Ford 6F35: What have we learned?

Mar 18, 2007
How far will the 6F35 go? Most folks threw in the towel early in the life of the vehicle, citing immediate complaints about shift quality, shift flares and shudder. Some of us saw units fail before 20,000 miles for largely unknown reasons. Even once Ford went ahead and rebuilt or replaced units, the same concerns were right back as soon as the adaptive shift strategy took hold. My newer Fusion continues on with its 6F35. Every day is a huge question mark to the integrity of the transmission. I've drained and refilled the transmission nearly 10 times (2-3 times at 3 different intervals) since I've owned the car and I'm nearly positive that fluid maintenance is the only thing keeping it in a plateaued state of functioning since I bought it two years ago at 36k miles. The inconsistent shift quality is the least of my concern most of the time, however a constant shuddering under load along with intermittent severe shift flares (generally only when transmission is cold) This is an expensive transmission. The cheapest I've seen a new 6F35 go for is around $4,000, before installation. I don't want to take the hit on getting rid of the car, especially since I love nearly everything about it (the transmission excluded, of course), however losing some money (negative equity; high mileage:model year) would be less of a hit than buying a new transmission at any point in the car's lifetime. I don't want a change from Mercon LV to be the nail in the coffin for this unit. I've just recently had the latest calibration update performed under Ford's CSP for the throttle body failures. This was primarily an engine calibration update, but I can tell they definitely tweaked a few things in the transmission file. While the newest calibration does seem to offer a slight bit more predictability to the function of the powertrain, it doesn't worry me any less about a premature failure of this transmission. My question is, being that the current software is probably the last update that Ford will release, the only updates come in the form of fluid technology, short of rebuilding the unit using all the latest Sonnax updates. I've seen it repeated over and over that REDLINE D6 with an added dose of LubeGard Red has the remarkable ability to lessen the disconcerting behavior of the 6F35, thereby possibly prolonging its life. I recently stumbled upon a BITOG thread started by a member regarding a collection of people submitting fluid samples to Blackstone in the effort to establish whether the transmission is wearing itself out, leaving the fluid contaminated with aluminum and clutch material or if the ill behavior doesn't seem to be affecting the unit, which would assume that Mercon LV really does just darken for no reason, which I really have a hard time getting on board with. The only part that makes me question all of this is the fact that the '13+ Fusion is still using the 6F35 with some excellent success, along with using Mercon LV. What changed? If I had Ford replace my aging 6F35 tomorrow with a new unit, would it function as well as a 2013+ Fusion's 6F35? TL;DR Do we have any other high mileage 6F35 owners out there that can definitively distinguish that a move away from plain Mercon LV over to Redline D6 with an additive (or similar) was a move for the better in reducing 6F35 operation concerns.
Wouldn't buy almost any car or truck now without a manual trans.The automatics are too complicated for their own good.And I laugh how they keep coming out with new fluids to deal with these troublesome transmissions as if its as simple as a new high falutin fluid that can keep flawed electronics from doing damage.ATF+4,Dex VI,Mercon LV and all these other updated fluids are nothing more than bandaids devised to counter poor engineering.If a 727 TorqueFlite could live behind a Hemi dragstripping in the 60s,there is no reason why todays advanced trannys/electronics and fluids can go 100K miles without failure.Should be closer to 200K now.
The issue with all of this "innovation" is that it's all in the name of fuel economy. Lower RPM shifts whenever possible to increase fuel economy, requiring "smart" software to predict the needs of the vehicle operator to allow for efficient usage of torque at a given speed. Too many variables for the software available in today's vehicles. All I know is...I'd rather have my old GM LN3 3.8 with a THM440T4 Hydramatic running the show in my car. That was a good example of a well engineered, long lasting powertrain. Why do they keep releasing new products without thoroughly R&Ding every part of the vehicle? I love my car in every other way...really.
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.
The ZF trannies seem to do well. The one in the company Navigator still acts like a lady, even after being subjected to dragging out loads 2-tons over towing capacity at full throttle through our dirt lot on rainy days, up launch ramps, and just towing it around in general. It too, however, does the stupid-shifting at times. It's like it doesn't want to downshift, no matter what.
I think they'll go for a reasonable amount of time, but shift quality and timing just won't be there strong suit. The reflash and D6 seem to be the biggest fix we've gotten yet.
So I'm definitely down with the D6....already ordered for my next drain and fill. .. My next question... how do we feel about Seafoam TransTune? I've used it with excellent success in nearly every car I've owned, however, none of those cars had a transmission similar in design to this (those were 4 speed hydramatics). My thought is, there has to be a substantial amount of varnish buildup in this trans from how hot I know that it's gotten over its life...but if you all think that D6 and lubegard will do it, then I won't complicate the mission. Thoughts?
