Transmission Flush

[One Acre Farm]

Just purchased an 03 silverado that I plan on doing some towing with. It has 100k miles and I want to change the transmission fluid. I have been told by one mechanic that a flush is the best option, I have been told by another mechanic to drop the pan and change the filter, he claims a flush isn't the answer cause you want to leave some fluid in the system. He explained that the clutch additives were helpful. (or something to that effect) Any thoughts?

 

[moship]

Flush is the only way to get a larger % of the old fluid out, however the filter is not typically changed during the process. If planning on keeping for any length of time have the trans flushed and ask them to change out the filter also. Unlike years ago, most filters are screens and not fibrous material.

I am not aware of any reason why it is necessary to keep any fluid in the trans during a pan drop vs. flush. When rebuilding an auto trans the system is fairly dry except for possibly prefilling the torque converter.

Would you only want to change 1/2 the hydraulic fluid in your tractor and call it good?

It is common during the flush to add a cleaner first, drive for 10-15 minutes, flush and install and additive package. Some companies that sell the flushing equipment/fluid will warranty the trans depending on the mileage at time of flush.

Additives in automatic transmission can make a big difference and is how some of the OEM's alter their shift characteristics. It's crazy how they use chemistry to impact symptoms.

 

[timswi]

Have it flushed..I had an 04 that needed this every 40k or so and the performance difference is very noticable.

As was said, there's just a screen, so no filter to replace..Supposedly the flushing process takes care of cleaning it.

You really don't want to leave old fluid in there if it can be avoided.

Costs about $160 at the dealer.

 

[crashz]

I've never flushed them, however all my vehicles have the filter and pan fluid changed yearly and a pan fluid change at each oil change. Saves going to the dealer for a flush and I've never really liked the "bucket" method.

Without know the maintenance history, I recommend a flush as well.

 

[Diamondpilot]

Do the flush. I do it my self by dropping the pan, changing the filter, topping it off, removing the output hose off the tranny cooler and putting it in a bucket, starting it with a helper, pumping out 4 qts, fill, pump out 4 qts more, fill, pump out 4 qts more, fill, pump out 4 qts more, top off and drive.

Cost about $60 to do it yourself. If you are not comfortable doing this take it to the dealer. Either way, flush it. The second guy you talked to is dumb as a box of rocks. Flushing is always better.

Chris

 

[brokenot]

I don't think flushing is a bad thing, but why isn't it recommended in the maintenance schedules of most vehicles? In many cases, I think it's one of those service practices that's offered up by garages because the cash register likes it.

On another forum, I posted that I thought it was mainly a "gimmick-sell" because most maintenance schedules don't include it. They say to change the fluid at recommended intervals, but don't mention flushing at all. One member scanned and posted his entire maintenance manual to "prove" they did recommend it...but he didn't read it real close, because it simply said "change" as well. The only time "flushing" appeared, was in reference to the cooling system. If they recommend flushing anything, it's called out specifically.

I overhauled automatics for years, so I'm not unfamiliar with their inner workings. I just think that had the owners simply dropped the pan and changed the fluid as recommended, most of those transmissions would have never ended up on my bench. (Well that and sticking with recommended towing guidelines and such.)

A vehicle sitting still in park with a cooling line loose will get out more of the old fluid than just dropping the pan, but if you're just sitting there in park idling there's not a whole lot going on. Servos, pistons, clutch packs, valve body ports and pathways, etc. will be sitting there essentially doing nothing.....and as such won't benefit from the flushing. Show me a flushing apparatus that allows the trans to be shifted through the ranges under a light or no load simulating and easy cruise down the road to really flush things out...and that would be another story. That's not how it's done however, and if it were done that way the sign outside the garage wouldn't read "$99 Trans Flush Special".

For a DIY-er, I think sticking to recommended change intervals is more than adequate. Reading the actual owners manual and heeding payload and tow ratings is a good thing too.

 

[Hematite]

Brokenot, I agree completely. A fellow that I worked with had his auto trans damaged at a dealer because they set the pressure too high on the flushing machine. Blew out a spot on the casting. They "fixed" it with a wad of epoxy putty. LOL. Leaked after that.

Drop the pan, change the filter (extremely important), use a parts cleaning brush (new) and solvent and air to clean the debris from the pan and put the pan back and replace the oil. Never "wipe" the interior of any trans with any type of cloth. The tolerances on new transmissions are so close that the tiniest lint will cause a problem. Unless the fluid has been ruined (burned) by abuse, that is all that an auto trans needs to have done.

