Transmission Flush -Good Idea or BS

I have a friend who swears getting his transmission (automatic) flushed every 50k keeps it running great. I will have to say he has 200K on a Chevy Tahoe, and my Suburban needed a ****** rebuild after 70k. I broke the sun gear -not sure how a flush would fix that.

I have asked a few transmission shops about this, and they didn't seem to think it was necessary.

I just got a 60 Impala with a Powerglide, and I thought it may be a good idea to get it flushed as it has been sitting for a year.

Anyone have any thoughts on this, or know a good transmission shop in Austin?

 

As long as the fluid is clear, clean and smells like oil, you are ok. If it is turning dark, feels gritty or stinks, it time.

 

i have 400k on a 7004r, never flushed, rarely serviced, generally abused

 

I have my grandfathers 1979 Ford F250 with a c-6. I have records dating back to new for a trans flush just about every year. It has about 150,000 on it and has been used to tow a fifth wheel almost all of those miles. The trans has never been out of the truck and seems really strong. I don't know if it helped it live longer, but time will tell.

 

in my experience as a former dealer tech, fleet mechanic (public works/public safety) and a shop owner, vehicles which have the transmission serviced routinely will always have an extended service life compared to those that don't. there is a reason you change your engine oil and filter right? a clogged filter or fluid that has lost its ability to perform its intended function will lead to premature transmission failure.

granted there are the mechanical breakages in things like sun gears that are a matter of bad design or poor manufacturing, but that aside, its a maintenance item like anything else. also there are also anomalies which are a matter of odds where you'll see a trans go bad after 60k for no apparent reason. but thats just the odds.

NOW... these BG machines that hook up to your ****** cooler lines and 'flush' or 'exchange' the fluid without dropping the pan and removing the filter make about as much sense as changing your engine oil and never changing the filter. you can actually wind up with a clogged filter.

also... if a transmission has a ton of miles on it and is already in a state of decline, a transmission fluid change can actually make things worse. fresh fluid has a detergent effect which can wash away carbon deposits on clutches and bands which effectively increases the space between the friction surfaces, creating the potential for slippage.

aside from regular fluid changes, the most important thing is keeping trans temperature down. excessive temperature is what KILLS transmissions. install a good cooler!

okay.. so then what?
on newer vehicles driven here in LA, i like to see the first fluid change done between 36-45k with additional services around every 15-30k depending on the transmission and fluid type. those intervals will change depending on the type of driving, but on most of the vehicles we see thats about normal. even newer cars are getting some REALLY good synthetic fluids that will go alot longer... like 100k or until it blows up type thing...

on older cars like ours, watch the fluid. when it stops looking like it did when it came out of the bottle, change it. when it starts turning from red to brown, gets cloudy or starts to smell toasty, change it. its an inexpensive maintenance item that can save you a ton of bucks and inconvenience.

 

I agree with alteredpilot, especially about the "flush". Before I retired I oversaw the maintence of several commercial vehicles and on a couple of occasions when we allowed a trans flush the proceedure blew the filter off. We found this out later when the transmission failed and the filter was laying in the pan. Never did that flush thing again.

 

Heat is the big killer of automatics. Never own a truck without an external cooler. If it does not have one, install one. Cheap-cheap insurance.

 

Yep

 

Just do a fluid change and clean or change the filter. Flush is generally bad. Some shops will charge you for a flush and never hook up their machine.

 

I dump the pan and change the fluid on any automatic I've got every 25-30,000 miles. If the filter looks like it needs changing at that time, I change it. As far as flushing goes, if something bad is stuck to the wall inside my transmission, I'd just as soon leave it stuck there, rather than stirring it up.

 

A flush with one of those machines is fine, but it's only worth the $$$ if the filter is being changed at the same time. The machine gets the fluid out of the converter where a regular pan drop can't. Basically it's just an easy commissioned sale for a dealership service writer to swindle a ***** new car owner out of their money without actually knowing any factual information on the service itself.

