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56K views 49 replies 21 participants last post by  cadillac_al 
#1 ·
Besides the records that came with the car (have not read yet) is it safe to flush the transmission? I did go to mygmlink.com and it said service transmission at 100k, doesent that seem a little too late? I basically want to flush it, but then I hear horror stories about it. Am I safe? :confused:

What is the best transmission flush machine that mechanics use?
 
#2 ·
Any tranny flush machine is gonna be about the same...

I think youll be safe... Every 30-50k is the safe range... Most will say you dont need to do it but IMO $100 every 50k is cheaper than buying a new tranny!!!!
 
#3 ·
Take a look at your fluid. It should be a clear color and not dark. What service did the car provide.? If there's a trailer hitch on the vehicle flush it. I did wait with mine until 105K. The garage gave me two options: drain it or pressure flush it. I had them pressure flush it and the shift from 1st to 2nd changed dramatically for the better. The garage also said that most people ignore this maintenance item. But we here at the forum know better.
 
#4 ·
I am new to this forum and until this morning, I thought it was the general consensus of the members of this board that the transmission should not be flushed but only drained with the side pan, or something to that effect, drained as well. Transmission flush is risky because it is done with cleaning solution that is used over and over again, so is contaminated, and it stirs up sediment in your transmission that is not removed and begins to work on breaking down your transmission. Many have seen transmission failure shortly after a flush. Most here it seems only recommend draining the fluid and cleaning the filters. Now, am I wrong, have I gotten the wrong impression from the majority of regular posters here?..........Tom:jawdrop:
 
#5 ·
ThomasO said:
I am new to this forum and until this morning, I thought it was the general consensus of the members of this board that the transmission should not be flushed but only drained with the side pan, or something to that effect, drained as well. Transmission flush is risky because it is done with cleaning solution that is used over and over again, so is contaminated, and it stirs up sediment in your transmission that is not removed and begins to work on breaking down your transmission. Many have seen transmission failure shortly after a flush. Most here it seems only recommend draining the fluid and cleaning the filters. Now, am I wrong, have I gotten the wrong impression from the majority of regular posters here?..........Tom:jawdrop:
By draining you only remove about 1/3 of the fluid leaving the rest of the old fluid in there. I have never heard anything bad about flushing your trans, only good things. I have a 90 Eldorado and had the trans flushed at 30,000 miles and then again at 59,000 with a filter change. Now at 71,000 my trans fluid looks bran new and I have not had any trans problems.

I also have flushed my trans and changed the filter in my Camaro twice and have not had any problems.

Get your trans flushed!

Later,
Dave
 
#6 ·
Look for posts by Geno Castellano on this forum and read them.

He's very knowledgeable.

Here's a quote:

"You have good reason to feel nauseous. There are many cases of perfectly good transmissions being damged by transmission flushes.

If it were mine, I would have the trans bottom pan dropped, the pickup screens cleaned as well as the pan, the side cover oil drained (there is a hidden drain plug for the side cover inside the bottom pan) and the tranny refilled with fresh fluid. You have no idea what went into the tranny nor what kind of fluid it was. Have it changed to minimize the chance of the flush causing you any problems.

The actual "filter" in the 4T80E trans is inside the side cover so it is not commonly serviced unless the trans is out of the car for some other reason. Just draining the side cover is sufficient but the bottom pan has to be removed to do this (to access the side cover drain plug). The 4T80E trans operates as a dry sump unit with the trans scavenge pump pulling the oil from the bottom pan to the side cover where it is stored to be picked up by the main pump. The bulk of the fluid is inside the side cover so the side cover MUST be drained with the "hidden" drain plug to effect an oil change."