 

[brokenot]

Unless the fluid has been ruined (burned) by abuse, that is all that an auto trans needs to have done.

Funny you should mention that, because lots of the trans flush questions and answers I've stumbled across on the 'net have originated with a post from a vehicle owner that has burnt fluid and/or a transmission that's acting up. So it seems like a lot of the folks that are curious about it, haven't had their curiosity peaked because they're really all that maintenance-minded. It *sort of* appears to be considered in lots of situations as a "fix" for one thing or another.

I'm still unconvinced, because it's simply not recommended. I think instead of a flush at 100,000+ miles, the normal fluid changes should occur at the recommended 30 or 40K intervals. Doing it the other way kind of sounds to me like ignoring a bearing repack recommended service interval that's around every 40K or so....and then doing it really well at 100K by cleaning the parts in a jewelers ultrasonic cleaner instead of the old parts washer in the corner.



Once again though, I'm not "against" the so-called flushing, I just wonder why the OEMs didn't put a convenient downward-facing tee fitting in one, (or both), of the cooling lines. It could be easily hidden, (if they so desired), so Joe Homeowner couldn't easily access it, but it could be opened up on the hoist at the dealership to make flushing simple without having to muck about with line fittings.

But they don't, so....

 

[Hematite]

The homestyle "flushing" that Chris recommends, above, also can be a problem. Since you are working with a bucket, there is an excellent chance that dirt of some nature is going to be introduced into the transmission. Either from clothes, gust of wind, dust, etc. It doesn't take much to screw up a transmission.
I believe the transmission flushing machine came into use to wholesale remove fluid in a transmission that has been abused. Unfortunately, at that point, changing the fluid is probably a waste of time, the trans is toast. As long as the trans is maintained and not abused, I feel the filter replacement and pan cleaning is more than adequate to ensure reliability and longevity.

 

[Diamondpilot]

When I do a bucket flush the bucket is only used to catch the old fluid. I pour the new fluid in via the dipstick with a funnel from the qt containers it comes in.

Also, many modern trannys have no filters. Same thing with fuel systems. They are sealed units.

Chris

 

[wsp617]

Not long ago I was talking to a guy and it turned to a tranny flush debate. I told him that I had talked to guys that had trannies flushed and it performed so much better. He told me he and others ended up having to buy rebuilts after getting them flushed. He said by reversing the flow of the tranny fluid it lostened the particles. He said his tranny lasted 600 miles after the flush. He told about a relative of his that also had to replace the tranny, 900 miles after the tranny flush. The dealer won't warranty it because it was a high mileage tranny.

I've never had one done so I have no personal experience. Does anyone know, do they reverse flush the transmission when it's done? It would makes sense that they would because you would want to "flush" all the crap out if possible. What happens if you don't get all those loose particles out? Should you manually move there gear selector through all the gears when flushing?

I know we used to reverse flush the cooling system when we flushed them but that doesn't have all of the moving parts either. Thoughts?

 

[orezok]

In a former life, I used to own and operate a transmission shop. It was before the days of the flushing machines. I've done considerable research on the subject and other than the enhanced profit the business generates I don't see any advantage over just a change.

On my personal vehicles I change every 30,000, sometimes less if I doing some hard pulling of the RV through the Sierra's. On those that don't have it, I weld in a drain plug to the pan at the first change.

As far as filter changes go, I cannot remember ever seeing a filter that needed changing unless the trans was already toast. If there is enough soft part material or hard part material in the filter to warrant a change, the trans needs a rebuild.

Knock on wood, but I have never had to rebuild one of my own transmissions.

 

[Hematite]

When I do a bucket flush the bucket is only used to catch the old fluid. I pour the new fluid in via the dipstick with a funnel from the qt containers it comes in.

Also, many modern trannys have no filters. Same thing with fuel systems. They are sealed units.

Chris

That procedure, in itself, is risky. I would have to think that it is possible to temporarily run it dry or overfill. The way I've heard it done you use 2 pails, one to catch the old fluid and one pail with the new fluid in it. That way, the trans is simply pushing out the old and drawing in the new.

Yes, many car transmissions are sealed and with them a machine or bucket flush is the only option. As far as truck transmission, I don't know which if any are sealed or have no filter. Thank God, my F150 4R75E still has a serviceable large filter and removeable pan.

