S197 Torsen choices

[Tim.ocon]

Very much considering a a Torsen upgrade and fingers crossed I can find one used (unless that’s a bad idea)
Is there any real difference between 8.8 Torsen diffs or are they all very similar, any specific ones I should avoid

Also having one HELL of a time finding any in Canada so any insight on the best way to ship one here from the states without paying obscene customs and duty is also appreciated or just what customs and duty may cost

 

[mwjscn]

M-4204-T31 - Old regular T2 design with 2:1 bias. I don't think this is anyone's first pick these days.
M-4204-T31H - T2R design with high bias of 4:1. Stock in the FR500S and good for tight cornering due to the higher bias.
M-4204-MB - Boss-specific with bias of 2.7:1. Regular Ford PN is CR3Z-4026-A, Torsen PN is 975420-0200AF. Torsen said this variant was designed to be a bit more robust over the older T2 designs to deal with the input torque from the Boss 302, likely since it was installed in a road car with a warranty. That being said, I think people are still throwing a lot at the T31H just fine.

Your choice mostly comes down to the bias ratio you'd like. For autocrossing, I think the ideal would be the 4:1 T31H whereas I think either that or MB version work fine in road course work. Limited Slip Additive isn't required, but you can add some to quiet it down a bit at the cost of up to 10% of your effective bias ratio. I got a Laguna Seca MB Torsen takeout with a 3.73 gearset that was lightly used (if I recall, around 20k miles) for $500 shipped, so deals can be found though I don't think they're as plentiful as before. You can check salvage yards for fresh Boss 302 or 2013-2014 Track Pack permanent visitors and see if they can extract and ship it to you if you want to try and find a used one, though usually they deal in whole-axle sales. All PNs are available new if it's within your budget.

Estimate duty and taxes

Canada Border Services Agency Duty and Taxes Estimator

www.cbsa-asfc.gc.ca

Duty is 0% whereas Tax is 15% on imported automotive parts to Nova Scotia it seems.

 

[Tim.ocon]

M-4204-T31 - Old regular T2 design with 2:1 bias. I don't think this is anyone's first pick these days.
M-4204-T31H - T2R design with high bias of 4:1. Stock in the FR500S and good for tight cornering due to the higher bias.
M-4204-MB - Boss-specific with bias of 2.7:1. Regular Ford PN is CR3Z-4026-A, Torsen PN is 975420-0200AF. Torsen said this variant was designed to be a bit more robust over the older T2 designs to deal with the input torque from the Boss 302, likely since it was installed in a road car with a warranty. That being said, I think people are still throwing a lot at the T31H just fine.

Your choice mostly comes down to the bias ratio you'd like. For autocrossing, I think the ideal would be the 4:1 T31H whereas I think either that or MB version work fine in road course work. Limited Slip Additive isn't required, but you can add some to quiet it down a bit at the cost of up to 10% of your effective bias ratio. I got a Laguna Seca MB Torsen takeout with a 3.73 gearset that was lightly used (if I recall, around 20k miles) for $500 shipped, so deals can be found though I don't think they're as plentiful as before. You can check salvage yards for fresh Boss 302 or 2013-2014 Track Pack permanent visitors and see if they can extract and ship it to you if you want to try and find a used one, though usually they deal in whole-axle sales. All PNs are available new if it's within your budget.

Estimate duty and taxes

Canada Border Services Agency Duty and Taxes Estimator

www.cbsa-asfc.gc.ca

Duty is 0% whereas Tax is 15% on imported automotive parts to Nova Scotia it seems.

I’m not familiar with the differences in biasing for these diffs. I’ll have to get the cliffs notes somewhere to make a educated decision

I see there is a T2 from a Shelby for sale in the classified that I had been considering but given what you are saying it may not be the best choice

I’m going to be doing a gear ratio swap (2.73 to 3.55) which is why I’ve been looking into the Torsen. Do it right or do it twice concept.

From the looks of what you have said the T2 doesn’t handle input torque as well as the others. Do you think this would be an issue for me with the v6 producing less input torque to start with, I don’t plan on doing anything crazy to increase power or engine torque

 

[mwjscn]

The simplest way to describe it is the differential has mechanical torque vectoring, with the ratio numerically describing how much vectoring it can provide to one side.
The '1' always refers to the inside tire in a corner and how much torque it can handle before spinning. The first number then refers to the ratio (multiplication) of torque that can be sent to the outside wheel. Since the outside wheel will always have more torque applied than the inside wheel when in correct operation, the result is 'steering' you around the corner.

