3.31 to 3.73 Torsen Impressions for EB Mustang

[DANA44]

I have not flashed it yet, I asked LMS about it and they pointed me to a $235 ford oem programmer module for making calibrations, the dealer (which I called and they said they didn't know if they could do that) or the pro-cal / sct / cobb aka any tuner (their system is an PCM flasher / code reader only).

I'm still not 100% sure if it even needs done, the cruise control is dead nutz on. My GPS records the same speed I set my cruise to. The Speed is pretty darn close, it reads within 1-2 mph at most of the GPS and cruise (the fat needle isn't super precise for determining speed to that accuracy anyway unlike my certified speedo in the 9C1 police impala I had during college).

So I'm really starting to wonder if I even need to have any cal done. Perhaps the speedo reads via axel rotation (aka wheel sensors) rather than via trans gearing? If it reads via axel speed then no cal would be needed, if it reads via trans speed then a cal is in order but I"m starting to think it's unnecessary.

Is the flash needed with an automatic as the system as more data input with gearing where as the system has no gearing data with a manual?

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[5.0yote]

Is the flash needed with an automatic as the system as more data input with gearing where as the system has no gearing data with a manual?

No the speedometer gets its input now from the ABS speed sensor, not the transmission. They are unrelated. Do not quote me on this part, but unless the transmission is getting speed data from the same source then it should be auto adjusting on its on within reason, I would not imagine they would put that type of control in the hands of just an ABS module to help the AT regulate gears, shifts etc. I think its just the speedo and cruise.

This is just related to vehicle speed info for your dash.

I suspect it (the 6R80 AT) still has its own speed sensor.

 

[hungryhippos]

Not exactly. I ended up swapping the EB pinion flange to the GT diff, bought 3 pinion flange nuts (only $3 each from the dealer) just in case I needed to take it off or swap back to the stock diff. You can order the pinion flange for $75 but the dealer messed up the order and gave me the drive shaft coupler instead...so I had to re-use the stock pinion flange.

The EB and V6 manual pinion flange is the same as the GT automatic pinion flange interestingly enough. I'm not sure about the automatic EB and V6, but if it has large cut outs on the sides it's the same, if it has the narrow cutouts it's the GT manual style. There are only two types however, one with the narrow cutouts and one with the large cutouts.

My intuition says only the GT manual has the unique type, possibly a different drive shaft. I still need to do the IRS Diff swap write up for home mechanics as there really isn't any good ones on the net for S550 mustangs. Maybe I'll get motivated and do that tonight with lots of big fun photos....

https://performanceparts.ford.com/part/M-4851-M8A

and https://performanceparts.ford.com/download/instructionsheets/FordInstShtM-4851-M8A.pdf

I have not flashed it yet, I asked LMS about it and they pointed me to a $235 ford oem programmer module for making calibrations, the dealer (which I called and they said they didn't know if they could do that) or the pro-cal / sct / cobb aka any tuner (their system is an PCM flasher / code reader only).

I'm still not 100% sure if it even needs done, the cruise control is dead nutz on. My GPS records the same speed I set my cruise to. The Speed is pretty darn close, it reads within 1-2 mph at most of the GPS and cruise (the fat needle isn't super precise for determining speed to that accuracy anyway unlike my certified speedo in the 9C1 police impala I had during college).

So I'm really starting to wonder if I even need to have any cal done. Perhaps the speedo reads via axel rotation (aka wheel sensors) rather than via trans gearing? If it reads via axel speed then no cal would be needed, if it reads via trans speed then a cal is in order but I"m starting to think it's unnecessary.

Subbed because good information and because race car.

 

[speedfrk]

Not exactly. I ended up swapping the EB pinion flange to the GT diff, bought 3 pinion flange nuts (only $3 each from the dealer) just in case I needed to take it off or swap back to the stock diff. You can order the pinion flange for $75 but the dealer messed up the order and gave me the drive shaft coupler instead...so I had to re-use the stock pinion flange.

