Manual Transmission Flush: Options

[HeX]

I'l be performing a tranny flush soon on my '97 Civic HX (D16Y5) and would like to clarify exactly what is the best method. I've researched this a bit but much of the information is a few years old and most of the threads bounce around different options. Here's what I know for sure.

My understanding is the tranny flush process is easy enough.
1. Raise up the car on jack stands (the obvious, but some newbie is bound to ask)
2. Remove the filler hole bolt (to allow for breathing) then the drain bolt.
3. Re-install the drain bolt with a new crush washer.
4. Using a tube (is it 3/8?) and funnel, fill the tranny back up using 2 quarts of Genuine Honda manual transmission fluid until it begins to drip out the filler hole, then re-install the filler hole bolt with a new crush washer.

Here is where some confusion occurs with other options to consider adding to the basic flush listed above.

1. I read that some additional SyncroMesh fluid (GM or Pennzoil) also helps but I'm not certain as to how exactly, if at all. It apparently helps better lubricate the synchros for smoother shifts, such as to reverse. Some even say that using engine oil will suffice, but all I've ever heard from reputable mechanics is that it may help for short term but should not be used long term, at least not on Hondas.
2. What exactly is a "Flush and Fill"? Some claim to drain the old fluid then refill with either cheap fluid, synchromesh, or standard fluid, drive it up to operating temperature, then re-drain that and refill with Honda fluid.

Lastly, how often should a flush be performed? I believe the standard interval is about 50k miles or sooner if the engine is ran aggressively. I personally believe in doing it every 30k-40k miles max, or at roughly 3/4 of the recommended interval. As inexpensive as a flush is to perform compared to replacing the transmission, I just makes more sense to do it sooner and be on the extremely safe side with any tranny.

In short, this is what I'd like to confirm and perhaps make a concise How-To about:
1. Should only Genuine Honda Manual Fluid be used? (2 quarts, at least for D-series)
2a. Is blending it with SynchroMesh a legitimately beneficial option, and why?
2b. What should the ratio be when using the two?
3. Is a flush & fill process really beneficial or just overkill? Why?
4. What size hose fits into the filler hole?
5. What size sockets are needed for both bolts? 14mm?
6. what size crush washer is needed?
7. Is it best to perform the flush with a warm tranny in order to better get all the fluid out?

I'd like all responses geared towards LONG TERM transmission health in mind with explanations provided.

 

[XpL0d3r]

I did a transmission flush earlier this year with my RSX. I had a second gear grind. I switched to Amsoil and the grind is gone. When I had my Civic, I used Synchomesh and never had any problems. Didn't blend with Honda fluid, just used straight up Synchomesh. I also recommend a magnetic drain bolt.

So to answer some of your questions:

1. No, genuine Honda or Synchomesh. Not sure others in a D series motor.
2. Good question lol. Never heard about or looked into blending them. I'd be interested to know this one myself.
3. It's beneficial. I don't think you need to get back up to operating temp. With my RSX, I drained the fluid, installed magnetic drain bolt, filled with cheap fluid, started the car and cycled through the gears a few times. Then drained, saw a bunch of metal particles on the drain bolt, cleaned them up, reinstalled and filled with Amsoil. Without the flush, those metal particles would still be floating around in there.
7. I've heard both... warmer = thinner so you'd get more fluid out. But colder = fluid has settled and sits at the bottom. I did my RSX when it was warm.

It is also important to make sure the car is level when doing the flush.

 

[dancam]

I would just use honda fluid, amsoil or redline. That seems to be what people like. I wouldnt mix fluids. Oils have a lot of different additives which react with eachother, sometimes badly if its the wrong kinds or ratios. I you want syncromesh use just GM stuff.
I drain when warm. Then the oil is more fluid, and the particles are in suspension and come out. When its cold most particles sink to the bottom yes, but they tend to stay on the bottom in the pan and not come out.
I wouldnt flush with a different brand. The reason your flushing is because not everything comes out the first time, but if you put cheap fluid in for a flush and then good stuff you still have a lot of the cheap stuff left in there. Same bad idea as mixing oils. Different brands have different additives and react with eachother. If you want to flush then use the same oil you will be putting in at the end. Personally i would do more frequent changes than flushes. If you look at honda trans fluid oil analysis on www.bobistheoilguy.com youll probly come to the same conclusion as me that 30k miles is about as long as that oil should go. It shears really bad and quickly.
So, honda fluid is not that expensive compared to anything else good and is whats meant for the car. Thats what i would use. With proper drain intervals and normal driving it should easily outlast te engine. If your racing or whatever maybe a boutique oil like amsoil or redline is better, but look at used oil analysis and what people who have done it say about it because i dont know if it would actually help.
Flushing does help, but it would be more benificial for the life of the car to do that with your engine oil than transmission oil. Just change it regularly. If someone grinds your gears for you maybe flush it but use the same kind of fluid! It would cost the same and take the same ammount of work to cut your drain interval in half as to flush every time. The way the oil shears its probly better anyway