Here are some examples with not-real numbers to just try to explain the operation:
T31 with a 2:1 bias, if the inside wheel can hold 50 ft-lbs of torque, up to 100 is sent to the outside wheel.
T31H with a 4:1 bias, if the inside wheel can hold 50 ft-lbs of torque, up to 200 is sent to the outside wheel.

Usually the traction limit is the inside wheel spin, hence why you see Torsen solid axle cars set up with a thin rear swaybar or none at all. If the tire spins or is lifted off the ground with a 4:1 biasing differential, 4 x 0 ft-lbs = 0 and the differential doesn't work as intended. Picking the bias ratio mostly comes down to the type of driving you're going to be doing, which the T2 might be fine at. There are a bunch of 'Ask Torsen' blog posts that may help you pick which one is best suited to your application, in addition to feedback from TMO.

Torsen® Traction

torsen.com

 

[racer47]

The T31H sells for almost $1000. The Eaton Truetrac costs $700 and has a 3.5 bias (if you have to buy new). I've had a Truetrac in 3 different cars over the years and they have always worked very well. I would never add friction modifier to any torsen. I use non synthetic 85w140.

EATON 913A561 Eaton Detroit Truetrac Differentials | Summit Racing

Free Shipping - Eaton Detroit Truetrac Differentials with qualifying orders of $109. Shop Differential Carriers at Summit Racing.

www.summitracing.com

https://lmr.com/item/M4204T31H/Ford-Racing-Mustang-Fr500s-T-2R-Torsen-Differential-86-14-M-

 

[TA28]

If your going to use the car on the street then the t31h boss 302/ shelby torsen is the 1 you want. The t2R high bias is a race unit .they were used in fr500c and fr500s race cars.

 

[Dave_W]

I'm not sure if it makes a difference for Canadian customs, but if you do buy used have the shipper use the word "used" in all the paperwork descriptions. I can't remember if it was for LTL truck freight or US customs, but I vaguely remember it made a difference in cost in some cases.

 

[Tim.ocon]

I'm not sure if it makes a difference for Canadian customs, but if you do buy used have the shipper use the word "used" in all the paperwork descriptions. I can't remember if it was for LTL truck freight or US customs, but I vaguely remember it made a difference in cost in some cases.

i believe this is correct as well

 

[Tim.ocon]

If your going to use the car on the street then the t31h boss 302/ shelby torsen is the 1 you want. The t2R high bias is a race unit .they were used in fr500c and fr500s race cars.

Is the T2R and the T31H not the same diff? Maybe I’m wrong but that’s what I’ve been reading

 

[Tim.ocon]

Okay. So from what I’m gathering higher bias ratio is better for on track but worse for the street.

I’m still wanting to drive it on the street but not as a daily driver so maybe something in the middle of the road between the T31 - T2 and T31H - T2R

What would be middle of the road? I’ve seen the Eaton truetrack mentioned aswell as the boss specific M-4204-MB and they both seem like good options

The M-4204-MB is $1180USD from ford performance where the eaton Truetrac is cheaper at about $700USD. Budget is obviously being taken into account but I don’t want to make a decision purely based on price

 

[TA28]

The eaton true trac and Detroit lockers are both great pieces. Both are more drag race friendly as ALL torsens are NOT!!! They will break. The torsen 2r is as I said race unit only . Ford/multimatic only installed it in fr500c then fr500s and boss 302 s/r.
I have t2r in my fr500c and a new eaton Detroit locker. The locker I have not used it yet. The t2r in a full race car I like it.
I soured on torsen units when I called them . They DO NOT service or repair there equipment nor do they sell replacement parts. So for 1100$ + it breaks its boat anchor! They are located in Rochester NY
Eaton on the other hand will repair and sells replacement parts.
Picture below is Detroit locker 4.30 gears cortex watts link 18mm rear sway bar roush bearing top link and aluminum heim jointed lower c/arms

 

[TA28]

Oh by the way the torsen listed 4sale here is mine. If you want more info on it .email me chris
[email protected]

 

[Tim.ocon]

Oh by the way the torsen listed 4sale here is mine. If you want more info on it .email me chris
[email protected]

View attachment 100092

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I think for the moment I’m okay. It’s the T2 from what the ad days and I think I’m going to go with the MB Torsen from the boss or gt500

Unless I’m getting confused and those are the same?
What year Shelby is that from

 

[TA28]

Torsen 2 I have for sale is from shelby boss car .they are same. It's out of 12 or 13 car I think.

