When to change automatic transmission fluid?

[mipa]

Hi all,

since I'm about to replace my radiator while replacing my broken water pump on my 2002 TJ, I was wondering when a complete transmission fluid flush is actually necessary. I did some reading here and the process seems not to be super simple to do at home, if I want to do a complete flush - dropping the pan, replacing the filter and gasket and pumping the old fluid out.

My TJ has about 40.000 miles and the transmission fluid is still quite clear and red (I guess? picture from dipstick attached).



I own my TJ for 6 years now and I have zero information what the previous owner did (bought it with 24.000 miles). When I read here in the forum people start talking about transmission flush are always talking about 100.000 miles plus on their Jeeps. I never of-road and my avg driving distance is 10 miles max, since I live on a small island.

I don't want to break things that are actually working fine (and don't leak) - but I also don't want to break things by skippig important maintanance

Regarding Google I've found a statement from Chrysler to replace the trans fluid every 2 years and/or 20.000 miles.. but yeah.. why not just buy a whole new Jeep every two years to support Chrysler :-D

Is there any point in only replacing the fluid that runs out when I replace the radiator with new Valvoline ATF+4 (the only option I can get here in Thailand), or is that just a half-ass move that doesn't do much and is basically a waste of money if I don't flush it all?

Seems @Chris and @Jerry Bransford are experts on this topic.. as with any topic 😬😊

Thanks,
Michael

 

[Jerry Bransford]

40,000 miles isn't unreasonable to consider changing/flushing the ATF at though it's not something that should be typically be considered urgent. But is that dirt mixed in with your ATF? If it is I'd flush the ATF with fresh ATF+4 which is not a hard job.

Flushing it at home is relatively easily done, you really only need a big bucket to catch the old ATF in and a 6' or so piece of hose with a 3/8" inner diameter and a small funnel that fits into the transmission's dipstick tube.

Disconnect the driver-side (passenger-side for US 2002 and older TJs) coolant hose from the radiator and connect the 6' hose to that radiator port then place the other end into the bucket. When you're ready, and have a helper now, start the engine. Remove the caps from that ATF+4 bottles so you won't have to stop to remove them once the process starts. Have your helper shift the transmission into Neutral which will start pumping the old ATF+4 into the bucket. At the same rate it is being pumped out, add fresh ATF+4 via the funnel you placed into the transmission's dipstick tube. It can be hard to keep up with the pump so just have your helper shift to Park to stop the pump until you can catch up, then shift back to Neutral to start it pumping again.

Once the ATF+4 is flowing bright and clear red into the bucket you are done. It will take nearly 7 quarts of ATF+4. Once you're done flushing and have reconnected the transmission cooler hose to the radiator, it's time to start the engine again.

With the engine running, shift to Neutral again and check the ATF level with its dipstick with the engine still running. Bring the ATF level up completely to the full mark with more ATF+4 as needed. And make sure the engine is always running and the transmission is always in Neutral whenever you want to check the transmission's ATF level. The dipstick will erroneously show the transmission is more full of ATF than it really is if the engine isn't running or the transmission isn't in Neutral when checking its ATF level.

Good luck with it!

Edit: Hold on. Since you're in Thailand your passenger-side and my passenger-side are on the opposite side. I'm going to post a photo to clarify which transmission coolant hose to disconnect.

And for you 2003 and newer TJ owners, the sides switched for the 42RLE transmission.

 

[mipa]

thanks a lot @Jerry Bransford especial for taking the extra time to pointing out the right hose connector - life saver as always. I have seen few posts where people used the wrong side and blew it all over their floor.

I will go ahead and order the Mopar 4295875AC Transmission Pan Gasket on amazon then and a WIX Filters - 58707 Automatic Transmission Filter (didn't find a Mopar one, and chris used that one in his post).

I know the filter kit comes with a gasket, but the Mopar one looks much better and has much better reviews - plus I always try to get Mopar for whatever.

Would be the ATP B-42 Automatic Transmission Filter Kit also fine? Since it's much cheaper... or PG Automatic Transmission Filter PT233? Since I wont use the gasket I basically only care about the best filter, but no clue if there is any difference at all. Just spotted the ACDelco Gold TF247 Automatic Transmission Fluid Filter would also ship to Thailand and seems to have the best overall reviews - plus gold sounds good?


