluid at all on a high miles trans if it's never been done....or looks like it. With the old fluid, the clutch packs can have grit embedded in them which acts like a traction enhancer. New fluid, which is stronger in detergent than the worn out stuff, can flush the clutches clean, and chance causing slippage.

 

[Logan Savage]

Just found this article , hope it's ok to post the link .


http://articles.chicagotribune.com/2...-atf-oxidation

 

[ltd02]

Just found this article , hope it's ok to post the link .


http://articles.chicagotribune.com/2...-atf-oxidation

Gotcha on the other forum this time :gr_grin:

Here it is:

Interesting article. The key was that it's probably okay to change it if it isn't operating properly. Never really thought of this but many newer vehicles have no change interval with these synthetic fluids unless you tow therefore get it hot. I just encountered this with my 08 Sienna we purchased new. Dipstick says ATF does not require replacing. We had it flushed at 80k and I just did a fluid exchange at 185k. It has this novel thing called a drain plug so piece of cake. Only reason I did it was it was hesitating when shifting up and down during and after heavy acceleration. Fluid (full synthetic) was clearly dirty but smelled fine, just like the proper replacement fluid I used as replacement. Immediately felt better and has been fine since. I have an 11 Avenger that also states not to change the ATF (ATF+4 like the KJ) until 100k unless driven in "extreme" conditions. Anyway long story short I guess I could go along with the no change if unsure of previous intervals unless you can clearly tell the fluid is burnt or got hot or the ****** is acting up.

Kinda like if it ain't broke, don't fix it I guess.

 

[fishyx]

In my mind changing the two filters is a big deal and a routine flush does not do this. I've always done filter changes and then replace about 3 qts of Trans fluid every 10,000 miles by sucking it out of the dipstick tube. I once had a flush done on a 95 Taurus at 80,000 miles and the trans went bye-bye 3 days later.

 

[ltd02]

In my mind changing the two filters is a big deal and a routine flush does not do this. I've always done filter changes and then replace about 3 qts of Trans fluid every 10,000 miles by sucking it out of the dipstick tube. I once had a flush done on a 95 Taurus at 80,000 miles and the trans went bye-bye 3 days later.

I like the filter change too with the KJ. I guess most vehicles only have the screen and not a real filter also many don't get the heavy use of a vehicle like the KJ especially if you tow or wheel it. That's pretty brutal on the ****** as far as temperature goes too.

 

[Leeann]

Fluid and filter change, yes.
Flush, no.

 

[Hockeygoon]

In my mind changing the two filters is a big deal and a routine flush does not do this. I've always done filter changes and then replace about 3 qts of Trans fluid every 10,000 miles by sucking it out of the dipstick tube. I once had a flush done on a 95 Taurus at 80,000 miles and the trans went bye-bye 3 days later.

Where is the second filter?

I've changed a few "screens" and only once did one have much of anything in it. If the transmission is wearing like it should the wear particles should be small enough to pass through the screen. If you have "chunks" a new screen/filter isn't going to do you any good.

 

[Leeann]

Where is the second filter?

42RLEs have one filter; 45RFEs have two.

 

[M38 Bob]

Don't really have an opinion, but a very respected fellow shop owner who's specialized in transmissions for over 40 years is of the opinion that if it's been neglected for 100,000 plus and is still trouble free to leave it alone.

Most of the folks who come in my shop are fastening the barn door long after the horse has wandered off. If it's slipping, skipping shifts, limp mode, any money spent would be better applied to a rebuild.

Bob

 

[tigerKJ]

About a month ago as I went in for an oil change (live in an apartment, can't do things like that in the parking lot :thumbsdown and the shop owner pointed out the the transmission was leaking from the pan. Had the pan pulled, both filters replaced, new gasket. Then just replace the lost fluids. I have a little over a month on it now with no issues.

As a side note the drain plug was magnetic and had a few tiny bits (finer than coarse sand) on it. Not sure when the last time it was serviced.

 

[belvedere]

If you bought a vehicle that was long overdue for an oil change, would you leave the old oil indefinitely just because "it's running fine now and I don't want to risk it"? Nope, pretty sure you'd change the oil. 'Nuff said.

