- Introduction
- Improve Fluid Quality
- Increase Fluid Amount
- Change Fluid Type
- LSD Conversion
- Final Drive Gear Ratio Change
- Machine 3-5-R Drum
- Install Sonnax Zip Kit
- Upgrade Torque Convertor
- Billet Flex Plate
- Transmission Friction Clutches
- Treat The Transmission…
- Transmission Upgrade Companies?
- Other Things…
- Resources
Introduction
The 6F55 that is found in many late-model Ford and Lincoln vehicles has traditionally been the bottleneck to potentially greater power output on any of the transverse 3.5L EcoBoost platforms. There has never been much aftermarket support for it (if any at all). But how much power can it be made handle? I think the engine has proven it can make power, that hasn’t been in doubt…it’s getting that power through the transmission that is the real question. The goal for this post is to put everything I can think of that can possibly be done for the 6F55, regardless of how effective, into one location. I’ll try to keep it updated as developments and discoveries are made. Feel free to reach out for any commentary or other ideas.
1) Improve Fluid Quality
Oil is one of those things that are always argued about…which brand is better than any other. I can’t say that I have definitive controlled testing on what is better than anything else, however, the majority of people have run either of the two below and have had success with them. I’m sure there are other brands that folks will swear by, but these seem to be the most popular.
Ford Motorcraft makes a pretty decent oil and is the go-to for many people. There hasn’t been any negative aspects to it, so you’d likely be perfectly fine running it.
As for the folks that like to splurge a bit…Amsoil is a great brand. They have a good reputation and their Signature Series ATF has been run successfully in many of the top EcoBoost platform performers.
2) Increase Fluid Amount
One common theme voiced by many tuners and performance enthusiasts is the increase of transmission fluid amount, AKA…overfilling it. It isn’t much, but the rule of thumb has been to overfill by a pint. What this attempts to address is the fluid moving away from critical components within the valve body during very hard acceleration events. A pint isn’t alarming enough to set off any nannies and it’s just a bit more fluid in the right places at the right time.
Check out the discussion about it here:
https://shoforum.com/threads/over-fill-trans-oil.138608/
3) Change Fluid Type
There’s been some rumblings recently about trying some of the Motor Company’s ULV transmission fluid. The theory here is to keep the oil a bit more viscous, allowing it to flow more freely, especially at colder temps. The effect is potentially quicker and more firm shifting, from what I can understand. It’s all still experimental and the jury is still out. I’ll wait until this idea is fleshed out a bit more to see if there is any viability at all to it.
Check out the discussion about the Mercon ULV Blend here:
https://shoforum.com/threads/im-switching-to-mercon-ulv-blend.143693/
4) LSD Conversion
Here’s a pretty good one. Recently discovered by Andrew Bullock, the current record holder for the SHO 1/4-mile, that an already available part for the GM 6T70 will fit the 6F55.
https://www.tractionconcepts.com/Chevy-Impala-LTZ-6T70-HD-Upgrade-LSD-Kit-p/tcxchg5323.htm
What are we trying to accomplish here? Well, keeping both wheels on either side moving translates to better handling and quicker acceleration. This platform has an open differential, in both front and rear. Generally speaking, what that means is that the tire that begins slipping actually receives the most power. This isn’t what we want. I personally sufferer from wheel slip on hard launches. It’s typically the front passenger wheel that falls prey to this phenomenon. Getting both tires to drive the vehicle forward could significantly lower 60′ times and really make this platform a contender.
Obviously, a full-on, dedicated LSD from any of the big brand names would be the most ideal scenario. There’s no argument there. But with the lack of any aftermarket support in this area, the Traction Concepts LSD conversion blocks are the next best thing. This type of device has had an interesting history as a quick Google search will show, but the application of the technology and implementation is sound. It remains to be seen how well these will actually perform, but I am optimistic there will be some gains in this area. Adding to this, Traction Concepts customer service is outstanding and they’ve now dedicated a product line for this transmission as well as a matching counterpart for the Rear/RDU.