Here's something from another gentleman on Caddyinfo.com:

"You are just the next person in the litany of people who have had their trans "flushed" in good faith only ot have the trans fail catostropically within a few weeks. It happens a lot. That is why I steadfastly recommend to people to NEVER have a transmission "flushed" at a shop or quickie oil change. You probably got some debris into the trans from dirty oil from the flushing equipment, debris in a line from the equipment from the last trans flushed, etc...or it stirred up some sort of debris that was in your trans that got in a valve and stuck it. Very very common to have happen if you start stirring things up. Sorry it happened to you but it is very common with flushes. They are nothing but moneymakers for oil change places...and transmission shops a few weeks later...."

"Think about the flush... most everyone ignores their trans until it starts to slip or act up...so...they rush to the oil change place to have the trans "flushed" in the fervent hope that it will cure the problem. So, there is a very high likelyhood that the last trans that was hooked to that flush equipment was failing and generating debris...which you may have in your trans now. Would you get a blood transfusion from an unknown source...???"

"Do NOT let the place power flush the trans or hook it up to any sort of flush machine or anything. Lots of bad news there. Bottom line, you might end up with all the trash and debris from the last trans hooked to that machine. Do not be tempted."

"Imagine the concept of an automatic transmission with many many hydraulic valves and passages that are toleranced to the millionth of an inch....and someone proposes "back flushing" the filter and any debris it might contain back into the trans.....ack....run screaming from that shop. Sure bet for disaster. Just stirring up any fines or particulates or metal particles inside the trans that could get them into the various valves and such gives me the creeps. What a concept. FORGET IT."
 
#7 ·
Never, ever flush a transmission. There is no "safe" way to flush a tranny unless you own the flush machine and control it yourself. Flushing a tranny has several pitfalls.

The most obviuos is that the last vehicle hooked up to that flushing machine probably was on it's last leg and was generating tons of debris. Most owners, when the tranny starts to act up, rush to get a "flush" in the fervent hope that it will cure the problem. So flush machines, by definition, see the worst of the worst. If the lines aren't cleaned, hooked up improperly, oil is reused or recycled, etcetera - then you are screwed as your tranny gets the dose of debris from the last job. No matter how good the intentions of the shop, one simple mistake and your tranny gets the debris.

Flushing is supposed to negate the need for removing the pan, cleaning the debris and replacing the filter. Nonsense. There is considerable debris coating the inside of the transmission pan with miles as anyone who has done this can attest. That is part of the maintenance, removing the pan, cleaning the screens and replacing the filter and cleaning the pan.

All that debris in the pan is laying around in areas where there is little oil flow by definition. It tends to settle in the areas where the oil is quiet and just lies there not hurting anything. Until the "flush" stirs it up and circulates it thru the tranny. What a concept.

Reverse flush? What logic makes anyone think that it is a good idea to reverse the oil flow path in a reverse flush and flush sediment and debris into areas that are normally protected by filters, etcetera? Bad idea. Period. No other way to describe it.

"Transmission flush" machines are money makers for the shops and dealerships because they are quick and easy and they can actually charge more money for it under the guise of it being "better" for the tranny when it is really a detriment.

Read the factory service manuals and point out the place where a transmission "flush" is recommended. So what if all the oil cannot be removed. A "flush" doesn't remove it all either.

If you really really want to replace as much oil as possible in the transmission, drain the pan, service it by removing, cleaning and changing the filter and reassemble. Refill the transmission with fresh fluid. Disconnect one of the cooler lines at the radiator, put it into a bucket and start the engine. Let the trans oil pump purge the old oil into the bucket so that nothing is subjected to abnormal oil flow. Start pouring oil into the trans to keep it full while the idling engine/tranny oil pump purges the fluid through the system. Easy and quick and gets ALL the fluid out and eliminates any risk of hooking up to a "flush machine".

I know this is about 4.1/4.5/4.9 engines but be aware that on the Northstar engines/4T80E transmissions there is a hidden drain plug for the tranny side cover that requires that the bottom pan be removed to drain the side cover oil storage area. The idea of flushing a 4T80E is even more ludicrous than a 4T60 trans for this reason.

