Ford 6F35: What have we learned?

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Jan 6, 2005
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California
Originally Posted By: W_John_C
How exactly would raising octane levels fix my transmission concerns? There are many misconceptions about premium fuel. I am genuinely interested in hearing this theory if it's based anywhere in reality. I am aware that this PCM is capable of handing multiple fuel tables, obviously because its a flex fuel power train, but premium fuel by itself isn't high enough octane to trigger that fuel table to advance timings and cause any notable drivability improvement.
Using premium fuel works for whatever reason: http://www.fordfusionforum.com/topic/10692-switching-6f35-for-f21-aisin/
 

W_John_C

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Mar 18, 2007
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I wish I could make some more logical sense of this, but I must say, that only 50 miles into my first tank of premium, the harshness of response and shudder has even further diminished. I wouldn't call it a complete fix, but you can definitely tell that this engine is at its far limits for running regular fuel. It makes me wonder if a premium tune (steeda, etc) in concert with premium fuel would clean it up even more? Jury is still out, and it may be a placebo effect of paying an additional $0.30/gal but I will stick with it for a few tanks (being that it can't fully adapt to a new fuel table instantly) and see how it goes, both for performance and maybe even fuel economy?
 
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I can say on my Taurus, with the 6f55 (big brother to the 6f35), premium does get rid of some of the weirdness of shifts and such. Especially in the summer time. However, I just go cheap and put in regular. I also found mid grade gets rid of 90% of the weirdness in the summertime so I sometimes run that.
 
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Trans can adapt to fluid condition. Trans can adapt to drivers driving style. Trans can't adapt to knock sensor. It seems that it can't adapt to variable engine output at any given rpm and throttle position. Knock sensor causing ecu to aggressively pull timing whenever is too confusing for the trans. Pretty sad that it was missed in R&D.
 

W_John_C

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It's funny to me that I've never hooked up a scantool to watch live data on this vehicle, since I always have on nearly every vehicle I've owned previous. I might just get myself another live data handheld to take a look at KR/Advance with premium vs regular. I'd like to go high dollar to see the more advanced data from the transmission and find exactly where the miscommunication lies between the powerplant and the transaxle, but that's a whole new level of toy budget. Another update for premium fuel: Power increase across the band seems a bit more consistent. I found myself in some spirited driving yesterday being quite pleasantly surprised about the flat-out response. It could have been the cooler ambient temperatures, but it felt smoother as well as more powerful. Not bad in my book.
 
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Originally Posted By: Red91
I hope the new Chrysler 8 and 9 speed Torque Flights don't disappoint. It would be great if it ends up being a long lasting transmission. I've read good things about them, but time will tell.
I hope so too! Though, with all of the shifting that's going on in these new tranny's from any MFG., there has got to be a high failure rate...IMHO!
 
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Jun 4, 2014
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Dallas, Tx
I'm not fond of the latest trend of permanent filters on transmissions. I was very surprised after crawling under my '12 Fusion to find that there is no transmission pan, and you have to split the case to get at the filter. Isn't this a recipe for failure on older transmissions? At 100K, I took my '05 Sport Trac to Kwik Kar and had the pan dropped. That filter was beyond trashed. (I found out at this point that Ford had only been replacing the fluid every 30K and not touching the filter). So either the permanent filters are letting the finer stuff go by, or they're stuffed full of clutch material. How can this be good for a transmission? Or...do manufactuers really care about what's good, as long as it makes it past the warranty mileage?
 
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Wow, and I thought dipstick-less transmissions were bad. Although, is this filter just a mesh meant to catch the big chunks? Not a filter meant to catch small stuff, just big chunks? Supposedly the "filter" on my Tundra is a strainer, or so it says in the various parts supplies (and the dealer too, who didn't seem keen on selling me one).
 
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Just another example of disposble engineering and a lack of respect for the buyer. It is getting harder, but I buy automatic vehicles only with a transmission dip stick and replaceable filter.
 
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I've got a 2012 Fusion 2.5L with the 6F35 Tranny. I'm doing ok with it, I did 4 drain & refills via dipstick tube over 3 months, at the 3rd & 4th d&f I began adding LG Platnum. 1oz per quart. I haven't noticed a difference in shifting, but I'm sure adding LG-Plat is better than bare naked Mercon LV? My big issue with this tranny is it's inability to hunt quickly for a gear. If I"m crawling through traffic at a slow pace, and I see an opening to move lanes, flooring the gas will not yield a quick acceleration. Literally a 2 second delay before the engine revs, then the tranny wakes up and tries to find a gear to get moving in. It's kinda scary at times to do this. a steady acceleration however from moving slow for a bit will yield good results however. I think the car computer is in slow mode, then when you floor it, the computer goes.. WHAT HAPPENED!! and plays catchup. It's my only gripe with the Fusion. I don't want to bring it back to the dealer, as I'll have to pay for the software upgrade, as well as have them try to find a way to charge me for stuff I don't need done. I politely told them where to go for the 60k service. They don't call me anymore. every 7-8 days was getting annoying.
 
