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Old 05-21-2011, 10:51 PM   #1
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Transmission flush. Good or Bad?

So today as I was having my oil changed the mechanic notifies me that I'm well over the mileage where my transmission should be drained and filled. He tries to sell it to me by saying if I bundle it with a new air filter for $25 that he'll do the tranny for $140 and give $10 off on both. Roll eyes. I ask him if by drain and fill he means flush and he says yes. I respond by saying I've heard mix reviews on flushing a tranny. He tells me he owed a TJ and that if it hasn't been done before 100,000 miles then it should ever as it would only ruin the harmony that has built up. But he insists that since I'm at 77,000 miles that I should seriously consider it. I hold off for now but I'm curious what input the forum has.

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Old 05-21-2011, 10:55 PM   #2
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i had the same choice to make at 70k miles on my 2001
I ended up going the safe way and having the pan pulled and drained, new tranny filter and the pan was washed out too.
after a new gasket and labor it cost 80 bucks.

took em an hour and a half because they had a hard time getting my skid off, lucky they charge flat rate 80 bucks so it didn't cost me =)

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Old 05-21-2011, 11:24 PM   #3
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My LJ had 58k on it when I bought it and I decided to change the fluid and filter soon after I got it. The tranny skid plate bolts presented a problem for me too but my electric DeWalt impact gun did the trick for removal and reinstallation. What a crappy design of the bolts! The trick is to spin them fast, a ratchet just won't cut it.
I've also heard horror story's of tranny flushing. I believe that a drain by dropping the pan (what a freakin mess) with a refill and new filter would be good enough but, make sure the level is correct. I filled my tranny with the recommended 4 1/2 qts and it jumped out of gear when I made a left turn (worthless Haynes manual) I added another 1 1/2-2qts and it's been fine. Apparently the fluid level needs to be checked when the Jeep is warmed up and in neutral. Warm it up and run it through all of the gears, park, neutral, reverse... The fluid won't pump with it in park.
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Old 05-21-2011, 11:53 PM   #4
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Did your trans give you signs that it need to be flushed when you did it? The mechanic told me my trans fluid was dirty whatever that means.
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Old 05-22-2011, 12:39 AM   #5
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Quote:
Originally Posted by jeepnovice
Did your trans give you signs that it need to be flushed when you did it? The mechanic told me my trans fluid was dirty whatever that means.
No, not at all. I had just bought it and wanted to do the maintenance any way. I didn't flush it, I just dropped the pan and refilled it. There are signs to look for on the tranny dip stick... A dark brown color indicates the fluid/tranny has been overheated... That's not good. The fluid is red when it goes in and should keep a red-ish, maybe some brown color when everything is working like it should be after many miles. You can also smell the fluid, sounds weird I know but it will have a burnt smell if something is wrong.
Regardless if you change it or your mechanic, ONLY use ATF +4. There are no substitutes, Chrysler trannys are very picky, and remember to check the level with it warm and in neutral.
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Old 05-22-2011, 02:01 PM   #6
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Quote:
Originally Posted by jeepnovice View Post
So today as I was having my oil changed the mechanic notifies me that I'm well over the mileage where my transmission should be drained and filled. He tries to sell it to me by saying if I bundle it with a new air filter for $25 that he'll do the tranny for $140 and give $10 off on both. Roll eyes. I ask him if by drain and fill he means flush and he says yes. I respond by saying I've heard mix reviews on flushing a tranny. He tells me he owed a TJ and that if it hasn't been done before 100,000 miles then it should ever as it would only ruin the harmony that has built up. But he insists that since I'm at 77,000 miles that I should seriously consider it. I hold off for now but I'm curious what input the forum has.
What model year TJ do you have and which transmission is in it, auto or manual?
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Old 05-22-2011, 04:49 PM   #7
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Quote:
Originally Posted by Jerry Bransford
What model year TJ do you have and which transmission is in it, auto or manual?
I have a 2003 4.0 automatic. If it matters, I just had an OME 2.5" lift with 32" tires installed. Haven't put more than 500 miles on it since.
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Old 05-22-2011, 05:15 PM   #8
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I don't know, but to me not changing the filter seems to be not doing a complete repair.

If you flush in the normal flow direction, you are just pushing all the crap deeper into the filter. So a filter that is partially blocked before the flush is still partially blocked at best.

Reverse flushing will blow some of the stuff from the filter, but not all, and anything that's heavier then the fluid can support drops back down in the pan/lines/internals.

Least is it all gets sucked back up into the already not quite clean filter, more or less putting it near the same condition it was in before. Worse, any stuff that gets deposited upstream, now has to travel back through the trans components to get to the filter, increasing the chance of something happening.

Nah, I'm replacing the filter, adding more to dilute what's in there, start it up, flipping the cooler lines to flush it out into a jug. And keep adding fluid till what I see is bright red and clean.

Least then I know I've done all I can in getting the bad stuff out, and new filter and fluid in the trans.
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Old 05-22-2011, 08:10 PM   #9
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Your Owner Manual doesn't mention transmission flushes. It just mentions fluid and filter change. That tells me something. Flushes are a money maker for the shops that do them, some transmission shops won't. May not get a filter change with a flush either, depends.
All the fluid can be changed in the transmission by running ATF+4 through it. That's not a power flush and will be okay. Normal pan drop replaces about half, which is fine.
You can also pump the fluid out through the dipstick tube to change about half of the fluid.
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Old 05-22-2011, 08:51 PM   #10
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When I went through my associates for Automotive Service we learned in auto trans class that there is no benefit to doing a flush and that it can sometimes cause more problems than it solves. On our training service floor we had a power flusher but I never used it on any of the jobs I did. A few of my classmates used it on their own personal vehicles but we never used it on customer vehicles. I would stick to a simple pan drop filter change and then fill it back up to the proper level with fresh ATF +4. I recommend the Mopar ATF +4.
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Old 05-22-2011, 11:19 PM   #11
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Ok so...
Pan Drop, Filter Change, Fill = THUMBS UP
Flush = THUMBS DOWN

Thanks for the advise.
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Old 05-23-2011, 08:59 AM   #12
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According to the transmission guy we sent all our auto tranny work to:

When you drop the pan ALWAYS replace the filter. The pan holds about 1/2 the total ATF, the rest is in the torque converter.