Sent from my iPhone using Tapatalk

 

[mc360]

transzex on d-series.org is the tranny guru, he says to run regular old 5w-30 in honda transmissions. think about it b series calls for regular oil if i remember correctly, d series calls for honda mtf but transzex says that the new formula for the new honda mtf is terrible. really just use what ever you want, i bought a bottle of syncromesh like a year ago and then just ended up buying a case of honda mtf. and i believe your supposed to change the tranny fluid every other oil change so every 6,xxx miles but im sure most people neglect this, i know i have only ever changed my tranny oil twice

 

[HeX]

The more I keep reading elsewhere, based off your comments, the more I'm lead to the conclusion that Honda changed their manual tranny fluid formulation a few years ago (sometime around the late 2000s) and its nowhere near as good as it use to be. This is likely from the change in engine design science, similar to why older engines need "higher mileage" oil.

I don't see much said about Amsoil while Redline seems to be better recommended for those in colder climates. The biggest consensus continues to be that using pure GM Synchromesh manual fluid is the best option with no issues mentioned anywhere I can find. GM relabeled their products under AC Delco, including the most preferred version being the AC Delco Synchromesh Friction Modified manual tranny fluid. Again, all I read is improvements from using the Friction Modified fluid more so over the standard Synchromesh. FYI, Pennzoil Synchromesh is NOT the same as AC Delco but they are similarly formulated.

Unless someone provides better info, I'll be going the route of the Synchromesh Friction Modified fluid with the use of a magnetic drain plug. I'm thinking it'd be smart to do a flush run with the magnetic plug to catch any lose metal fragments. Can anyone else answer these remaining questions? Please do continue to share your educated thoughts and information.

4. What size hose fits into the filler hole?
5. What size sockets are needed for both bolts? 14mm?
6. What size crush washer is needed?

 

[mc360]

I believe the drain and fill ports are both 17mm bolts, I know the fill port is. Pop your hood and the big bolt next to your passenger axle is the fill port

 

[Turbo_Freak]

To remove the drain plug on the tranny you use a 3/8 ratchet. No socket needed. You can service the tranny by removing the VSS on top of the tranny. Just make sure you remove the fill port on the side.

 

[Joe Mason]

I bought 1/2 inch tubing then used a straight razor to taper it down to fit perfectly into the fill hole. Also bought the crush washer from the dealership. The most difficult part of the process was breaking the drain bolt loose. I don't think it had ever been removed.

 

[HeX]

I made my decision and ordered online the AC Delco Synchromesh Friction Modifier for the tranny. The local dealership said each quart cost about $29, which is ridiculous. So I found 2 quarts online for $29 & change, shipped.

To remove the drain plug on the tranny you use a 3/8 ratchet. No socket needed. You can service the tranny by removing the VSS on top of the tranny. Just make sure you remove the fill port on the side.

I noticed the drain plug this past Sunday, but thanks for the info. I hadn't thought about using the VSS hole to refill it. Its a good idea I'll likely try.

I believe the drain and fill ports are both 17mm bolts, I know the fill port is

Thanks. I did spot them this past Sunday while rotating the wheels. Thanks for confirming the 17mm size.

I bought 1/2 inch tubing then used a straight razor to taper it down to fit perfectly into the fill hole. Also bought the crush washer from the dealership. The most difficult part of the process was breaking the drain bolt loose. I don't think it had ever been removed.

My tranny had been flushed about 4 years ago when I had the clutch replaced so the bolt shouldn't be seized. My buddy who owns a shop did it so I'm not worried about anything being previously over-tightened either. The tube slicing is also a good idea but I may first try Turbo_Freak's suggestion of using the Speed Sensor hole instead since its easier to acess from above and allows me to view when the fill-hole begins to spill over. I found a good deal on eBay for Skunk2 magnetic drain plugs for the tranny and oil, which include the crush washers, so that's one less thing to worry about.

I read so many opinions about the magnetic drain plugs and found most of them to be gross overstatements against their benefits. The logical conclusion is that they definitely cant hurt by preventing less internal shavings from moving about thus helping reduce added wear, regardless of the magnitude.

 

[XpL0d3r]

The logical conclusion is that they definitely cant hurt by preventing less internal shavings from moving about thus helping reduce added wear, regardless of the magnitude.

Exactly. I threw in a magnetic drain bolt, flushed, and saw a whole bunch of metal shavings on the bolt. I'm going to guess they were not helping my second gear grind. After the flush, the grind was gone.