 

[Diamondpilot]

As stated above a filter is a false sense of security. With trannys being so sophisticated by the time you find something in the filter its too late.

As for my bucket flush technique. I simply pump out the same amount I put in. Start it, pump out 4 qts, replace 4. Not rocket science. You will see a difference in color as the new stuff starts pushing out the old.

Chris

 

[Hematite]

Well, I disagree about the importance of a filter. As precise as modern transmissions are built, something as small as a piece of lint can cause a serious problem. You may take a filter out and cut it open to check for debris caught but any large debris that you "see" is not what would have ruined the trans. It's the very small particles that aren't obvious but are caught in the filter. Ergo, the reason that you NEVER wipe the inside part of an auto trans with any kind of cloth. Anyway, I DO believe in the importance of a filter.

If you're careful, which I'm sure you are, with the method of adding as the trans pumps out, the way you describe, I would think that it would work well.

 

[tractorboy5500]

If just doing the flush, how do you clean the magnet without dropping the pan, I have done a few transmission oil and filter changes, and alot of the time the magnet looks like a grassburr with alot of metal dust and particles stuck to it. Not sure if all vehicles have magnets in the oil pans, some dont have drain plugs, but the ones that do have the drain plug are magnetic, and still when doing the flush the plug isnt pulled and cleaned.
And most filters have a gooseneck which plugs into the transmission and there is a seal for the gooseneck, after time the heat will make this seal hard and brittle, and start to suck air and after time will make the pump go out. I am a firm believer in changing the filter and seal if there is one, a flush is probally good after the first transmission oil change, thats when it is the worst, after that the magnet dont look near as bad, its part of the break in, i try to do my first transmission oil change a little early because of this.
When having a transmission oil and filter change, i ask to see the old filter and seal, that way i know it was done.
Not saying a flush is bad, I would highly change the filter the first time on a new vehicle when it is time to so, when the next time it is time, a flush would be good enough.
This is just me, not saying this should be put in stone.

 

[JakeBrake]

Here's my problem.

I have a 2001 Buick LeSabre with 185,000 miles. It has been a great car. I have noticed a significant fluid leak under the engine compartment. At first I thought it was engine oil. but I took samples on a white paper towel from the driveway and from the oil dipstick and from the transmission dipstick. To me all three look alike. I can't tell one from the other. I have done this when the car is hot and when the car is cold.

My last oil change was 3,000 miles ago. The oil looks good and very little has been used.
My last transmission service was 60,000 miles ago. Obviously, the transmission fluid should not look like engine oil, but the transmission shifts OK and there has been no significant fluid loss.

I have decided that I am going to do something about this next week. Now I have to decide whether I am going to take it to my regular general mechanic or to a transmission shop.

 

[orezok]

That procedure, in itself, is risky. I would have to think that it is possible to temporarily run it dry or overfill. The way I've heard it done you use 2 pails, one to catch the old fluid and one pail with the new fluid in it. That way, the trans is simply pushing out the old and drawing in the new.

The return line has no suction to pull oil in from a second bucket. The only suction is from the pan through the filter. The oil cooler line is strictly a pressure line that returns to the pan.

Running it dry is not really an issue. At idle there will be enough oil film on the rotating parts to prevent damage for a short period of time. Hyundai dealer service manual actually tells you to pump the oil out until it stops flowing and then shut off the engine and refill. I would guess that since they warranty the trans for 100,000 miles they probably know more about it than I do.

 

[Shenniu SN25]

05 silverado 4l65e just replaced tranny at 91000 miles! Did the tranny flush at 50000 used castrol trans fluid and replaced filter 40000 later no 3rd gear. I do a lot of hauling though camper,boat, tractor... Always used tow haul. Not a good tranny for towing.

 

[timswi]

05 silverado 4l65e just replaced tranny at 91000 miles! Did the tranny flush at 50000 used castrol trans fluid and replaced filter 40000 later no 3rd gear. I do a lot of hauling though camper,boat, tractor... Always used tow haul. Not a good tranny for towing.

Had mine flushed at the dealer every 30-35K...Never had a problem with my '04.

Either DIY or at the dealer, whatever...All of the old fluid need to go either way...old school dropping the pan and refilling doesn't work anymore. My owners manuals suggest that this be done.