The EB and V6 manual pinion flange is the same as the GT automatic pinion flange interestingly enough. I'm not sure about the automatic EB and V6, but if it has large cut outs on the sides it's the same, if it has the narrow cutouts it's the GT manual style. There are only two types however, one with the narrow cutouts and one with the large cutouts.

My intuition says only the GT manual has the unique type, possibly a different drive shaft. I still need to do the IRS Diff swap write up for home mechanics as there really isn't any good ones on the net for S550 mustangs. Maybe I'll get motivated and do that tonight with lots of big fun photos....

https://performanceparts.ford.com/part/M-4851-M8A

and https://performanceparts.ford.com/download/instructionsheets/FordInstShtM-4851-M8A.pdf

Yep, I'd like to see the swap tutorial. I have a EB auto with 3:15 rear and I found a 3:73 local that I can get for about 800.00, although it might make 1st gear pretty useless with the automatic since it is already quite low. Maybe a 3:55 would be a better choice like the PP has.

 

[TheLion]

Yep, I'd like to see the swap tutorial. I have a EB auto with 3:15 rear and I found a 3:73 local that I can get for about 800.00, although it might make 1st gear pretty useless with the automatic since it is already quite low. Maybe a 3:55 would be a better choice like the PP has.

Given the higher ratio of the transmission combined with slip in the lower gears (typically torque converters hit about 90% unless you torque lock them) a 3.73 might be ok.

But I'd expect in the auto for your fuel economy to really take a dive going from 3.15 to 3.73 as that's quite a jump, but then again if you drive mostly city maybe it will go up slightly.

Unfortunately I didn't get time last night to do the tutorial, but I think I will today as I have to pick up my son after school, so I'll have a bit of free time. We'll see if I'm motivated enough :-)

I'm surprised no one has written a tutorial on this yet, the few that have done swaps seem to all be shops and well, they make their money by knowing and having the equipment and expertise to do stuff that some of us would shy away from (and for good reason). This I don't think is one of those things however as the only real specialty tool I needed was a torque dial for checking the bearing pre-load after torquing down a new pinion flange nut.

Mine was a bit tricky to measure. First the dial I used was borrowed from work, while it's caled every year, it was old and well abused, so every now and then the needle would just stay put and not move which made me question the last measurement...then my particular ring and pinion had a few spots which were a bit tighter than others, so some times the pre-load was 7~10 in-lbs to get it moving and other times it was 20~24 in-lbs.

Now the spec for used bearings is 8-14 and 16-32 for new bearings, so I figured that's as good as it was going to get, either way it was within either of the specs. Generally when talking about bearing pre-load or torque specs, it's important to use an instrument so you know your in the region, but it's not necessarily required to be spot on. Usually when it comes to torque specs within %5~%10 of the target is good enough unless it's an ultra high precision application like on a mechanical measuring instrument (aka something like the torque dial).

 

[speedfrk]

Yeah, the 3:15 is a bad match for an automatic EB. It lugs the engine down in almost all gears- Not unusual to be going 45mph at 1200rpm in 6th. I'm always hitting the paddle shifter down. Why Ford did this is absurd since it makes the car feel like a cheap economy car with the engine shuddering, etc.
Can you swap the diff without removing the entire subframe?

 

[5.0yote]

Yeah, the 3:15 is a bad match for an automatic EB. It lugs the engine down in almost all gears- Not unusual to be going 45mph at 1200rpm in 6th. I'm always hitting the paddle shifter down. Why Ford did this is absurd since it makes the car feel like a cheap economy car with the engine shuddering, etc.
Can you swap the diff without removing the entire subframe?

From the technical docs for the 6R80 I would venture to say 3.55s are the way to go that will give you a good bump in lower gearing without sacrificing mileage its a good happy medium but with enough improvement to make it worthwhile. I drove a PP comp orange EBM auto and it was just right in my opinion. Too low a gearing like 3.73s or higher may net you great launches but highway RPMS in an EBM will get annoyingly drony I think.