The 4T60 and 4T80 transmissions are similar in that both store oil in the side cover but they do it differently. The 4T60 trans with the 4.x engines stores oil in the side cover only when hot. There is a bimetal thermostatic valve that closes causing side cover oil to be trapped behind a wier or dam. So, change the oil in a 4T60 trans when it is cold to get the most oil out. The 4T80 transmission is a dry sump unit that always stores it's oil in the side cover. There is a scavenge pump that scavenges the oil from the bottom pan to the side cover all the time. That is why there is a hidden drain plug underneath the bottom pan to drain the side cover when the pan is off for service.

People. Stop flushing your trannies! Normal transmission maintenance is a good idea. Drop the bottom pan, change the filter and clean everything up and refill the tranny with fresh fluid. Do the cooler line/bucket purge if you are really set on changing all the fluid but don't hook your tranny up to a flush machine!

Really now, would you get a blood transfusion from an unknown source that is reusing needles? It's about the same thing if you think about it. A flush will do absolutly nothing more than a good drain and refill will accomplish and potentially a lot of harm. Don't take the risk. Just because some have had good experiences (or the lack of a bad experience) with a flush doesn't mean they'll all be that way.
 
#8 ·
What kind of proof do you have of transmissions failing after a flush? Do you have numbers? What are your sources? Everyone I know, including me, who has had their trans flushed multiple times has NEVER had a problem and all of us still have perfectly functioning transmissions. Are you an ASE certified mechanic? Did you do trans flushes for a living and then disassemble trans after to see the effects? Did you work in a trans shop and rebuild trans that had been flushed and ruined?

Also, you mention in your post that many transmissions are already failing, get the flush, and then fail. So with that theory, the transmission was already doomed to begin with! RIGHT??? It's like not changing your oil for 40,000 miles, then changing it and blowing your engine. Was it the oil change that blew your engine? NO! It was the neglect for 40,000 miles!

I have read that flushing your trans when you have high mileage like 100,000 may be bad, it does something, not sure exactly what, I forgot! But not flushing it will definately result in a problem vs possibly a problem by flushing it. I read that in the Chicago Tribune in the Q and A auto section in Sunday's edition. So does this ASE certified mechanic/editor with a number of vast resources at his disposal not know what he's talking about? From what you're saying, he doesn't.

Why don't we take a vote here! How many of us have had our trans flushed without problems in proper intervals? How many have had problems in proper intervals/improper intervals?

90 Cadillac Eldorado
Trans Flush at 30,000 Miles and again with filter replaced at 59,000 Miles.

99 Camaro Z28
Trans Flush at 25,000 Miles and again with filter replaced at 45,000 Miles.

My past 97 Camaro Z28
Trans Flushed at 30,000

All cars had no problems! How bout you guys? Post your good/bad experiences.

Another thing to point out. I bought my caddy with 24,000 miles in April of 02. By the time I had the fluid flushed at 30,000 miles the fluid/trans/filter was 12 years old!!! No problems after the flush.


Later,
Dave
 
#10 ·
Thats why you go to a reputible shop, and if necessary supply your own fluid... They may use recycled fluid, but not if you give them good stuff...

Ive never heard of places using recycled fluid. I would recommend going to a dealer, or some place of that nature.. Maybe cheapo jiffy lube-equivalent places wouldnt be the best place...

But, I will have a VERY VERY hard time believeing that a flush could really destroy a good tranny, especially one well maintained... ON the infiniti forums, there have been ones that go 100k with no flush, they do 2, a pan drop, filter change and it shifts as new.....

I will be doing a tranny flush this summer, and I hope it will make things a little better (a slow shift)...
 
#12 ·
I like that... Its probably best to drop the pan and clean it, and replace the filter than nothing.. its also best to do this before a flush anyway!

This is what I plan on doing to my car!
 