Front/Transmission:
https://www.tractionconcepts.com/Ford-Taurus-Sho-AWD-Front-6F55-6-Spd-Auto-LSD-Kit-p/tcxflmg5332.htm
Rear/RDU:
https://www.tractionconcepts.com/Ford-Taurus-Sho-Ecoboost-AWD-Rear-LSD-Kit-p/tcxflm2804.htm
Check out the discussion about it here:
https://shoforum.com/threads/traction-concepts-lsd-conversion-kit.144108/
And here’s a great video, done by Andrew, on it:
There was some discussion at one point about getting WaveTrac to jump onboard developing a proper LSD, but initial buy-in was so high, it seems this idea died on the vine.
5) Final Drive Gear Ratio Change
This isn’t talked about much, but I’ve had some discussions with a few of the top EcoBoost performers and there is a theory going around that this platform may benefit from going to a shorter final drive ration (counter-intuitive). This theory may hold some water as it relates strictly to running the quarter-mile and not for daily driving.
Depending on which transverse 3.5L EcoBoost you have, there are a few final drive ratios to speak about. The early SHOs as well as the non-PP iterations all ran with a 2.77 final drive. The later models and PP SHOs (as well as the Explorer Sport and Ford Flex Limited) all had a final drive of 3.16.
If you notice, all the top SHO performers are non-PP. The trap speeds are highest among that final drive. If you’ve run the quarter-mile in this platform, you’ll notice that you shift into 5th gear shortly before reaching the finish line. You will never shift into 6th gear while running the quarter-mile and you wouldn’t want to anyway as that is an overdrive gear. 1:1 is 5th gear in all iterations. The current theory is that this puts the car too low in the power band to continue any real acceleration, lowering trap speeds. However, those with the 2.77 final drive push the finish line still in 4th gear.
I will speculate that, for this platform and strictly for the quart-mile, going to a final drive of 2.77 may actually help. This doesn’t help daily driving, however.
So what would need to be changed? Well, that remains to be seen since no one has done this. But as the final drive ratio is done within the transmission and not anywhere else, it may be relatively straight forward. It may just be the ring gear for the front differential and the pinion gear.
If experimenting the other direction, there are a few more versions of the 6F55. One with a 3.39 final drive, one with a 3.43 final drive, and another one other with a 3.65 final drive.
This is all just bench-top racing and is simply a discussion. Here are some online discussions about gear ratio changes:
https://shoforum.com/threads/3-16-drive-ratio-change.114282/
https://shoforum.com/threads/3-39-gear-ratio-change.132811/
https://shoforum.com/threads/any-significance-to-the-final-gear-ratio-choices-available.132949/
https://www.taurusclub.com/threads/gear-ratio.310913/
6) Machine 3-5-R Drum
This is one of those preventative-type modifications to be done if you find yourself digging into the internals of the transmissions or if you find it is what failed. What is interesting to note here is that this failure has been random, from the evidence that I’ve seen. It hasn’t been related to high power output or any potential extreme driving scenarios. It seems to fail at all points of the power spectrum.
To summarize, a large snap ring that holds parts of the 3-5-R drum together doesn’t appear large enough and under certain conditions (unknown exactly which conditions) will break. The answer has been to machine a larger groove and replace with a more robust snap ring. I haven’t been able to get details on what exact snap ring size or where to source it, but as I find that information out, I will update this post.
Here are some links that discuss the issue a bit more:
https://shoforum.com/threads/arggggg-dredded-p0756.134215/
https://shoforum.com/threads/found-a-tranny-upgrade.139943/#post-1517564
https://shoforum.com/threads/drivetrain-strength.141583/page-11#post-1541149
https://shoforum.com/threads/transmission-rebuild-upgrade.141649/page-2#post-1546023
https://shoforum.com/threads/jordans-rebuild-plan-of-action.141297/page-19#post-1547439
https://www.ecoboostperformanceforum.com/index.php/topic,6655.msg103207.html#msg103207
7) Install Sonnax Zip Kit
Sonnax offers a kit to upgrade certain components within the valve body. There hasn’t been much discussion on this but the kit is available and Sonnax is a respectable transmission brand. I believe I’ve even heard that this is installed by the dealer if there has been a failure of the valve body, but don’t quote me on that.
https://www.sonnax.com/parts/3743-zip-kit
8) Upgrade Torque Convertor
There is a bit of history here. I don’t personally consider the torque convertor as actually part of the transmission-proper. However, it’s close enough to the system to be worth discussing here. Currently, GearHead is the main supplier of improved torque convertors for the platform. You won’t find it on their website, but you can contact them and they will give you the information you need.