 

[HeX]

I'm considering instead of doing a quick flush before adding the Synchromesh Friction Modifier to use my telescopic magnet stick and put it through the fill hole then the drain hole to grab as much debris as possible, being careful of course. Any thoughts on that idea?

 

[dancam]

You could. I dont think you would get much though. They tend to stick to things and rub off whatever they catch.
But You could do that, then blow it out with compressed air, then run the much cheaper honda mtf for 10k or so, drain that and put in the GM stuff. It would be like a flush without wasting as much money


Sent from my iPhone using Tapatalk

 

[HeX]

You could. I dont think you would get much though. They tend to stick to things and rub off whatever they catch.
But You could do that, then blow it out with compressed air...

I may not get much but every little bit helps to some degree, which is the point. Doing so would cost me nothing but a few extra minutes, so its "worth" it. I want to baby this tranny not just because its my daily driver and I currently intend to drive it into the ground, but one dream goal is to swap my engine & tranny into a 5th gen. hatch and drive that until its death or mine.

... then run the much cheaper honda mtf for 10k or so, drain that and put in the GM stuff. It would be like a flush without wasting as much money

Now that Dancam brought it up, I've heard several conflicting suggestions as to how long I should run a "flush" fill before putting in the good stuff in the tranny. I've read suggestions ranging from just driving up to operating temperature, to driving a few hundred or thousand miles as a flush. It seems to me like a short drive makes more sense. Otherwise, driving longer is the equivalent to just completing a fluid change and re-doing it sooner than needed. I wouldn't mind putting in the synchromesh now and re-doing it in a few months with more synchromesh, but in my case that sounds like overkill being that the tranny was flushed about 40k miles ago when the clutch was replaced.

 

[dancam]

I may not get much but every little bit helps to some degree, which is the point. Doing so would cost me nothing but a few extra minutes, so its "worth" it. I want to baby this tranny not just because its my daily driver and I currently intend to drive it into the ground, but one dream goal is to swap my engine & tranny into a 5th gen. hatch and drive that until its death or mine.


Now that Dancam brought it up, I've heard several conflicting suggestions as to how long I should run a "flush" fill before putting in the good stuff in the tranny. I've read suggestions ranging from just driving up to operating temperature, to driving a few hundred or thousand miles as a flush. It seems to me like a short drive makes more sense. Otherwise, driving longer is the equivalent to just completing a fluid change and re-doing it sooner than needed. I wouldn't mind putting in the synchromesh now and re-doing it in a few months with more synchromesh, but in my case that sounds like overkill being that the tranny was flushed about 40k miles ago when the clutch was replaced.

Yup, i would probly do it too, might try it next time i change mine depending on what you report back. I like people who drive cars till they die while taking care of them just keep in mind that most cars rarely or never have the mtf changed and the manuel trannys are almost never the cause of death of the car. When they do go its usually from abusive shifting/grinding or hopping the wheels while launching-none of which fluid will help.
My suggestion for the flush was with cost savings in mind-not whats actually best. What would be best for longevity would be a day or 2 of driving with the syncromesh then drain an fill with more syncromesh. However manuel transmissions dont seem to wear unless shifts get messy or that crunch going into reverse.
For example: i have a 1993 ford festiva with 430,000km on it. A few years ago it started leaking bad and i was always adding fluid. I got tired of using the speced mercon atf so i just used engine oil. Had to top it up once a month with about 1.0L (takes 2.5). That worked for probly a year till i forgot to fill it once and ran it dry. Seized up doin 100km/hr. I stopped fast :p hitting the clutch didnt help. I filled it back up with oil and kept driving. I lost 5mpg and when i took corners hard you could hear tinkling... I started using atf a while back again, i ran it dry again and just managed to stop before it seized up earlier this year. I go through about 1.5L/month now and never change the fluid. It runs quite low sometimes though. I dont notice the difference until its about 1.25 litres low on a 2.5l system. I have added 1.5L before without having had it seize up. All my gears work just fine and it shifts good. No noticable difference except a drop in gas milage from 55mpg to 50. I ran it on 10w30 for probly 100,000km. Changed the fluid 3 times in over 200,000km because of cv shaft changes and to get rid of my tinkle
So manuel trannys are pretty bulletproof if you drive nice.


Sent from my iPhone using Tapatalk

 

[HeX]

Im definitely not one who believes in ragging a car to death. I just think its stupid to drive a car harder than its designed for. The day I want a car to rag on it'll be 'cuz I can afford something that can handle how hard I want to push it.