 

[NewerJeeper]

****** fluid is completely different from other fluids. It also doesn't just disappear like other fluids can. Over 100k miles and haven't been changed leave it alone. You can easily push something around in the ****** to make it worse. That's why places like Valvoline wont even touch your ****** if it has over 100k miles

 

[Hockeygoon]

If you bought a vehicle that was long overdue for an oil change, would you leave the old oil indefinitely just because "it's running fine now and I don't want to risk it"? Nope, pretty sure you'd change the oil. 'Nuff said.

Agreed.

I've never had a transmission fail by changing the fluid and I've only dropped a pan a couple times in my life - usually done by flush. The only ones I dropped the pan on are the ones that I could drain the TC (usually a Ford C6 and E4ODs, I don't see reason or benefit to mix dirty oil 50/50 with clean. I've had two transmission fail - a Dodge with 26K and a 1978 Ford F150 with a C4 with over 150K that failed when a shop tried to adjust the bands and instead snapped the intermediate band - then didn't tell me.


The one I was most worried about was my sister's car. She bought my mom's Taurus at 100K - never had the fluid changed. She drove it another 100K - 200,000+ miles and 10 years on a car not known for its transmission longevity in the first place. It was having some shifting issues and given the state of the fluid it didn't surprise me. Flushed it clean - oil was burnt, brown and stank horribly. She ran it another 50K and traded it off. Never had an issue. I've changed several at 100K that was their first fluid change ever - never had an issue.

 

[Hockeygoon]

****** fluid is completely different from other fluids. It also doesn't just disappear like other fluids can. Over 100k miles and haven't been changed leave it alone. You can easily push something around in the ****** to make it worse. That's why places like Valvoline wont even touch your ****** if it has over 100k miles

Actually places like that won't because people bring their car in just like my sister's neglected and abused with issues hoping a transmission oil change will help - some times it will, sometimes it won't. The owner grudgingly spends $100 getting it changed then screams bloody ****** when the issues don't go away and continue to get worse. Its like changing the oil in your engine expecting it to cure a knock, lifter noise and the smoking issue..... Shop's just don't want to deal with it.

 

[dude1116]

I was just thinking about this.

Backstory: used ****** put in about 70k miles ago. Maybe 40-50k in, the ****** would go into Limp Mode on occasion. It's escalated to some issues with the torque converter (RPMs drop SUPER low and low speeds. Think it is locking the TC too early because of lack of fluid to the TC...solenoid issue). I had the mentality to just leave it until it needed to be replaced. And here I am. I've been wondering if I should replace the fluid and filter.

 

[tigerKJ]

I've never had a transmission fail by changing the fluid and I've only dropped a pan a couple times in my life - usually done by flush.

I have had the opposite experience on 2 of my own vehicles and a few that my dad and uncles had. The makes were Chevys, Fords, and Chryslers from the 80s and 90s. Trans fluid had not been changed in 75k to 100k miles. Did complete fluid flushes and none of the transmissions lasted more than 1k. Did the transmissions have other issues? I don't know.

Decided on my next vehicle (150k miles on it) to just drop the pan, replace the filter and gasket, and add lost fluid. The trans did not fail for over 30k by the time I sold it.

So from my experience if I don't know the condition of the trans I just do the gasket, filter, and replace the fluid lost. If it was a new car with regular service, then I would get it flushed as per the maintenance schedule.

 

[belvedere]

****** fluid is completely different from other fluids.

The additives still break down due to heat and wear.

A few years ago, we bought our '05 T&C with about 75k miles. I know Chrysler says the ATF+4 doesn't need changing until 100k, but I believe in preventive maintenance, so I immediately dropped the pan, changed the filter, and filled it up with 6 qts of fresh ATF+4. I've never seen such a dramatic change in trans behavior from a fluid change. It literally felt like I had installed a shift kit: the shifts were very firm/snappy. Over the next week or so, they gradually returned to normal as the TCM relearned. That tells me that the original fluid had significantly degraded, and the TCM had gradually compensated over time.

 

[Hockeygoon]

The additives still break down due to heat and wear.

Exactly. The more the oil is stressed (city driving, towing etc...) the more heat, the more the fluid breaks down. That's why the newer cars with synthetic oils usually don't even have a recommended fluid change, its not that they run cleaner - they handle heat much better. I'm surprised that the Liberty's transmission was still on 30k intervals with synthetic, but that probably has more to do with the transmission's origins.