Early on, Circle D made an upgraded TC that had a higher stall speed. It was discovered that increasing the stall speed on this platform wasn’t actually ideal and performance ended up suffering. That, combined with the fiasco that is called Nick Olsen (long time EcoBoost enthusiasts will know the name) is what got them out of the game, IIRC.
As such, GearHead is the only real option out there currently. So what is done to it? Well, they have a custom billet stator to help redirect fluid for maximum possible efficiency while unlocked, brazed fins for durability, and more lockup clutch area with a higher energy material. It’s been used effectively in many of the top performers.
Important note. GearHead only offers this in the 3-bolt pattern. If you have an older 4-bolt model (2010-2012 SHO, I believe), you will need to upgrade to the 3-bolt flex plate. Regardless of what you send GearHead as a core, you will only get the 3-bolt from them. It’s easy enough to convert, just get a flex plate from a 2013+.
Here’s some conversation on it:
https://shoforum.com/threads/torque-converter-increased-stall.142614/
https://www.ecoboostperformanceforum.com/index.php?topic=10714.0
9) Billet Flex Plate
It remains to be seen if this is a worthwhile modification, but it’s cool enough to be mentioned. Spearheaded by Mike Kraus of the SHO Forum, it’s a beautiful piece. Reactor Products is a small company with awesome customer service. The stock flex plate is pretty light (~5lbs) and this piece is ~5lbs as well, so weight reduction is negligible. The piece is far more robust, however, so that is a good selling point. Has the platform hit the power levels where we are worried about the flex plate being an issue? Not really…but why not, right?
Here is some discussion on it:
https://shoforum.com/threads/bpd1151s-2010-sho-rebuild-thread.139715/page-18#post-1536349
10) Transmission Friction Clutches
Raybestos
First let’s talk about the Raybestos friction clutches. They are currently dead in the water and it doesn’t look like they will ever be produced. But not all hope is lost. This is a product that many of us are chomping at the bit for but can’t seem to get our hands on. It’s a product that was born out of social media pressure, crowd-sourcing and a grassroots attempt at getting something to market for this platform. Follow the thread below for some history on it:
https://shoforum.com/threads/help-me-try-to-get-a-performance-part-made-for-our-platform.142595/
Here’s some basic info on the different friction materials that Raybestos generally offers:
And a short video explaining this:
This would help the platform transmit the power a lot better through the drivetrain. Unfortunately, release of the product seems stalled by a number of things. Part misunderstanding and part supply chain issues, this product may never see the light of day. Fingers crossed…
I won’t go into all of it here, but here’s the current situation on these:
https://shoforum.com/threads/raybestos-update-and-call-to-action-lets-do-this-again.144298/
Make sure to reach out to the current designated distributors of the product to try and keep interest up (maybe even place an order, though you won’t see the product for some time).
https://transmissioncenter.net/?s=r…utes=1&tags=1&sku=1&orderby=date-DESC&ixwps=1
https://suncoastdiesel.com/p-35846-home-gas.html
Here’s a cool promotional video made for the product early-on. Many of the cars in it, you may recognize.
More discussion on it here:
Helix Autosport
I mentioned earlier that not all hope is lost. Enter the company Helix Autopsorts. A company out of the UK that was discovered by Andrew Bullock during his insanse SHO build. It is smaller company that builds quality transmission parts. Andrew has taken the lead on this and with any luck, they could potentially develop a friction material along with maybe a billet clutch basket. Fingers crossed, but I’m feeling positive about this one…
Check out the discussion on them here:
https://shoforum.com/threads/helix-autosport-uk-stepping-up-to-manufacture-upgraded-clutches.145062/
11) Treat The Transmission…
Yes, treat the transmission to dinner every once in a while. It will treat you nice in return.