 

[Tim.ocon]

Torsen 2 I have for sale is from shelby boss car .they are same. It's out of 12 or 13 car I think.

Aha
Okay then I may be in touch. @mwjscn found a full 2013 gt500 axel in Ontario with the Torsen so I just have to consider my options

Only reason I’m not 100% set on the full axel is because I’d still have to change the gear ratio because it’s only a 3.31 rather then a 3.55 I’m looking for so it may not be worth buying a full new axel to have to tear it apart anyway

Gotta do some thinking

 

[TA28]

I do have set of 3.55 gears out of boss 302s if interested they are from khor/ rehagen .they are rem polished.
I will add this I find it easier to swap hole rear as to pulling carrier and doing set up in the car.
I had 4 rear set ups with diff gear ratio for my fr500c. Chris

 

[Tim.ocon]

I do have set of 3.55 gears out of boss 302s if interested they are from khor/ rehagen .they are rem polished.
I will add this I find it easier to swap hole rear as to pulling carrier and doing set up in the car.
I had 4 rear set ups with diff gear ratio for my fr500c. Chris

Oh 100% I have no interest of swapping the gears and setting backlash on my back.

I have a set of 3.55s already from my dads 07 GT that he has graciously given me but I appreciate the offer

 

[stevbd]

Only reason I’m not 100% set on the full axel is because I’d still have to change the gear ratio because it’s only a 3.31 rather then a 3.55 I’m looking for so it may not be worth buying a full new axel to have to tear it apart anyway

I know it's less common but I run 3.31 with an Eaton Truetrac in my 2011 GT and love it. You'll have to do your own research on shift points for your tracks, corners, and V6 motor. But in my experience, with my car and on the tracks I drive, the 3.31 works well with small diameter 30 series track tires, you can hold gears longer and sometimes avoid unnecessary extra shifts which depending on the track and the corner can be an advantage. I haven't done a back to back comparison but I suspect I might actually be faster with the 3.31 because I'm not wasting time with extra shifts. Just something to think about.

If you can get a decent price on that full Shelby axle I think that is your ez button max-ROI solution for sure. I don't think you'll see a huge performance difference between 3.31 and 3.55 in any event, and being able to just swap in the whole axle would be a lot easier and cheaper. Just my random thoughts, good luck with the search.

 

[Dave_W]

a full 2013 gt500 axel

Note that the 2013-14 Torsen-equipped cars used a diffferent axle housing than all other S197 8.8-axle cars, internally machined to accommodate a larger bearing. They use rear pinion bearing 6L2Z-4625-AB instead of 9L3Z-4630-A. That's why many of the differential / R&P overhaul kits say "does not fit 2013-14 GT500." But in fact it's actually the 2013-14 GT500, 2013-only Torsen-only Boss 302, and 2013-14 Track Pkg. cars (I think all Track Pkg. came with Torsen). You can use those kits, but you have to buy the 6L2Z-4625-AB separately and toss the bearing in the kit. I've also read that axle is no longer available from Ford parts, partly due to Factory Five buying a bunch of them for use in their kits and Ford switching the production line over for the S550 IRS.

 

[Tim.ocon]

I know it's less common but I run 3.31 with an Eaton Truetrac in my 2011 GT and love it. You'll have to do your own research on shift points for your tracks, corners, and V6 motor. But in my experience, with my car and on the tracks I drive, the 3.31 works well with small diameter 30 series track tires, you can hold gears longer and sometimes avoid unnecessary extra shifts which depending on the track and the corner can be an advantage. I haven't done a back to back comparison but I suspect I might actually be faster with the 3.31 because I'm not wasting time with extra shifts. Just something to think about.

If you can get a decent price on that full Shelby axle I think that is your ez button max-ROI solution for sure. I don't think you'll see a huge performance difference between 3.31 and 3.55 in any event, and being able to just swap in the whole axle would be a lot easier and cheaper. Just my random thoughts, good luck with the search.

All of this is exactly my thought. I have to call the scrap yard today and check if the axel comes with the 13.8 inch rotor brackets. If it does then I’m 100% picking it up