While I agree that manual Honda transmissions usually go bad from abusive use instead of natural wear from reasonable driving, I cant agree that fluid plays little to no part in it. Unless I know for a fact that the previous owner didnt abuse it, maybe I wouldnt worry. Not knowing what my tranny was subjected to for the 138,000 miles prior to my ownership, I choose to baby it from here on out to make it last smoothly, more so with it being an HX tranny thats not as available as others.

In regards to your example... umm, if you were regularly putting in fluid then you were basically constantly flushing it so your point actually coincides more with my reasoning. Besides, I'm more of a backyard mechanic and I will never claim to be an expert in automotives. When I learn something new, I employ it. Had I known about the synchromesh when my clutch needed replacing then I would've done it then. For now, I may just buy some pennzoil synchromesh from a local autoparts store and drive it a few days or for one long drive then flush it and put in the good stuff. I'll definitely update this thread down the line.

 

[HeX]

...manuel trannys... manuel transmissions ...

Unless you had a hispanic guy named Manuel shifting gears for you, I believe you meant "manuAl" transmissions.

 

[dancam]

Im definitely not one who believes in ragging a car to death. I just think its stupid to drive a car harder than its designed for. The day I want a car to rag on it'll be 'cuz I can afford something that can handle how hard I want to push it.

While I agree that manual Honda transmissions usually go bad from abusive use instead of natural wear from reasonable driving, I cant agree that fluid plays little to no part in it. Unless I know for a fact that the previous owner didnt abuse it, maybe I wouldnt worry. Not knowing what my tranny was subjected to for the 138,000 miles prior to my ownership, I choose to baby it from here on out to make it last smoothly, more so with it being an HX tranny thats not as available as others.

In regards to your example... umm, if you were regularly putting in fluid then you were basically constantly flushing it so your point actually coincides more with my reasoning. Besides, I'm more of a backyard mechanic and I will never claim to be an expert in automotives. When I learn something new, I employ it. Had I know about the synchromesh when my clutch needed replacing then I would've done it then. For now, I may just buy some pennzoil synchromesh from a local autoparts store and drive it a few days or for one long drive then flush it and put in the good stuff. I'll definitely update this thread down the line.

I wasn't saying the fluid plays no part, just that syncomesh, honda mtf, atf or motor oil wont protect any better or worse than each other when grinding a gear or hopping a wheel. There for sure is a difference the rest of the time. Just that a trans thats not abused at all might last 500,000miles on 10w30 and 3 million miles on syncromesh. If your car is gonna rust out before 500k then there is no point in fancy fluid. But if it sees abuse, history is unknown, your car will last a long time cos of no rust or you just like your car then more expensive stuff is worth it.
My example with the mazda trans wasn't about fluid so much, i do know it was changed (not flushed) regularly by what leaked. But, it ran very low on fluid, with the wrong fluid regularly and was seized twice. I used to race it all the time, went to the local track, taught 7 or 8 people how to drive a standard with it -so lotsa ground gears. Towed a lot with it. Its taken a ton of abuse. And its still fine.
However, when i drain the fluid it never smelled, even the first time back in 2007 when it probly still had the original trans fluid from 1993, lol. But when i did the trans fluid in my 7th gen civic with 200k km it stank so bad. I used to work as a mechanic and did all the oil changes in that smaller shop, had to check the trans and diff fluid on every vehicle that got an oil change. Changed a lot of them too and my civic trans fluid was up there with like the top 20 worst smelling oils. I work in a quite large shop now, finished changing the civic trans fluid at 8am, turned all the exhaust fans on and my boss came in at 10 and complained about how bad it smelled still. So these honda transmissions could be a lot harder on oil than my festiva trans.


Sent from my iPhone using Tapatalk

 

[mc360]

I would throw oil in for 500 miles then drain and refill, no need to waste money on the "good stuff" only to flush it out and waste it.

 

[HeX]

UPDATE:

I changed the tranny fluid today and I instantly felt smoother shifting upon driving. I performed the drain on 4 jackstands and lowered the front passenger one for better drainage. The filler bolt was in fact 17mm as @mc360 stated (Thanks). I also installed the Skunk2 magnetic drain bolt, which is 17mm as well. I poured in the new fluid through the speed sensor hole as @Turbo_Freak suggested (thanks), which was easy and convenient as it allowed me to view the filler hole while I poured from above. I did feed the telescopic magnet into the tranny & got a few metal shavings between that and running it through the drained fluid. Fortunately, there was very little found. The fluid looked very transparent and had no discernible smell.

With that said, I figure in a few hundred miles I'll just feed the telescopic magnet through the filler hole again and decide whether or not it needs another flush at that time. I'll chime in a few hundred miles from now with updates on how this AC Delco Synchromesh Friction Modifier continues to do.

 

[Shaaaft]

I have to do this soon... Really soon actually. Lots of helpful info in here.