Wait? What?
LOL, no, this section covers some aspects of treating the components with various services that are said to improve the quality or durability.
I’m personally a big fan of WPC treating. What is it you ask? Well, better to check out the videos below as they do a much better job of explaining it.
If you do a YouTube search on WPC, you’ll find quite a few real world testimonials. I won’t add them all here, but it’s pretty convincing, IMHO. I’ve used it for various other components and will use it when I get the transmission worked on.
What parts to do? Well, I’d say moving components that see wear and that mesh with other parts in an oil-filled environment, such as:
- Differential Gearset
- Planetary Gearset
Another type of treatment would be to cryogenically (cryo) treat, or “cold forge”, some of the same parts. WPC also offers this as a service. The jury is out on this, but it’s been done for many years and is nothing new, just not done often.
Here’s an older video covering the topic.
You decide. Figured I’d cover it as I’m throwing everything on the table here.
12) Transmission Upgrade Companies?
I wanted to touch on some of the current transmission offerings that are currently available. Many of these rear their head form time to time on various social media platforms.
SP Precision
https://spprecision.com/products/6f50-6f55-transmission-sale.html
This transmission finds it’s way into the limelight every so often and is billed as coming “loaded with upgrades”. This can’t be farther from the truth. I’ve personally called them to ask about this transmission and even they have said that it’s essentially just an OEM-build. There’s nothing “upgraded” about it. Frankly, it likely uses non-OEM parts and, unless I know where these parts are coming from, as far as I’m concerned, is inferior. Even the description is incorrect, stating the transmission was built from 2006 to 2012. This transmission went on to power models all the way up to 2019. This tells me they haven’t updated their description for the product in years. And $2000 for an OEM-refresh (not including installation labor) is a bit on the high side…
My rating? 1 out of 5 stars…don’t mess with it.
Level10
https://www.levelten.com/default.asp
Personally, this shop ranks up the with Livernois as a clown show. I know many of you may have used them and may even swear by them. I used to think they were the “cat’s meow” as well, but once I heard some of the shenanigans they’ve pulled, I will never give them a dime of my money.
Their “bulletproof” transmission is multiple thousands of dollars and yet, no one knows what actually makes it “bulletproof”. Likely nothing and this is also just an OEM-refresh that has been WAY overpriced and sold with deceptive marketing tactics.
Unless they can produce a build sheet of what exactly they’ve done to make this thing “bulletproof”, they have no leg to stand on, IMO.
My rating? 1 out of 5 stars. If you know you’re getting an OEM-refresh, you’ll be fine, but still…that is just WAY too much money for that level of build.
So at the moment….there really is no TRUE upgraded/modified transmission available. Mostly because there are just no parts available off-the-shelf. Anything done to the 6F55 will have to be one-off and custom.
13) Other Things…
Launch Control. It’s actually more of a 2-step. This isn’t transmission-related per-se` but using some form of launch control in conjunction with some of the above-mentioned modifications can reap some significant benefits. I won’t go into it too much as it’s covered pretty well in the following write-up:
Resources
Here are some pretty cool resources on the transmission. Most of it is good if you want to nerd out on specifics, but it’s still very good stuff. I’ll add to this as I discover more. If you have any cool resources, reach out to me and I’d love to add it here.
Sonnax 6F50 & 6F55 Valve Body Parts Breakdown
https://d2q1ebiag300ih.cloudfront.net/uploads/tech_resource/645/Ford_6F50-VBL.pdf?v=1600202306375
Sonnax 6F50 & 6F55 Critical Wear Areas & Vacuum Test Locations
https://d2q1ebiag300ih.cloudfront.net/uploads/tech_resource/663/6F50_VTG.pdf?v=1588869233162
Sonnax 6F50 & 6F55 Identification Guide
https://www.sonnax.com/tech_resources/663-ford-6f50-6f55-identification-guide
GM 6-Speed 6T80 MHM Hydra-Matic Automatic Transmission Specifications
https://gmauthority.com/blog/gm/gm-transmissions/mhm/
Sonnax 6F50 & 6F55 Concerns & Repair Techniques