#13 ·
99Z. Read my post again carefully. I didn't say the tranny that came in on it's last leg would be ruined by the flush. Just read carefully. I said that transmissions that are on their last leg are often flushed in the hope that the flush will cure the problem. That just about guarantees that the trans flushing equipement is going to injest a lot of debris from failing transmissions. That debris could end up in the next transmission that's flushed on that equipment- thus ruining it. That is what the post clearly says. Of course if a tranny comes in on it's last leg the flush did not damage it further but it very well could damage the next transmission that's flushed on that equipement if the lines are not cleaned carefully and hooked up correctly...

No one knows what kind of fluid is being used in the flush equipment. That is the point. For a "flush" to be effective there would have to be a lot of fluid pumped through the tranny. Guys that do the purge method described often go through several gallons of fluid to get the clear, new fluid coming out. Do you really think that the flush equipment is going through that much brand new high quality fluid on each flush? That would be the day...

No, I don't work on transmissions for a living nor do I run flushes. But, I've been involved in the automotive repair industry for several years and have seen a lot of ways that people can fail transmissions - and flushing a perfectly good tranny is a high risk endeavor. I clearly said that not all flushes will result in failure - but that there are significant risks involved in having a tranny flushed. If you want to take them fine, but understand the risks and don't ignore them.

Elwesso. If you can't understand how a tranny flush can ruin a perfectly good tranny then you need to reread my post carefully. You don't believe that stirring up debris in the transmission and flowing it backwards through the valves and orifices in the valve body can cause problems? You don't believe that you could get debris from the previous (failing) transmission that was hooked to the flushing equipment into your tranny causing it to fail? What part don't you understand?

Look at the flushing business logically. The tranny shops and quickie oil change places are out to make money - not look after your car, your engine or your wallet. They will do what it takes to make money. They obviously make more money off of flushes than dropping the pan and doing the service correctly. If they didn't they would drop the pan. This alone should give you a clue. There is a perfectly good reason that flushing a tranny is not in the service manual as the way to service the transmission.

All those transmissions flushes - did you change the filter and such or did you buy into the logic of the flushes that the flush back flows all the stuff out of the filter negating the need to change it? That is some logic! Back flow the crud out of the filter and through the tranny so the flush machine can catch it.:rolleyes:

I have personally communicated with 3 owners of Cadillacs over the last few months that took perfectly good transmissions in for a routine "flush" and experienced a transmission failure within the next 5 thousand miles. Not proof, no, but good enough, along with the engineering logic and analysis provided for "me" to never have a transmission flushed. If you disbelieve this do some searches on the net.
 
#14 ·
Msilva954 said:
I think what I am going to do is drop the pan and so forth, but I will also call good transmission shops and the dealer to see if they flush using new fluid or what. How does that sound?

It sounds like a complete waste of time. Let me save you the time. Of course they are going to say the fluid is of the highest quality and is new. Of course they will say this. Why bother to ask? Do you think anyone would use their flushing equipment if they said otherwise? Unscrupulous shops will recycle the oil, use substandard bulk oil, do whatever it takes to make more money. Plain and simple.

Back to basics. The flushing makes money for them. If it didn't, they would do the service correctly. Ask yourself how they are making more money with the tranny flush and the answer should be obvious to you as to what you want done to your transmission.

Get your tranny serviced correctly by dropping the bottom pan, servicing the filters and screens, cleaning the pan of debris and filling with new, quality fluid from known containers. Not an unknown 55 gallon drum. You'll thank me in the long run.:)
 
#15 ·
Guess it doesent sound that great after all :bonkers:

Is droping the pan and doing it that way easy enough to do it in your garage or should you have a mechanic do it? My father did work on cars in his 20's, so he has somewhat knowledge when it comes to cars.

If I do go that route what is the best fluid and filter to use? OEM?
 
#16 ·
Msilva954 said:
Guess it doesent sound that great after all :bonkers:

Is droping the pan and doing it that way easy enough to do it in your garage or should you have a mechanic do it? My father did work on cars in his 20's, so he has somewhat knowledge when it comes to cars.

If I do go that route what is the best fluid and filter to use? OEM?
The OEM filter (24206433 according to GMPartsDirect) is only about $11. GM list is about $18.