Dirt and the stuff sluffed off the bands and clutches has to go somewhere, most of it gets caught in the filter. Some of the finer particles too small for the filter to catch collects inside the Torque converter - centrifugal force packs it tightly. It becomes a sticky solid mass at the outermost part of the inside of the converter. But it stays there. There's more than enough room for that dirt to collect harmlessly. I've seen it - it's packed in like cement.

Flushing does not break it loose in the converter, the only way to get it out is cut it apart and clean it out - commonly what's done with a "rebuilt" converter. But it requires removal. If it did break some of it loose it could create major problems.

All flushing in place might do is get any junk collected in the lines and cooler, but since the fluid is always being forced through those it's rare for it to collect in them. It's mainly a sales gimmick.

One practice he hates is some of the "experts" (quickie lubes etc) open a line and run the engine, pumping the fluid out - supposedly to get ALL or most of the fluid out. When you do that everything runs dry for a moment - tearing things up inside. But he loved it when they did it, it made him money!

If you really want to get the majority of the fluid out, drop the pan, change the filter, fill it, run it a few minutes, the drop it again.
First time you've replaced about 50%, second time you get about 1/2 old and 1/2 new, leaving only about 1/4th old. Very seldom is it necessary.

But - If someone put motor oil in it power flushing may be in order.

We only worked on manual transmissions. Often a simple flush with Kerosene and a fill with new fluid cured shifting problems. Most shops blamed it on bad synchos, but the real cause is the small filings collecting on the synchros - flushing it properly breathed life back into many transmissions without the "rebuild."
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Old 05-23-2011, 09:27 AM   #13
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I owned and operated a fast lube for 13 years,we've done several thousand trans services.I prefer a flush and filter change to get all that old fluid out.You flush it first with more fluid than the capacity to make sure you get a total exchange ,then drop the pan and install a new filter.I guess I'm a kind of maintainence fanatic,but I still get all my stuff done that way,and I sold the business 5 years ago.If a total trans service causes problems,then something was soon going to manifest itself anyway.We also told the customer we didn't recommend a complete service if it had over 100,000 mi. and had nver been serviced.That could cause problems.Also it is the only way to save one that,s been underwater
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Old 05-23-2011, 09:33 AM   #14
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For those that want to change their automatic transmission fluid at their leisure, there are drain plug kits available, to install, such as this one: JEGS Performance Products 60175 JEGS Transmission Pan Drain Plug Kit Also, you can purchase the pan with a drain already installed (welded on). See this picture: http://dodgeforum.com/forum/dodge-ca...rain-plug.html

Furthermore, you can put a tube down the dipstick tube and pump out the old fluid (about 50%, and similar quantity to a pan drop) using a pump similar to this or a siphon bulb pump: Change Your Car's Transmission Fluid | The Family Handyman

The siphon bulb pump can be used for changing differential, manual transmission and transfer case fluid. I hook up a piece of copper tubing (brake line size) on the end to control where the suction starts from. Here's a $5.00 siphon bulb pump like I use: Amazon.com: Emergency Siphon Bulb Pump - Safe for Gasoline: Sports & Outdoors

Note: The only way to change your transmission filter is to do a pan drop.
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Old 05-23-2011, 10:56 AM   #15
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Ever wonder why the trans pan doesn't have a drain plug? That keeps the yo-yo's from just draining and filling. It forces you to take the pan down. Then the filter is right there! But there's always ways to cheat.

The "don't touch it after 100,000 miles" is promoted by rebuilders. They want the business!
Even if it has 400,000 miles or more, new fluid and a new filter cannot possibly hurt anything.

The filter acts like your kidneys, it filters out the impurities in your blood. But your kidneys self clean themselves when you piss. A trans filter can't.

But believe what you want, the needless spending really helps the economy.
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Old 05-23-2011, 12:41 PM   #16
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I think they meant no flush after 100k miles, a pan drop and filter change can be done at any time.
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Old 05-23-2011, 01:08 PM   #17
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Ever wonder why the trans pan doesn't have a drain plug? That keeps the yo-yo's from just draining and filling. It forces you to take the pan down. Then the filter is right there! But there's always ways to cheat.

The "don't touch it after 100,000 miles" is promoted by rebuilders. They want the business!
Even if it has 400,000 miles or more, new fluid and a new filter cannot possibly hurt anything.

The filter acts like your kidneys, it filters out the impurities in your blood. But your kidneys self clean themselves when you piss. A trans filter can't.

But believe what you want, the needless spending really helps the economy.
A filter change is in order any time.If you do a fluid exchange on a vehicle with 100,000 plus thats never been serviced,you run the risk of finding any potetial problems the hard way.If I buy a vehicle myself,I'm going to do a full trans service regardless,knowing the risk.But you have to be careful doing it for a customer,because they might not understand theproblems it can reveal.Also,we've had customers bring them in on a trailer,did the service,and they drove the vehicle away!The filter was stopped up so bad it wouldn't even pull off.The best policy is to keep it serviced according to mfg's reccommendations.

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