I've had GM/Ford Transmissions with over 300k that were never flushed and still operated like new. All they ever had was a filter change and a drain & fill, and of course an aftermarket trans cooler.

Got a C6 now and when the rear seal started leaking I drained the fluid & dropped the pan, installed a shift kit, replaced the filter, and added new trans fluid...trans has almost 200k of mostly towing miles. A $30 fluid cooler is probably the only reason that C6 hasn't taken a dirt nap since the fluid has never gotten hot enough to lose it's ability to lubricate.

 

The advantage to the flush is you replace ALL the fluid. By dropping the pan and changing the filter you leave some of the old dirty fluid in the trans. I like to replace the filter AND flush the trans. I have shop trucks (40L60E) with over 300K miles on them and no trans issues.

 

It looks like the answer is yes with a new transmission (with a reputable shop and a filter change).

I think I will follow alteredpilot's advice and leave the dirt where it is. I am going to be babying this car for a while anyway. I'll change it the old fashioned way -with a filter change and then keep an eye on it.

Thanks folks.

 

I bought a Ford pick up new. Had the trans flushed twice during the 1/4 million miles I ran it. All others I talked to with the same truck and set up went through 2 or more transmissions in fewer miles. Seemed like cheap insurance. The first flush found the filter had dropped off and was laying in the bottom of the pan. May have been there from the factory.

I also have a stock 55 Olds that I suggested having the trans gone through while putting in a new engine I got a good deal on. Original engine was just dirty from neglect when I got it. Trans fluid still looked good and everything was working good. Was advised just to drop the pan, replace the filter and bring fluid back up. All is still good.

Different strokes for different folks. Same seems to go for transmissions.

 

Any comments from the informed about the use of organic vs. synthetic trans fluid. I previously had an engine with a high thermal load (intercooled centrifugal blower) saved from certain death because I was running Mobil 1. If I had been running organic oil it would have been toast. The synthetic was pitch black after the near meltdown and the head gaskets were toast, but the engine survived. Can the same be said of running synthetic trans fluid? In the event of a higher than normal thermal load it is more likely to survive?

 

My dad didn't like the pressurized flush machines because the trans often leaked after the flush.

He would flush the ****** at home. He would unhook the cooler lines, put a hoseon the inlet in a 5 gal. bucket full of new fluid, then put a hose on the outlet into an empty 5 gal. bucket. Let idle, and wait for the clean fluid to come out in the bucket.

A flushed ****** without high pressure.

I found this to be true also about leaking. I had a 700r4 flushed at Chevrolet, and afterwards the tailshaft seal leaked.

 

Beat me to it.

Anyone with some sort of mechanical ability can flush the dirty fluid out of the torque converter during a transmission fluid change. Easy and cheap, it just takes couple more quarts of fluid to make sure the converter no longer has any dirty fluid left inside.

How to do it on a GM car with a crossflow radiator, others will differ:

Remove the pan to drain out all the fluid in the pan and ******. Clean the pan and reinstall it with a new filter and gasket, use no sealer on the gasket. Don't overtighten the pan bolts! Fill the trans with about 5 to 6 quarts of fluid.

Disconnect the upper trans fluid line on the radiator. This is the fluid return to the trans from the converter (unless they were switched at one time), trace it back to the trans and make sure it is the upper line of the two going into the trans.

Get a length of the same size line (5/16" or 3/8", whichever applies) from your local parts store that has the same flare and nut on it as the trans line, the longer the better. An old 'junk' trans cooling line will work too of course. Connect it to the upper fitting on the radiator and bend it by hand carefully so you can put the other end into a container or a bucket, I use an empty 1 gallon water jug.

Start the engine and let the 1 gallon jug fill about halfway up with fluid, use a helper to hold the jug if you need to. Stop the engine and add 2 quarts to the trans. Start engine and fill jug halfway again, repeat these steps until you have flushed about 6 quarts out of the cooling line.