I don't know if that includes the gasket (24204624) which they carry at $21.30, (lists at $37.38).

It isn't a particularly difficult job. About the worst part is having to remove all those bolts with your hands up in the air while on your back. I've done it quite a few times, and I still always end up with trans fluid running down my arm. The only cautions I would have are to avoid letting the pan hang on one or two bolts once you've cracked the seal open as the weight of the fluid can bend the pan flange. Also, be careful with torquing the bolts on reassembly. The trans case is aluminum and the torque specs are pretty light in the manual, if I recall. Don't want to strip the threads. I always use a torque wrench for the pan bolts, but I'm a torque-wrench-aholic.
 
#17 ·
Msilva954 said:
Guess it doesent sound that great after all :bonkers:

Is droping the pan and doing it that way easy enough to do it in your garage or should you have a mechanic do it? My father did work on cars in his 20's, so he has somewhat knowledge when it comes to cars.

If I do go that route what is the best fluid and filter to use? OEM?

It is not a bad job at all. Just get a large drain pan so that you can loosen the pan without the draining oil spilling onto the floor. Other than that it is about as straightforward a job as there is.
 
#18 ·
I had my transmission flushed at 36,000 miles. It was operating fine and I thought I was doing some good preventive maintenance. By the time the car had 42,000 miles on it the transmission was burnt to a crisp. Can I absolutely prove it was the flush - no. However, I won't do that again.
 
#19 ·
Geno, you had 3 people who's transmissions failed within' 5,000 miles of the flush. Can you confirm that the failure was from the flush? What proof do you have? How many people don't have problems? If a customer has a good experience with a company/service they will tell only 1 or 2 people. An unsatisfied customer will tell 20 people. That is a fact! It has been in many of my textbooks in school. With that said you're not going to hear of many success stories when it comes to trans flushes but anyone who thinks the flush may have caused a problem is going to be vocal about it. How many millions get their transmissions flushed a year, and you know of only 3 that were damaged? And like I said before, what proof do you have that they were damaged by the flush? Pure speculation isn't a fact. How many miles were on these transmissions, how were they previously serviced, how old were the vehicle? My buddy has an 03 Dodge Ram which he just got a new trans for at 12,000 miles. While he hasn't gotten his trans flushed yet if he had just gotten it flushed and then 2,000 miles later it blew, you would blame it on the flush, when it had nothing to do with it. Get my point?

I also would never take my car to a Jiffy Lube to have a flush performed. They do enough damage just changing the oil, let alone something more complicated like a trans flush. Now having a trans damaged by someone that is unskilled or unknowledgable at Jiffy Lube is probably more of a fact than opinion, but without stats and figures how can anyone really prove that? You can't.

Yesterday I was talking to the two owners of Power House Performance, where I take my Camaro. I asked them about trans flushing and brought up your points. They said they've never heard anything bad and get their transmissions flushed too. Although, as I have already done, they do suggest changing the filter. But again, that's opinion as far as I'm concerned! It makes me sleep easier at night! They are also not trying to sell me on a trans flush because they do not have a flush machine at their shop. They do performance mods, not routine maintenance such as flushes.

I just find it hard to believe so many transmissions are failing due to a flush and not some other explanation.

One of my friends use to work at a trans shop! I'm going to call him today and see what he has to say. He doesn't work there anymore so he has no reason to give me false info, plus he's my friend!

I'm sure if done right a trans flush is beneficial and if done wrong it can be harmful! Although, that goes for anything.

Who knows?

Later,
Dave
 
#20 ·
99Zee28 said:
I'm sure if done right a trans flush is beneficial and if done wrong it can be harmful! Although, that goes for anything.

Who knows?

Later,
Dave
I certainly agree on the statement above. I'm sure that a tranny flush could be a positive thing in certain circumstances. But, there are a number of engineering arguments against the practice. Read my post. Those are my opinions, yes, but they are also the opinions of engineers that design and manufacture the transmissions. An aquaintance of mine worked with the Chief Engineer of the 4T80E and mentioned transmission flushing to him. He just rolled his eyes, laughed and walked away.

