Which Torsen?

[Sky Render]

Based on info I've read here and elsewhere, my stock track-lock differential is probably not long for this world. So I'm planning on saving money and upgrading it to a Torsen that can better handle the abuses of autocross and road courses.

The way a Torsen works is to send (or "bias") more power to the wheel that has more traction. The amount that is sent is known as the bias ratio. So, on a Torsen with a bias ratio of 4, 80% of the torque would be sent to the wheel with traction and 20% to the other wheel.

Keeping in mind that my car is my daily driver for about 10,000 miles a year or so, which Torsen should I get?

The track-pack cars come with a T-2 Torsen with a bias ratio of 2:
http://www.americanmuscle.com/ford-31spline-88-t2-diff.html

The Boss 302 Laguna Seca comes with a T-2 Torsen with a bias ratio of 2.7:
http://www.jpcracing.com/2012-mustang-boss-302-torsen-differential/

And the FR500s came with a T-2R Torsen with a bias ratio of 4 and a pre-loaded clutch:
http://www.americanmuscle.com/ford-31spline-88-fr500-diff.html

Keeping in mind that my car is driven on the street a lot, which Torsen would be best in terms of value, performance, longevity, and streetability?

 

[sheizasosay]

That FR500 one is the one I would pick.

 

[skwerl]

The Eaton TrueTrac is a similar design and has an excellent reputation for durability. They are also a bit less than the Torsen. I put mine in last year and if somebody didn't tell you, you'd never know it was there (except for the awesome traction). The TrueTrac is a 3-1 bias ratio I believe.

 

[Sky Render]

That FR500 one is the one I would pick.

May I ask why? I understand that a $200 price increase isn't that big of a deal when you're talking about a total installed cost of about $1,200 for the less-expensive T-2. However, I want to make sure that whatever diff I get will still be streetable.

The Eaton TrueTrac is a similar design and has an excellent reputation for durability. They are also a bit less than the Torsen. I put mine in last year and if somebody didn't tell you, you'd never know it was there (except for the awesome traction). The TrueTrac is a 3-1 bias ratio I believe.

Now, I didn't think about the Eaton/Detroit TrueTrac:
http://www.americanmuscle.com/eaton-31spline-88-posi-lsd.html

That's about $60 cheaper than the 2:1 Torsen T-2. Have you had any issues at all with yours? Is it noisy? How much do you drive it?

 

[skwerl]

I drive mine all the time and the TrueTrac makes no noise at all. It also holds up to drag racing and dumping the clutch at 5000rpm with slicks.

 

[Sky Render]

I heard those Eatons were pretty stout. Are they a good differential to use for corner-carving, though?

 

[Whiskey11]

I heard those Eatons were pretty stout. Are they a good differential to use for corner-carving, though?

The Bias ratio is lower than the T2R at 2.7 IIRC (same as the T2). A few I've talked to absolutely love it but they are also not serious autocrossers. The few I have talked to about the TruTrac mentioned that the bias ratio was too low and still allowed inside wheel spin in hard cornering.

 

[Sky Render]

The Bias ratio is lower than the T2R at 2.7 IIRC (same as the T2). A few I've talked to absolutely love it but they are also not serious autocrossers. The few I have talked to about the TruTrac mentioned that the bias ratio was too low and still allowed inside wheel spin in hard cornering.

The cheaper T-2 has a bias ratio of only 2, so the Truetrac would be a better buy in that case.

I just want to put something in there that's reliable so I can change the fluid once a year and be done with it.

 

[JesseW.]

I autox the truetrac in mine. Much better than the stock diff and won't explode like the torsens have been known to. Drivetrainamerica.com usually had the best prices.

 

[lito]

I've only used an old T2 28spline for autocrossing and the FR500 one in a FR500S in the track and I think the 2nd one feels better but use conditions were not the same, I would go with the higher ratio for autox, but that is me.

 

[Scruffy]

I'm no autocrosser, but curious how the Truetrac would work and hold up on the road course vs. the stock Ford diff.

 

[19COBRA93]

If I were to choose one of them, it would be the Boss/GT500 torsen. Simply because it's a more robust unit, although the most expensive too. It doesn't have the bias of the T2R, but I would pick durability/strength over the bias ratio any day.

I've had bad luck with a T2, and don't have a lot of faith in the Torsens personally because I drag race on occasion, in addition to autocross. But I really like the Boss unit, and would run it in my own car if it weren't so pricey.

I'm no autocrosser, but curious how the Truetrac would work and hold up on the road course vs. the stock Ford diff.

I can tell you the Trutrac is a world above the stock ford diff (as would be any of the worm gear diffs). It's actually quite amazing how different, and how much better it performs. My car is just straight planted now when I lay into the throttle, Especially around a corner. And even when it spins, it's fighting for grip constantly. Before with the stock diff it would just spin and hit the limiter. I'd have to let out, or shift. Now, if it spins, it's still accelerating and putting power where it needs to go.

 

[Sky Render]

Huh, you guys are making me seriously consider that Eaton...

 

[Department Of Boost]

My blue car has had a T2R in it for a little over 10K VERY hard miles. Lots of power, lots of traction, I’m constantly doing burnouts and “drifting” through corners. I haven’t had one problem with it.

Its also silent. And under normal driving you wouldn't even know it was there.

And it works GREAT! It feels like there is a little dude back there directing traffic. