Dealerships and Transmission Flush

[GreenMachine]

Asked if they do a transmission filter and fluid change.

He said they would change the fluid with flush machine. I said that flushes have been known to be bad and to clog up trannys.

To this he replied that the passages inside the transmission are so small that keeping the unit closed, and simply "changing" or "flushing" rather than opening the unit is much better since no containments can get in the system. He said a proper flush is the way to go and that BACK FLUSHING is what is known to destroy trannys.

around $180 if I want that service done.

[KHE]

Back flushing???? You've got to be kidding! It would be interesting to hear his explanation on why stirring up the crud/clutch material in the low flow area (in the pan where it is harmless) and pushing fluid the opposite direction, defeating the filters and causing debris to enter areas it would otherwise never see is the "Proper" way of changing the fluid.... Also ask him where in the GM recommended procedures it states to FLUSH a transmission.

[mmarinov]

Back flushing???? You've got to be kidding! It would be interesting to hear his explanation on why stirring up the crud/clutch material in the low flow area (in the pan where it is harmless) and pushing fluid the opposite direction, defeating the filters and causing debris to enter areas it would otherwise never see is the "Proper" way of changing the fluid.... Also ask him where in the GM recommended procedures it states to FLUSH a transmission.

I think the tech was saying that backflushing was the harmful method, not the "normal" flush he would perform.

I'm in the market for getting my ATF changed but I'm not getting it flushed anywhere. I'm going to a tranny shop where surely they would know how to drop pan/change gaskets if I requested it.

Mark

[MAC]

He said that BACK FLUSHING was not good--correct?

Anyway, I'm about to service my trans and I will do it manually by removing the pan, clean the screen/filter and change fluid by disconnecting upper radiator trans line, starting engine and having the trans pump do the work and fill with new fluid as it's being pumped out.

I have one question: Is filling with synthetic trans fluid worth the money--it's about $6 per quart?

[GreenMachine]

yeah back flush is bad he said

[Ed Hall]

To this he replied that the passages inside the transmission are so small that keeping the unit closed, and simply "changing" or "flushing" rather than opening the unit is much better since no containments can get in the system. He said a proper flush is the way to go and that BACK FLUSHING is what is known to destroy trannys.

around $180 if I want that service done.

He's worried about contaminants getting into the system if the pan is dropped??? I don't believe it and would not have my transmission flushed.

[epricedright]

edited

[epricedright]

Back flushing???? You've got to be kidding! It would be interesting to hear his explanation on why stirring up the crud/clutch material in the low flow area (in the pan where it is harmless) and pushing fluid the opposite direction, defeating the filters and causing debris to enter areas it would otherwise never see is the "Proper" way of changing the fluid.... Also ask him where in the GM recommended procedures it states to FLUSH a transmission.

I think the tech was saying that backflushing was the harmful method, not the "normal" flush he would perform.

I'm in the market for getting my ATF changed but I'm not getting it flushed anywhere. I'm going to a tranny shop where surely they would know how to drop pan/change gaskets if I requested it.

Mark

All the Caddy dealers in my area wanted to flush as well...NOT. I would be a little worried to take it to a tranny shop...thinking sabotage. They know TOO much about trannies.

[PAUL T]

Here is what our old Guru (A GM powertrain engineer) had to say about it.

"Transmission Flushing - Good or bad?

Never, ever flush a transmission. There is no "safe" way to flush a transmission unless you own the flush machine and control it yourself.

Flushing a transmission has several pitfalls...

The most obvious 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 transmission 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, etc....then you are screwed as your transmission gets the dose of debris from the last transmission . No matter how good the intentions of the shop, one simple mistake and your transmission gets the debris.

Flushing is supposed to negate the need for removing the pan, cleaning the debris and replacing the filter... BS. 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 transmission. 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, etc...???? Stupid 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 transmission... when it is really a detriment.... suckers are born every day...

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/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 transmission oil pump purge the old oil into the bucket so that nothing is subjected to abnormal oil flow. Start pouring oil into the transmission to keep it full while the idling engine/transmission oil pump purges the fluid thru 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 transmission 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 transmission 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 transmission 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 weir or dam. So, change the oil in a 4T60 transmission 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.

FORGET THE IDEA OF FLUSHING YOUR TRANSMISSIONS. Normal transmission maintenance is a good idea. Drop the bottom pan, change the filter and clean everything up and refill the transmission with fresh fluid. Do the cooler line/bucket purge if you are really fastidious about changing all the fluid... but... DO NOT hook your transmission up to a flush machine.

Really now, would you get a blood transfusion from an unknown source that is reusing needles... about the same thing if you think about it. A flush will do absolutely nothing more than a good drain and refill will accomplish... and potentially a lot of harm. Do not take the risk. Just because some have had good experiences (or the lack of a bad experience) with a flush does NOT mean that they will always go good."

[clarkz71]

I have one question: Is filling with synthetic trans fluid worth the money--it's about $6 per quart?