Can I prove that anyone's transmission died due to a flush? No. But can you prove that they didn't? No. The evidence is just circumstantial, but there are a lot of cases mentioned where a tranny that was operating fine was flushed and died shortly thereafter.

There are sound engineering reasons not to flush the tranny due to the debris, back flowing fluid, unscrupulous flush operators, etcetera. Are all transmission flushes bad? No! Are some of them bad? Yes. See above. How do you know which are the bad ones and which are the good ones? You can't tell. How do you avoid the "bad" flushes? Never flush the tranny. It's as simple as that. That's the low risk approach. Service it correctly and you wont be exposed to the potential damaging factors of a flush. That's all I'm saying.
 
#21 ·
I don't go to Jiffy lube type places, so I didn't really know that such a thing as a transmission flush existed until recently.

I can't understand why anyone would do it without changing the filter and cleaning the pan, both from a preventative maintenance standpoint (examining the pan for debris) and from the idea that if the trans fluid is so bad it needs to be flushed, then certainly the filter is partially clogged - what good is clean fluid if it can't get through the filter?.

If you're worried about getting all the fluid out, then the method mentioned above (disconnecting the lines and letting the transmission cycle new fluid into itself) seems far safer than hooking up any sort of external machine and more effective since the trans pump will then be moving as will the torque converter, which doesn't appear to be the case with a flushing machine.

The only way a flush can be "better" than that is to use a higher pressure, or an additive. I don't know that I'd want to send higher-than-designed pressure through my transmission and fluid additives (mentioned by a lot of the flushing machine companies - do a google search) are specifically warned against in the service manual.

About the only reason I could see flushing anything transmission-related is the cooler, as I believe there's a process for it outlined in the service manual. However, that is done by disconnecting the cooler from the trans and flushing it separately (and backwards, if memory serves). If debris can accumulate in the cooler, I certainly wouldn't want to remove them by forcing them through the rest of the transmission via a flush.

I guess if performed correctly, it can't do any harm, but I'm not sure that's the point. If your goal is to get clean fluid in, there's a standard, zero-risk procedure - drop the pan and replace the filter. If you really want all the fluid, then there's a zero-risk procedure - disconnect the lines to the cooler and cycle fresh fluid in. If you need to flush the cooler and lines there's a factory procedure, again with minimal risk. Trying to accomplish any of those things with the flush and its inherent risk seems foolish. Trying to do more than that - i.e. "clean" or blast out the debris, or worse yet, cycle them backwards through the system - sounds dangerous and potentially goes directly against the manufacturer recommendation.

One other thing that hasn't been mentioned is that there are different transmission fluids out there. The biggie is Chrysler's which is not compatible with everyone else's. Audi and VW also have a different one (dyed yellow instead of red) on some of their transaxles. It would be interesting to see what the procedure is in these shops to ensure that their flusher lines are completely purged of fluid every time they switch over, or if they just use some "supposedly universal" fluid in every trans they flush.
 
#23 ·
Msilva954 said:
This may sound dumb but keep in mind this is my first car.... Is there a product supposed to be used that cleans the pan really good or do you just go in the back yard and hose it down??? :hmm:
The pan itself will typically have a thin layer black powdery residue (suspended in the remaining oil) that usually wipes off with a cloth. There's a magnet in there that collects a lot of filings. I ususally use rags to pull that off - don't forget to put the magnet back in.

If you have anything other than a little bit of fine powder in there (like metal chips), I'd suggest posting what you find before bolting it back together.
 
#24 ·
Just use some carb cleaner or something along those lines.. Hell go get some seafoam and slosh it around in there, and wipe clean with a towel...
 
#25 ·
Geno- lets assume this: If a tranny flush machine was perfectly clean, with brand new fluid, and you were flushing it regularly (IE not back-flushing), wouldnt you say that this would be a safe way to do it....???
 
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