Tranny flushing...yes or no? - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 02-27-2005, 12:44 AM   #11
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a double flush is what he did because my fluid was black..they use a chemical that allows you to do a transfusion without stirring up the crap in the tranny...some BG company... and the motor vac is a chemical also..similar to the GM stuff you mentioned..
pulse the injectors with it and it cleans the motor...
james
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Old 02-27-2005, 02:01 PM   #12
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OK, I'm glad this worked out for you. The ONLY other thing that I would have done would have been to drop the pan after the flush and clean the pan and maget and also to replace the xmission oil filter. I know this sound really stupid after you just replaced all the oil in the system. But the fact remains you still will probably have a dirty pan and a magnet that is full of junk from years of neglect. The xmision filter also was probably never changed in years also.
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Old 02-27-2005, 06:31 PM   #13
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NO

"The following is from a GM powertrain engineer. It is on a Cadillac site but the fundimentals are the same.

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'* 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'* 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."
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Old 02-27-2005, 08:56 PM   #14
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Quote:
Originally Posted by Ranger
Read the factory service manuals and point out the place where a transmission "flush" is recommended.
The topic of Transmission Flushes will be debated ad nuauseam. No Where in the FSM does it tell anyone to do a xmission flush. It also says that we do not have to change our xmission oil for 100,000 miles, our engine oil for 7,500 miles, and our coolant for 150,000 miles. We have some members that have NEVER changed the xmission oil for over 200,000 miles and their cars performs just fine. We have others that change their xmission oil "by the book" only to see their xmissions die shortly there after. And still others that change their engine oil every 2000 miles and xmission oil every 6 months thinking this will prevent any catastrophic damage to their drivetrains. As you know, there are no guarantees in life. But we do what we think is best for us.
The "cooler line" trick is not for the faint of heart and I would not do it. If this were my car, I would drop and clean the pan and magnet, replace the filter and oil and around 6 months later, do it all again. And then make it an annual service event.
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Old 03-09-2005, 07:27 PM   #15
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Every 100,000 miles the tranny is supposed to be flushed. However you had better make sure the fluid is out of the torque converter or you're asking for problems. It takes a special machine to do this. If you want it done right, go to your local Pontiac dealer and have it done. They will do a good job and you will not have any transmission problems if you don't have any now. It is relatively inexpensive $140.00 and they also put in the conditioner. My "93" SSE has 213,000 miles and the transmission shifts fine and doesn't leak. I have this vehicle serviced on time all the time and it runs strong and perfect. I just had the 200,000 mile service done on the tranny, and no problems. Good luck.
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Old 03-09-2005, 08:13 PM   #16
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I did a flush every year on mine (with the proper machine) for $80 (not a dealer service department), and it held up to MAJOR abuse for a long time. 110,000 miles under a modded SSEi.
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Old 03-09-2005, 09:28 PM   #17
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alright ill chime in on this post i think From what I've learned and seen there really shouldn't be a problem flushing a tranny... The thing that happens alot with a flush on a car that hasnt had for even 75000+ miles is that the original oil in the tranny was basically keeping the tranny running.. the trannys can be so wore out that they actually need those little pieces in there in order to even run.. so the second they get a flush there tranny is toast... preatty much comes down to how you treat your tranny basically.. debris fills up holes .. just drive the car like a normal person and it should be fine for years.. unless you can upgrade your tranny with stronger parts... then you can drive like an A$$ all you want
later
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Old 03-19-2005, 08:15 PM   #18
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I know of two types of trans flushes. Most splice into cooler line. Other type (harder to find) removes pan and hooks up to suction part of trans. Second style replaces or cleans filter and cleans pan. Had both ways done with no probs. Corrected shift probs on my truck.
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Old 03-19-2005, 08:50 PM   #19
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for the kind of tranny flush where they splice into the cooler lines, exactly where in the lines on a Bonneville would they do the splice. I had my transmission flushed at the Pontiac dealer a little while ago, and then recently I noticed that one of the rubber hoses at the upper passenger side of the radiator, which go to the aux. trans oil cooler, was leaking and so I had both pieces of rubber hose replaced and 4 new clamps. Is it possible that this is where they spliced in to do the flush, and might have damaged the hose or not connected it back up properly, in the process?
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Old 03-19-2005, 09:02 PM   #20
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Here'* my experience with flushes. I've had two. The first: Tranny started losing TCC lockup when it got warm. Got it flushed, the place had me sign a waiver first that they weren't responsible for soon to come failures because my tranny showed damage. It completely let go 2.5 months later. It would only go into gear when really cold.

Second: one year after rebuild, it was sticking in second and felt a little wierd when it finally shifted. Been fine since the flush. I have recently developed a shudder I thought was a miss, but I've tried most remedies for that and nada. I am planning on a fluid and filter change very soon.
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