 

[ElAviator72]

3.31's are standard on the GT.

Not sure why a few people in this thread are making it plural...unless you're 4x4, there's only one differential in the car :lol:

 

[ElAviator72]

One thing I'm curious about, though, is the difference in technology. How is the Ecoboost's "Standard" limited-slip diff different from the Torsen that the GT's have?

 

[TheLion]

One thing I'm curious about, though, is the difference in technology. How is the Ecoboost's "Standard" limited-slip diff different from the Torsen that the GT's have?

The Torsen uses planetary worm gears, basically the worm gears are not fixed inside the casing, their shafts are on a slot rather than a hole. So as the differential unloads the worm gears are aloud to press harder against the casing walls (when you load any angled gear, it generates forces that push it aware from the mating gear, which loads the shaft / bearing it rotates on). Combine that with the friction from them still meshing against the center shaft gears (sun gears, they are not aloud to slip out of place, only move enough to apply pressure against the case wall), you have a marked increase in friction which results in the "limited slip" action. This is also why "friction modifiers" have a negative impact on the Torsen type diffs. They reduce the biasing ability by allowing more slip (aka reducing friction), so under light load conditions (like turning a sharp corner at an intersection while under normal throttle, they will slip continusously instead of stick / slip / stick / slip, which creates a noise smilar to a tire rubbing in the fender well). Albeit they still have plenty of biasing for actual performance driving.

The particular T2 variant that is specific only to Ford can bias up to 4:1 (standard T2's bias around 2:1 up to 3:1), so if your putting down 500 ft-lbs to the wheels (makes a nice example), the T2 can ideally transfer UP TO 400 of those to the non-slipping wheel while the other 100 will still be transferred up to the slipping wheel.

It self biases, so the more one wheel starts to loose traction the more torque is transferred tot he other wheel.

Also, when your not slipping either tire, you want an "open diff", so your not creating resistance to turning due to the difference in speed between the outer and inner tire (aka it affects turning radius, tire wear, traction and power to the wheels) all to varying degrees. The standard diffs also tend to wear out faster, requiring a re-build with new Z spring. They are a cheap alternative to an open diff, while better overall than an open diff, they are far from ideal.

The "traction lock" diff Ford has that essentially is another variation but more limted in it's ability, it actually locks up during high RPM if I'm not mistaken, but is an open diff at lower RPM (or it could be it locks up once you start to slip a certain amount, I don't recall). It's basically either open or posi, not limited slip. I think the traction lok is the standard type in the EB's and V6 (all flavors) and in non PP GT's. The Torsen is also only available as a factory option for the GT PP and probably also higher end variants like the GT350 and GT500's or an after market upgrade for any S550.

I think for drag racing and street the T-LOK's are just fine. For autocross or circuit tracks the T2 is a quite drastic improvement of you want to put any meaningful power down. Also for poor weather the T2 will help you get going better, especially if one tire is on iced over pavement while the other is on dry pavement (which happens frequently here in ohio during bad weather) as it will bias as much as is needed linearly as opposed to locking up into posi, which may cause you to break traction on the opposing wheel.

You can buy the Torsen as an aftermarket upgrade by itself from Ford Performance: http://www.americanmuscle.com/frpp-34spline-88-irs-torsen-diff-1516.html

or as a complete loaded housing (But you will need the Automatic Pinion Flange, which is used on all S550 EXCEPT the GT Manual (both PP and non PP): http://www.americanmuscle.com/frpp-irs-373-loaded-torsen-diff-1516.html

Traction LOK: http://www.americanmuscle.com/frpp-34spline-88-irs-diff-2015gt.html

Now I bought the Loaded GT PP diff, so it was already assembled with 3.73 ring and pinion and a Torsen. If you tear the diff apart you WILL need a case spreader, not easy to come buy. You could fabricate your own with some creativity. I didn't want to mess with all the shimming and gasket making etc inside housing. So I just swapped the pinion flange from my EB to the loaded GT PP diff as opposed to buying the T2 and 3.73 gears to put into my stock housing.

