Poobah Posted August 21, 2006 Report Share Posted August 21, 2006 This morning, I took my recently purchased Deville in for service and a good looking over. My mechanic tells me the transmission fluid smells bad and should be flushed and changed. I remember reading on this forum that it is not a good idea to flush the transmission, just drain and refill. He says the advantage to flushing it is that only about a third of the fluid comes out when you just drain it. He also said that the only drawback to flushing that he knows of is if the mechanic doesn't know what he's doing, he can contaminate my transmission with somebody else's dirty fluid. He assures me he knows how to do it right so that doesn't happen. What do you guys think? I can certainly see the advantage in getting all the old fluid out (especially if it smells bad). If the mechanic is able to prevent contamination, is it a good idea to flush it? Thanks in advance Happiness is owning a Cadillac with no codes. Link to comment Share on other sites More sharing options...
KHE Posted August 21, 2006 Report Share Posted August 21, 2006 The transmission fluid smells bad - does it smell like burned popcorn or just transmission fluid? There is no in-between - you'll know if it is burned. Transmission flushes are a huge money maker for mechanics. The risks are as you noted in your post. Also, even if the flush is performed properly, the magnet and pan must be cleaned. The drain and refill capacity of the 4T-80E is 11 quarts. The overhaul capacity is 12.6 quarts - for 1.6 quarts, I would not risk using a flush machine. You can always run the car for a few thousand miles and then drain and refill again. That would be almost a 100% fluid exchange. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
epricedright Posted August 21, 2006 Report Share Posted August 21, 2006 I called my local Caddy dealer and they told me the same thing. They said there was no way contamination could happen. Atlthough he sounded convincing, after reading here, I decided dropping the pan would be the safest route to go. He was able to change the filter and clean the bottom of the pan as well. Now that I think about it, maybe there was no filter....not sure. Maybe just the screen and magnet. Link to comment Share on other sites More sharing options...
adallak Posted August 21, 2006 Report Share Posted August 21, 2006 If you want to refresh the fluid completely, disconnect th ecooling lin eby the radiator end tank and run engine for a few seconds in P. You'll get ALL old fluid out and no damage will be done to the tranny. I did just that a month ago. Is the ATF dark? It changes the smell and gets discolored after years of service, but as KHE mentioned if it is burnt you cannot miss it. Your mechanic understands he will not damage anything (if he flushes properly), but the thing is that you just may not need to refresh ATF, or you can do it yourself at no cost. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
blunted Posted August 21, 2006 Report Share Posted August 21, 2006 DO NOT FLUSH, there have been way too many horror stories for anyone to ever convince me otherwise. Also, dropping the pan lets you clean the magnet and any gunk (which there very well might be) off the filter which could restrict flow. If you really wanna get serious with it, take a little extra effort and run it for a couple days and then drain/fill again, this way you know for a fact theres mostly clean fluid in there... great for the obsessive complusive caddy owner like myself. Link to comment Share on other sites More sharing options...
Ranger Posted August 21, 2006 Report Share Posted August 21, 2006 Here is what the Guru 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." Link to comment Share on other sites More sharing options...
JimD Posted August 21, 2006 Report Share Posted August 21, 2006 This morning, I took my recently purchased Deville in for service and a good looking over. My mechanic tells me the transmission fluid smells bad and should be flushed and changed. I remember reading on this forum that it is not a good idea to flush the transmission, just drain and refill.... Thanks in advance Is this something you would do yourself? Or would have have someone else do the work? Jim Drive your car. Use your cell phone. CHOOSE ONE ! Link to comment Share on other sites More sharing options...
zonie77 Posted August 21, 2006 Report Share Posted August 21, 2006 I don't have the link anymore but one of the flush companies did not recommend flushing a trans if it had 100K miles on it. That tells us something. Link to comment Share on other sites More sharing options...