The converter holds about 5 quarts, by flushing 6 quarts through it you will make sure it is full of clean fluid. This will also flush the cooler in your radiator at the same time. Reconnect the trans line and run the engine, top off with fluid. Keep the length of 5/16" or 3/8" line you bought for the next time you do a trans service. Do a final check of the fluid level with the trans good and hot after a drive.

 

I like the home flush method! May have to do that on my truck too!

 

I was always wondering since it is heat that kills your automatic transmission how come so few people have a trans temp gauge in thier car?

 

The 70s era cars had drain plugs on the torque convertor, do the newer ones still have them ?

 

cause idiot lights make it easy

 

My last job was servicing trans flush machines in new car dealerships, and other auto flush machines (brake, fuel, PS, Diff...yeah they make one for everything nowadays) I never believed in any of these machines or services. Sure flushing out your old fluids is good, and recommended for longer life, but you don't need these machines to do what you can do with a little inginuity.

These machines are just a fancy way to sell a "maintenance service" to an uneducated customer. They'll charge a hundred dollars or more to pump $15 worth of new trans fluid through your trans in about 10 minutes labor time. Most of the techs doing the work are lube techs without much experience working on cars. Most real techs who do these flushes only like them for the incentives they get for selling the flush services and don't actually think they do much good. I had to deal with the technicians on a daily basis, and 90% of them hated the machines, and hated doing the services. They were only happy when I gave them promotional **** like hats and mugs and incentive pay. It's all snake oil to me.

 

I've seen dozens of GM torque converters from the '60s & '70s and never saw a single drain plug on any of them.

I did buy one aftermarket high-stall conveter that had one and several more that didn't. I don't think that a drain plug on a torque converter is a common feature, at least not on GM cars of that time frame.

 

I bought my 59 Ranchero in 1996, looked at the fluid and it was nice and clean. I haven't touched it since. I will have to soon because the cork gasket is starting to seep fluid. I guess the fluid outlasted the gasket. I did install a cooler since I occasionally tow a car trailer. Never had any problems.

 

i look at them more as a fluid exhange than a flush. we sell them as flushes at work and thats how they are marketed to the customer. i will say when done correctly it is more effective at changing out all the fluid when compared to dropping the pan and refilling with 5 qts when most transmissions hold 8qts or more. i use the flush machine on my daily driver every 50k miles and i do recommend to get fluid changed using a flush machine. i dont believe in the chemicals that are sold with the flush and only use the cleaner if the trans is really bad. i have fixed a few minor trans shifting problems by changing the fuid. but if its worn or broke, the best fluid in the world isnt gonna fix it. the pirce of a flush at a repair shop includes the chemicals, fluid and labor, so its gonna cost way more than 5 qts and a filter kit.

 

I'm pretty sure it was just 70's to early 80's Fords that had drain plugs

 

Trans temp idiot lights??? Late model stuff you get a check engine light but...

 

I like the trans flushes. I prefer the flush with a filter change at the same time.

And I know for a fact that the BG machines work off of a bladder type system. Your trans pump provides the pressure to push the old fliud onto the top of the bladder that in turn pushes the new fluid on the botom of the bladder into you trans. No possible way to over pressurize using a BG machine.

Sun gear is usually broken by shifting from reverse to a forward gear without coming to a complete stop in between. Or vise-versa.

 

Another thing to consider, is the type of filter you have. Most modern trans use a dacron cloth filter, this type must be changed, as they ac***ulate fine sediment and get restricted. The screen type, as used in many older trans can usually be washed out with solvent. As stated above, the most effective way to service your trans, is drop the pan, change or clean the filter, remove the return line from the cooler, fill the pan with clean fluid, start the engine in neutral (especially with mopar) and purge the converter of fluid. I still maintain it is utter BS that changing your fluid can damage an older transmission. It is not going to "heal" anything, but it's definitely not going to harm it either. Included is a return line chart for various trans.

 

some newer fords have plugs in the converters too, 4r70w's like in pickups and suv's have a little rubber plug in the bottom of the bellhousing you can pop out to get to it.