I also bought the loaded GT PP diff used from a scrap yard for $650. It's $1900 new...mine had only 10k and was donated at a discount from one very poor GT driver

 

[TheLion]

Here's some Eye candy:

The whole shebang coming out of the car (yes I actually balanced that 500~750lb sub assembly on a single jack...with a little carpentry and care it can be done ye home mechanics)


Removing the Pinion Flange Nut with a home made pinion flange nut tool (aka some steel channel I got at Home Depot and some M8 bolts and nuts)


Pinion Flange (from my EB diff) and Staked Pinion Flange Nut ($3.75 new from dealer, got 3 just in case) on the loaded GT PP diff


And the loaded diff now going back in the IRS frame (also did the diff bushings with steeda Black and the steeda aluminum IRS bushing supports)

 

[TheLion]

No the speedometer gets its input now from the ABS speed sensor, not the transmission. They are unrelated. Do not quote me on this part, but unless the transmission is getting speed data from the same source then it should be auto adjusting on its on within reason, I would not imagine they would put that type of control in the hands of just an ABS module to help the AT regulate gears, shifts etc. I think its just the speedo and cruise.

This is just related to vehicle speed info for your dash.

I suspect it (the 6R80 AT) still has its own speed sensor.

I believe your correct, so you would need to flash with an AT, but not with an MT. I checked it today carefully at several speeds, as far as my eyes can tell the speedo is in sync with the cruise which both also match up with my repoted GPS speed.

The GPS is pretty accurate, it was always spot on with my certified 9C1 Police Imapala speedo I had as my college car (yah the GPS is about 5 years old, but was top of the line at the time and still works great).

I'm not sure if the odometer is off however, but I would think the odo would go by the ABS speed sensors (there's one in each of the 4 wheels) as the only error then is in the sensor and any variations in tire roll out.

But it would still be nice to have an official source confirmation.

 

[TheLion]

For autocross, there are two things to remember - gear change takes you out of street class and on a faster courses you'll max out in 2nd gear very quickly - at least on a GT.

I don't think that applies if it's a factory option. 3.73 is a factory option for GT and I'm sure you could special order an EB with 3.73 for an up-charge.

 

[kz]

I don't think that applies if it's a factory option. 3.73 is a factory option for GT and I'm sure you could special order an EB with 3.73 for an up-charge.

Wrong. You could not. Neither GT PP guys stuck with 3.73 can install any other gear and stay street legal.
Also not that if the option came in a package, you have to install _entire_ package to stay legal - so somebody with non-PP GT wanting 3.73 (for whatever reason - as I said - most would love to go lower as max speed in 2nd gear is generally too low) would have to install entire PP (which is near impossible and certainly cost prohibitive) to stay compliant.
Even strut tower brace install on a car that came without isn't legal. I've been through this.

In your case - looking at the footer - with that many mods - it really doesn't matter at all.

 

[5.0yote]

I'm not sure if the odometer is off however, but I would think the odo would go by the ABS speed sensors (there's one in each of the 4 wheels) as the only error then is in the sensor and any variations in tire roll out.

But it would still be nice to have an official source confirmation.

It does use the ABS to get its readings, its the whole reason for that whipple ABS BCM flash unit. It seems to be that you would have to go very extreme to get out of the min max range that the system is capable of adjusting on its own.

I thought my speedo was off but what I found that while it looks 1-2 mph off if you look at it dead on (which we cant while driving as its offset to the right), you should note its pretty much on target. Even if it was 1-5MPH off its not enough off to make a difference in every day driving. I found setting the cruise control to your desired speed and confirming what cruise is set at on the dash to your GPS pretty much tells you if your dead on.

Mines fine. I like this setup better than having to keep reflashing your PCM for gears and tires when your outside the normal height/ratios.

I think once you get over say 27" tall tires and over 4.10s+ you may find the need to flash.

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