There is no need for a solvent in your transmission. Besides D6, Amsoil ATL is another option. A Magnefine should be considered. If in a warmer climate, or stressed driving, consider a quart sized PH8A remotely mounted filter, with side effect as an external sump for better ATF temp control.
I just got the wife's flashed for the throttle body issue and saw a big improvement. I'm hoping they made it a little less 'adaptive' and it keeps performing like it does right now. In a couple of weeks it's getting the first of a series of drain and fills with MaxLife with a switch to D6 planned if needed. It's got 52k right now so I can't comment on what's going to happen with high mileage 6F35's. But I don't want to find out - I'm hoping to convince her to trade it in once it's paid off. Unless I see a lot of high mileage 6F35's rolling around and it turns out all this worry was for naught. The biggest complaint I have about it is that it seems to go into neutral when braking or coasting. Has anyone else noticed this? If I need to get on it fast after coasting or braking for a while (like trying to swing out of a slow moving lane into faster traffic) it won't go for a bit, then slams into gear from high RPM. I know the slam can't be good for the tranny, but it's also unsafe - I'm trying to merge with traffic, I expect the car to go, but it's just sitting there. It's pretty dangerous if you're used to a car that goes when you hit the gas.
I've never understood why these ford 6f35 transmissions seem to be far more problematic than the gm 6t70 I believe. I thought they ( gm and ford ) co-developed these transmissions. Our 2007 Saturn made it 136k not great but not bad either. The performance was solid as we'll. Did ford take a few shortcuts ? I'd like to know? Thanks
Originally Posted By: Greasymechtech
There is no need for a solvent in your transmission. Besides D6, Amsoil ATL is another option. A Magnefine should be considered. If in a warmer climate, or stressed driving, consider a quart sized PH8A remotely mounted filter, with side effect as an external sump for better ATF temp control.
In this instance, I sort of agree. I'm not only apprehensive about adding a solvent like TransTune, but it doesn't seem like it would offer the same benefits that it did in my older HydraMatic(s). I'm a huge fan of AMSOIL, I've been a preferred member for several consecutive years, only just last month letting my membership lapse for the first time. I'm a little bit hesitant to use ATL over D6 in this particular transmission, ONLY because of all the success shared by others using D6 for this application. In addition, the Redline is just ever so slightly cheaper without having to renew my AMSOIL membership, directly from my vendor of choice for anything and everything, Amazon. I feel like I'm not going to trust in this D6 to last a whole lot longer than the Mercon LV, so I'm going to plan on changing it in 30k miles, as I usually do. If it doesn't improve shift quality substantially, I may keep the LubeGard Red, but might add it to a change of Mercon LV for comparison purposes. Mercon LV is $4.50 cheaper per it's a lot better suiter for the frequent changes that I like. I definitely need to do my research on the Magnefine filters. I don't feel that I'd benefit as much as if I'd installed one <50k miles, but if I've learned anything about transmission it's definitely fluid
So, I'm on the first few days of driving since the change. I did the transmission fluid with D6 and lubegard red, brakes with ct3 pads and raybestos at rotors, and an oil change with Toyota 0W20 and a motorcraft filter (the first non amsoil in 30,000 miles). Initial impressions are good. Either the fluid itself or the lubegard has significantly reduced the acceleration and low rpm cruising shudder. In addition, the shifts are smoother (read slipping by design), and over all, operation has improved. For reference I used 3.75 QTS of D6 and 1 full bottle of lubegard red (10 oz) for final fill. Prior to that, I did two full 4 qt drain and fills with D6 before disconnecting the battery and doing the final fill. I'm definitely thinking about adding D6 to my next T-IV change in the '07. I'll update as time progresses. Thanks for your support on this topic guys.
Thanks for the update. RedLine D4 would be a good replacement for T-IV. Lubegard can be added to all but I dont see the need for it with aftermarket full synthetic ATF. But, if it is working for you, keep adding it. Everyone can benefit from ATF filtration. Wear is continuous in the transmission. Worn valve bodies/components have grown significantly in the need past decade. I'd wager that suspended abrasive wear in the fluid is a good honing media...think grand canyon affect.
Reports are that people have completely solved their shift problems with this transmission by running Premium gasoline. That simple. The poor shifting appears to be a computer/software issue, and the higher octane seems to solve the problem.
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Originally Posted By: Elroy the Unique
Reports are that people have completely solved their shift problems with this transmission by running Premium gasoline. That simple. The poor shifting appears to be a computer/software issue, and the higher octane seems to solve the problem.
This is true in some cases. Most folks don't realize today that the transmission computer and engine computers are interconnected and rely on each others data.
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.