I used the latest GM fluid, Dexron VI. It made a big difference in shift quality. It's around $10 a gal ($2.50 qt) from GM parts direct. GM is the only place to get it for now. Part # 88861045. GM says it superceeds all previous Dexron fluids and is compatible with all Hydromatic transmissions. I also did the top line purge method.

[GreenMachine]

I was explaining to him that I did have the FSM and it describes dropping the pan and changing the screens. He said that these transmission are pretty good and just a fluid flush to remove all the old and place in all new fluid is the way to go. Said something about a magnet in the pan too.

Anyway this was the parts department guy and he really seemed to know what he was talking about, but then again if he is trained by GM, just like all the techs, this is how you service a trans, than maybe to him it is the correct procedure.

The Factory Serice Manual doesn't mention anything about "flushing" except for section 7-114 "Transmission Cooler Flushing". It describes a procedure using "J 35944-A" to flush the cooler. The manual describes this as a "Transmission Oil Cooler and Line Flushing Kit".

It goes on to say to disconnect the return line and check for proper flow and to do this procedure anytime the tranny is removed for service and is essential for "SRTA" installation, whenever the fluid has possibly been contaminated, major overhaul, pump or torque converter replacement.

Would this be the machine they use? I don't know but that is the only mention of "flushing" in the service manual.

EDIT: I started righting this post before the "Guru" repost (couldn't stop fanning threw the service manual looking at all the neat things in there ). I know this subject has been beat to death but is always good to get new sides to the argument, the tech said opening the transmission could contaminate it and the small passage could get clogged up by something as simple as human hair (thats when he started to lose me). I'll see what procedure my trusted shop will do, I know if I tell them to drop the pan, replace the screens, gasket, and do it like it says in the manual they will.

[Ranger]

Contamination by opening the unit is just their way of justifying doing what you do not want them to do.

I am sure that flushing is much faster than dropping the pan and time is money. That's why they all do it now.

[OynxSTS]

I was explaining to him that I did have the FSM and it describes dropping the pan and changing the screens. He said that these transmission are pretty good and just a fluid flush to remove all the old and place in all new fluid is the way to go. Said something about a magnet in the pan too.

Anyway this was the parts department guy and he really seemed to know what he was talking about, but then again if he is trained by GM, just like all the techs, this is how you service a trans, than maybe to him it is the correct procedure.

Everyone seems to forget this fundamental truth. Dealers are NOT GM. Dealers are independent business people who are in business to make money. FULL STOP.

And like any "small" business some are a lot more honest then others...

The easiest, fastest and IMO favourite way for dealers to make money is to convince you to perform service on your car that is not required.

I'd ask the tech, who mentioned the magnet... "what's it there for? and how will flushing remove all of the "crud" that collects around the magnet..." The answer to this rhetorical question is that it won't.

Drain, replace screens, replace the gasket and fill.

This is the correct and ONLY way to do this.

[MAC]

I used the latest GM fluid, Dexron VI. It made a big difference in shift quality. It's around $10 a gal ($2.50 qt) from GM parts direct. GM is the only place to get it for now. Part # 88861045. GM says it superceeds all previous Dexron fluids and is compatible with all Hydromatic transmissions. I also did the top line purge method.

Thanks Clark...I'll try it. I should only need a couple of gallons since the trans is wet.

[JimD]

....

Drain, replace screens, replace the gasket and fill.

This is the correct and ONLY way to do this.

Some of us disagree.

It is not necessary to open the open the pan or replace the screen or even get your hands dirty.

[KHE]

I was explaining to him that I did have the FSM and it describes dropping the pan and changing the screens. He said that these transmission are pretty good and just a fluid flush to remove all the old and place in all new fluid is the way to go. Said something about a magnet in the pan too.

Anyway this was the parts department guy and he really seemed to know what he was talking about, but then again if he is trained by GM, just like all the techs, this is how you service a trans, than maybe to him it is the correct procedure.

The Factory Serice Manual doesn't mention anything about "flushing" except for section 7-114 "Transmission Cooler Flushing". It describes a procedure using "J 35944-A" to flush the cooler. The manual describes this as a "Transmission Oil Cooler and Line Flushing Kit".

It goes on to say to disconnect the return line and check for proper flow and to do this procedure anytime the tranny is removed for service and is essential for "SRTA" installation, whenever the fluid has possibly been contaminated, major overhaul, pump or torque converter replacement.

Would this be the machine they use? I don't know but that is the only mention of "flushing" in the service manual.

EDIT: I started righting this post before the "Guru" repost (couldn't stop fanning threw the service manual looking at all the neat things in there ). I know this subject has been beat to death but is always good to get new sides to the argument, the tech said opening the transmission could contaminate it and the small passage could get clogged up by something as simple as human hair (thats when he started to lose me). I'll see what procedure my trusted shop will do, I know if I tell them to drop the pan, replace the screens, gasket, and do it like it says in the manual they will.

The flush gun the factory service manual mentions is for cleaning the trans. cooler lines and cooler in the event the trans is removed from the vehicle. It is not the same piece of equipment that the dealer parts guy wants to use on your car.