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I'm not sure that's the transmission's fault as much as it is the engine's. The 2.5 I test drove was a little sluggish and noisy. My 3.0 Fusion would bang off a downshift with lightening speed and chirp the tires under 35mph. Its tendency to hold rpms too long on slow acceleration was my gripe.... and some rough shifting when cold. Some mornings that thing would SLAM into reverse when backing out of the garage, even when idling at 850 rpms. A fluid change did little to help.
 
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@FocusTi Keep an eye on your throttle body.. the morning reverse slam could be from the TPS sensor not giving correct info to the car computer. There's a recall on the TB's for the Fusion's, Escape's and Edge's. But yeah, my 2.5 is noisy, it sounds like it's 3 qts low on oil, but it's fine. it doesn't use any oil between OCI's, which for me has been 10k with MC 5w20 semi-syn. For me it's been about gas mileage, hence why I went with the 4cyl. I have no regrets, I love my Fusion!
 
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Originally Posted By: michaelluscher
I think they'll go for a reasonable amount of time, but shift quality and timing just won't be there strong suit.
I agree. I would say that this applies to a lot of automatic transmissions in a lot of newer cars from all manufacturers.
 
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Jan 1, 2013
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South FL, USA
I've had one transmission replaced under warranty within the first month of purchase when new. It's been back on and off about 4 times for reprogramming. The last time I was told a part was changed and they changed the fluid. This was around 40k miles. I did a fluid drop and used the castrol lv fluid. It did shift more predictable. Then I read on here that motorcraft has a higher boiling point and castrol was dangerously lower. Now I'm at 53k miles and hearing a slight whine with the motorcraft. I'm leaning towards valvoline max life, but wondering how can it support LV, VI and all the other specs in between. Does that mean we can us dex VI and be safe too?
 

W_John_C

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So, I'm back. My trials came to an end on Oct 23 when the car was totaled out. I was rear ended hard by someone who wasn't at all paying attention. It's been a busy month since then. I think this is the first free moment I've had! Haha. I do want to say that I am almost certain that using premium fuel was helping the engine run with much greater advance and keeping it from stumbling most of the time, which took away a lot of what I thought the transmission was responsible for. In addition, I am reporting that LG Red with the D6 really did help the trans perform better in many conditions over straight Merc LV. I do recommend this combination very highly, and I think it's one of the best solutions out there for keeping your Fusion (or similarly powered car) driving as you expect! With all of that said...especially since I was just figuring out its idiosyncrasies, I really do miss that car very much.
 
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Jun 29, 2011
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Crawfordville FL
I have a 2010 Fusion with the 6F35. It was rebuilt around 63K miles because of slamming into reverse and funny shifting when cold. Dealer updated the valve body and reprogrammed the PCM. Since then it has been smooth shifting and well mannered under moderate/heavy acceleration. I wish they'd adjusted the first gear ratio to be a little bit taller as when accelerating from a stop, if you're kinda putt putting about it the 1-2 change will give you a pretty good bump as the RPMs drop... it "holds" between the gears until RPM matches. With heavier acceleration this isn't a problem as the revs change faster in the high RPM ranges. I would like to drive a Fusion with the 2.0L Ecoboost and the 6F35 to see if this improves with the smaller engine, which I assume changes revs faster due to less internal momentum. I now have 120K on the transmission and it's fine. It does whine, but it's not overly loud or annoying. I only hear it with window down around 40 mph in a pull uphill. After the rebuild and reprogramming I have been very happy with the car. To the poster that complained about throttle delay... Most of the time when I hit this issue it is because the transmission is still in 2nd as I'm rolling up to a stop, but hasn't yet downshifted to 1st when I get back on the throttle. The "hesitation" is intentional to allow the tranny to get into gear. That's my theory anyway. I adjusted my driving style and have almost eliminated these "hesitations". Pretty much, stop at the corner before pulling out. This puts the tranny back in first and that big low gear will bark the tires when you punch it. To the guy that thinks Mercon LV was developed as a band-aid... nope. They moved to Mercon Low Viscosity to reduce internal pumping losses. It's all about the MPGs I haven't done anything to the transmission Maintenance-wise since it was rebuilt. I figure I'll have the tranny flushed around 150K which is when the owners manual says it's needed. I've used MC 5w-20 with MC filters until the 100k warranty was up, now I'm on Mobil 1 0w-20 extended life with Mobil 1 filter
 
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