I was also looking for a new pan with a drain plug for the future, but didn't find one that would ship to Thailand. Is there any on amazon at all? I can only use amazon or ebay for international shipping, while ebay charges 5 times the fees. I've read that it's supposedly possible to drill a hole and add a plug yourself, but that's way above my risks level, since I can't get any spare parts here if things go wrong.


My plan for now is to do the coolant system overhaul first and catch as much of the old transmission fluid when replacing the radiator and fill that back in, so I can do the transmission flush in a few weeks, when I've emotionally recovered from a hopefully successful coolant overhaul

Thanks,
Michael

 

[KennethS]

Vehicles survived for many decades with dropping the pan, changing the filter, and topping off fluid. Transmission fluid flushing is a relatively new thing and probably not really needed unless the fluid is contaminated or totally burned.

 

[Kenneth G Zinis]

40,000 miles isn't unreasonable to consider changing/flushing the ATF at though it's not something that should be typically be considered urgent. But is that dirt mixed in with your ATF? If it is I'd flush the ATF with fresh ATF+4 which is not a hard job.

Flushing it at home is relatively easily done, you really only need a big bucket to catch the old ATF in and a 6' or so piece of hose with a 3/8" inner diameter and a small funnel that fits into the transmission's dipstick tube.

Disconnect the driver-side (passenger-side for US 2002 and older TJs) coolant hose from the radiator and connect the 6' hose to that radiator port then place the other end into the bucket. When you're ready, and have a helper now, start the engine. Remove the caps from that ATF+4 bottles so you won't have to stop to remove them once the process starts. Have your helper shift the transmission into Neutral which will start pumping the old ATF+4 into the bucket. At the same rate it is being pumped out, add fresh ATF+4 via the funnel you placed into the transmission's dipstick tube. It can be hard to keep up with the pump so just have your helper shift to Park to stop the pump until you can catch up, then shift back to Neutral to start it pumping again.

Once the ATF+4 is flowing bright and clear red into the bucket you are done. It will take nearly 7 quarts of ATF+4. Once you're done flushing and have reconnected the transmission cooler hose to the radiator, it's time to start the engine again.

With the engine running, shift to Neutral again and check the ATF level with its dipstick with the engine still running. Bring the ATF level up completely to the full mark with more ATF+4 as needed. And make sure the engine is always running and the transmission is always in Neutral whenever you want to check the transmission's ATF level. The dipstick will erroneously show the transmission is more full of ATF than it really is if the engine isn't running or the transmission isn't in Neutral when checking its ATF level.

Good luck with it!

Edit: Hold on. Since you're in Thailand your passenger-side and my passenger-side are on the opposite side. I'm going to post a photo to clarify which transmission coolant hose to disconnect.

And for you 2003 and newer TJ owners, the sides switched for the 42RLE transmission.

View attachment 404800

I've got a manual, but awesome write-up Jerry!

 

[AMS417]

Vehicles survived for many decades with dropping the pan, changing the filter, and topping off fluid. Transmission fluid flushing is a relatively new thing and probably not really needed unless the fluid is contaminated or totally burned.

You get half or less out with a pan drop. Better than nothing for sure. Flush machines have been around for decades. We had one at the quick lube I worked at in 1998. I like trans pans with a drain plug. The filter rarely packs up.

 

[KennethS]

Agreed that the pan drop only drains around half, but most times that is sufficient. If the fluid is really bad then yeah complete fluid change is warranted.

 

[AMS417]

Agreed that the pan drop only drains around half, but most times that is sufficient. If the fluid is really bad then yeah complete fluid change is warranted.

We wouldn’t flush a trans with dark fluid back in the day. Most people would try to get a flush to solve problems related to neglect, then try to blame the shop for a trans failure. I just drain mine and put about 4 quarts in every couple of oil changes.

My truck has “100k” mile fluid, lol. I’ll prob change it around 50-60k. It takes a pile of synthetic so it will be spendy just for fluid.

 

[Jerry Bransford]

We wouldn’t flush a trans with dark fluid back in the day. Most people would try to get a flush to solve problems related to neglect, then try to blame the shop for a trans failure.

X2 which is exactly how the BS rumors started about transmission flushes causing transmission failures.

 

[mipa]

Disconnect the driver-side (passenger-side for US 2002 and older TJs) coolant hose from the radiator and connect the 6' hose to that radiator port then place the other end into the bucket.

do I need to plug the loose hose while flushing or does it need air for circulation?

 

[Jerry Bransford]

The loose end doesn't need to be plugged during the flushing process.