Poobah Posted August 21, 2006 Author Report Share Posted August 21, 2006 Thanks to all of you for your quick and thoughtfull responses, particularly to Ranger for posting the Guru's comments. (The Guru has helped me several times in the past and his advice has always been spot-on.) My mechanic said the transmission fluid definitely smells burned. Out of curiosity, what would cause this and is there a way to keep it from happening in the future? I thought flushing was done in addition to draining. I wasn't aware of the fact that a flush was done without taking off the transmission pan. Yeah, I know the kind of debris that settles into the pan and I wouldn't want it stirred up and cycled back through my transmission. I will have my transmission drained, have the pan cleaned, the filter and magnet cleaned and/or replaced, then just re-fill it. (Funny thing: I am an Architect and I am in the middle of a major remodeling of the home of a guy who's business is selling transmission flushing equipment and supplies.) I will have the work done rather than doing it myself. It's worth the cost to me not to have to deal with the potential mess, the disposal of the old fluid, the oily dirt falling in my face and eyes while I do the work, plus I have a serious phobia about the car falling on me. I just won't do it myself. Happiness is owning a Cadillac with no codes. Link to comment Share on other sites More sharing options...
epricedright Posted August 21, 2006 Report Share Posted August 21, 2006 plus I have a serious phobia about the car falling on me. Even with 2 jack stands and a hydraulic jack protecting me, I can't help having that same fear...too many movies I guess. I keep my stays under the car at a minimum. Link to comment Share on other sites More sharing options...
BodybyFisher Posted August 22, 2006 Report Share Posted August 22, 2006 If you do have it drained and refilled don't forget that there is a side pan drain, this was posted above.. 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 One of our members (blunted) had his tranny fluid drained and they forgot to drain the side pan.... remind them to drain it, Mike PS, i have not been to the scrap yard regarding your trunk nuts... Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
blunted Posted August 22, 2006 Report Share Posted August 22, 2006 One of our members (blunted) had his tranny fluid drained and they forgot to drain the side pan.... remind them to drain it, Mike Good point! Link to comment Share on other sites More sharing options...
jhall Posted August 22, 2006 Report Share Posted August 22, 2006 Poobah, Pull the pan and forget the flush "magic". You need to see the condition of the tranny internals via the deposits in the pan / around the catch magnet. BTW - Don't think for a minute that the flush will remove all wear particles and leave the tranny "sparkiling clean". A standard draining will do about the same and will also provide some idea of the wear rate (fine pwder versus metal chips). Keep us posted! Link to comment Share on other sites More sharing options...
GreenMachine Posted August 22, 2006 Report Share Posted August 22, 2006 I'm going to do this when I change my oil. Since the car will hit that 100,000 mile mark possibly by the end of the yar or early next year, may as well get a head start and change it before old man winter gets here. A few questions while we're on the subject: What transmission/transaxle fluids do you recommend? What do I need to do to reset the Transaxle Fluid indicator? From what I understand the differantial and Tranmission on front wheel drive cars are one in the same and combine to make the "transaxle" so I shouldn't need to change some differential. The Green's Machines 1998 Deville - high mileage, keeps on going, custom cat-back exhaust 2003 Seville - stock low mileage goodness! 2004 Grand Prix GTP CompG - Smaller supercharger pulley, Ported Exhaust Manifolds, Dyno tune, etc 1998 Firebird Formula - 408 LQ9 Stroker motor swap and all sorts of go fast stuff Link to comment Share on other sites More sharing options...
KHE Posted August 22, 2006 Report Share Posted August 22, 2006 I'm going to do this when I change my oil. Since the car will hit that 100,000 mile mark possibly by the end of the yar or early next year, may as well get a head start and change it before old man winter gets here. A few questions while we're on the subject: What transmission/transaxle fluids do you recommend? What do I need to do to reset the Transaxle Fluid indicator? From what I understand the differantial and Tranmission on front wheel drive cars are one in the same and combine to make the "transaxle" so I shouldn't need to change some differential. I have 8 gallons of SuperTech Dexron 3 Transmission fluid on my garage shelf in preparation for the fluid change on both of my Sevilles. Any trans. fluid that meets the requirements of Dexron 3 should be fine. There is no differential fluid as the diff. is internal to the trans. I think the trans fluid life is reset by simultaneously pressing and holding the OFF and REAR DEFROST buttons until the message is displayed on the DIC. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
joeb Posted August 22, 2006 Report Share Posted August 22, 2006 I always wondered why some FWD cars have a diff with 80-90W like my dodge and GM cars can get away with using tranny fluid for the diff? I drop the pan on my STS and have refilled several times with syn tranny fluid. makes me feel better. the dodge came with ATF3 but the latest advice is to use ATF4 which is supposedly syn stuff. still shifts fine after 175K miles. I can pump out 1 gal thru the dipstick tube which is nice. than i pour in a gal of fresh stuff. too bad the caddy fill tube is restricted so i can't get a tube down to suck out fluid. Link to comment Share on other sites More sharing options...
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