Before dropping the pan, clean the exterior surfaces to remove any dirt/road grime, etc. and then there won't be a chance of dirt getting into the trans. Also, once the pan is removed, thoroughly clean it - inside and out and install a new pan gasket from GM. Do not use an aftermarket gasket as they do not have the steel bushings and the pan will be damaged when the bolts are torqued to spec. Also, there are no passages in the trans that are small enough to be clogged by a hair - just keep your head out of the valve body and you'll be all set... I've changed the trans. fluid in all my cars over the years and have never had a problem.

The GM trans. kit contains the pan gasket, screens, and screen seals and it CHEAPER than just buying the pan gasket alone.

[Poobah]

My transmission needs a fluid change (one of the remaining service items left on my list after buying the car). I stopped by my local independent transmission shop to touch base, find out how soon I could get an appointment, ask how much it costs, and how long it takes. I've done business with this guy in the past, he's a straight shooter and I trust him. You might be interested in what he told me.

First, he said the 4T80-E is the best transmission GM ever built. He said they have electrical problems once in a while but he's only had to completely rebuild 3 of them over the years.

Since my transmission has 83,000 miles on it he said it would be best to drop the pan, drain it, replace the filter, clean the magnet, and re-fill it. I suggested checking the little piles of clutch debris in the pan to which he responded, "There won't be any, its a 4T80-E."

He then told me that on transmissions with over 100,000 miles, he recommends not changing the fluid and just leaving them alone. He said that fresh transmission fluid is thinner than old fluid and that when older transmissions are re-filled with new fluid, they are quite prone to leak. He said, "When that happens my customers come back and blame me for the leaks."

He said he charges $100 for the complete service, it takes about an hour to an hour and a half to do, and if I make an appointment, he can do the work while I wait.

[epricedright]

That sounds good Poobah. I paid $119 and that included the OEM GM trans kit. Had it done w/ 90K on the clock and NO leaks...now I need to find some wood to knock on.

[Ranger]

I have changed several when they hit 100K and never had a problem. Personally, I would not let it go beyond 100K for fear of a leak.

[MAC]

He then told me that on transmissions with over 100,000 miles, he recommends not changing the fluid and just leaving them alone. He said that fresh transmission fluid is thinner than old fluid and that when older transmissions are re-filled with new fluid, they are quite prone to leak.

I take it that's internal leaking which could cause trans failure?

[clarkz71]

Thanks Clark...I'll try it. I should only need a couple of gallons since the trans is wet.

Well, if you want to replace all the fluid via top line into bucket method you'll need 4 gal's.

The capacity of the 4T80E is:

Dry: 15 qts

Overhaul 12.6 qts

Pan & side cover 8 qts

I know it's not dry, but replacing "all" the fluid requires 4 gallons. How I did it is I dropped the pan and drained the side cover and measured what came out. It was exactly 8 qts. I put it back together and poured in the 8 qts. Don't start it yet. Then I diconnected the top line and hooked up my 3/8 clear hose and brass fitting. I had a pre-measured for 8 qts container. Started the car and pumped out 8 more qts, hooked the top line back up and poured in the remaining 8 qts. Toward the end, fluid was coming out nice and red. Definitly a complete fluid change.

[MAC]

Well, if you want to replace all the fluid via top line into bucket method you'll need 4 gal's.

The capacity of the 4T80E is:

Dry: 15 qts

Overhaul 12.6 qts

Pan & side cover 8 qts

I know it's not dry, but replacing "all" the fluid requires 4 gallons. How I did it is I dropped the pan and drained the side cover and measured what came out. It was exactly 8 qts. I put it back together and poured in the 8 qts. Don't start it yet. Then I diconnected the top line and hooked up my 3/8 clear hose and brass fitting. I had a pre-measured for 8 qts container. Started the car and pumped out 8 more qts, hooked the top line back up and poured in the remaining 8 qts. Toward the end, fluid was coming out nice and red. Definitly a complete fluid change.

Does your Eldorado have more than 100K miles. I'm somewhat concerned about a fluid change since my trans has 214K and I certainly don't want to stir things up too much and end up causing the trans to fail. Just curious if your trans is fine, particularly if you have over 100K.

[clarkz71]

No Mac, mine just turned 60K. I did the fluid change at 55K. I agree with 214K I would just do a drain & fill. (8 qts) That's if this is the first time it's been done. If it's had the fluid changed at least every 100K you should be OK with a complete fluid change. (15 qts)

[mmarinov]

Does your Eldorado have more than 100K miles. I'm somewhat concerned about a fluid change since my trans has 214K and I certainly don't want to stir things up too much and end up causing the trans to fail. Just curious if your trans is fine, particularly if you have over 100K.

My trans is in great shape @ 105K. I was considering changing the ATF but am kind of backing away from that position based on Poobah and Ranger's posts. I'm all for preventative maintenance but I don't want to wind up with a leak, either. My fluid (while not bright new red) is in no way burnt, brown, or otherwise foul looking.

Mark

[clarkz71]

I have changed several when they hit 100K and never had a problem. Personally, I would not let it go beyond 100K for fear of a leak.

Ranger didn't say don't change it 100K, he changed "several" at 100K,

and never had a problem! Nows the time to do your's.