 

[mipa]

I was finally in a local garage (mistake) to have my differential fluid, transfer case fluid and transmission fluid replaced/flushed. They told me they have a machine for the transmission flush but ended up refusing to use it. They have no clue about JEEPs here anyways. So I had to force them to do the bucket trick.

I should have done everything myself at home in the first place.. lesson learned.. again.

Thing now is, that my transmission fluid looks overfilled to me.. I've driven about 7 miles (small island here) and switched thru all gears.. I then switched into neutral/idle and checked the level.. it looks like that.. and for me it's super hard to tell since its so transparent and liquid.. but I would say that's way above max?

Should I remove a quart? Or let it sit for a week and check again?

They dropped the pan.. (literally and spilled it all over the place), added 4 quarts, then drained additional 4 quarts into the bucket and added 4 quarts (without checking level in between). Afterwards they let the engine idle for 5min, checked the level and told me "ok", but they would have said anything to get rid of me I guess.

 

[BlueC]

Thing now is, that my transmission fluid looks overfilled to me.. I've driven about 7 miles (small island here) and switched thru all gears.. I then switched into neutral/idle and checked the level.. it looks like that.. and for me it's super hard to tell since its so transparent and liquid.. but I would say that's way above max?

Should I remove a quart? Or let it sit for a week and check again?

Automatic transmissions don't care if they're over full, but being under is bad. An old rule-of-thumb is to "fill her 'till she pukes", i.e. the transmission will vent off when there's too much ATF, so just make sure the fluid stays above the minimum range.

 

[TheBoogieman]

don't care if they're over full, but being under is bad. An old rule-of-thumb is to "fill her 'till she pukes",

Same rule applies when going on a first date with a fat girl. 🤫

 

[Jerry Bransford]

Thing now is, that my transmission fluid looks overfilled to me.. I've driven about 7 miles (small island here) and switched thru all gears.. I then switched into neutral/idle and checked the level.. it looks like that.. and for me it's super hard to tell since its so transparent and liquid.. but I would say that's way above max?

'Tis far better for an automatic transmission to be overfilled than underfilled. An engine can be damaged if its crankcase has too much oil in it but not so for an automatic transmission. They are routinely overfilled by at least a quart for many offroad needs like if there will be steep climbs. Mine is overfilled by at least a half-quart.

 

[mipa]

'Tis far better for an automatic transmission to be overfilled than underfilled. An engine can be damaged if its crankcase has too much oil in it but not so for an automatic transmission. They are routinely overfilled by at least a quart for many offroad needs like if there will be steep climbs.

so no reason to worry? other forum posts say the atf spilling via the transmission breath hole (forgot the right term) or otherwise could lead to a fire hazard or the possible resulting foaming could lead to bad oil coverage on the gears? would be no big deal to plug the hose on the radiator again and drain a quart back into a bottle.. I just wanna make sure I'm not to stupid to read the fluid level correctly .. but it looks overfilled, right? If you say it's fine and not risk of damage, I leave it like that.

 

[Jerry Bransford]

No there's no need to worry. And you might be checking the ATF level on the dipstick incorrectly anyway.

To check your 2002 automatic transmission's ATF level correctly, the engine MUST (!!!) be running and the transmission MUST (!!!) be in Neutral while using the dipstick. If the engine is not running or the transmission is not in Neutral while checking the ATF level the dipstick will erroneously show more ATF is there than there really is. I know you said you shifted into Neutral but was the engine running too?

P.S. I always include all the steps and emphasize them like above so others reading this in the future will see them.

 

[mipa]

engine is hot.. drove 10 miles.. engine is still running.. switching thru all gears up and down.. switching to neutral.. keep running and checking the dipstick

my guess is that the pan drop had probably only 3 quarts.. so when they added 4 back, plus flushing 4 out and adding another 4.. it resulted in 1/2 or 1 quarts too much..

 

[Jerry Bransford]

engine is hot.. drove 10 miles.. engine is still running.. switching thru all gears up and down.. switching to neutral.. keep running and checking the dipstick

my guess is that the pan drop had probably only 3 quarts.. so when they added 4 back, plus flushing 4 out and adding another 4.. it resulted in 1/2 or 1 quarts too much..

I wouldn't worry about it in the least.

 

[BlueC]

it resulted in 1/2 or 1 quarts too much..

Just for information, I had my truck's transmission rebuilt by a very reputable shop (5 year/50,000mmile warranty kind of shop) a few years ago, and they sent it home about 1qt over.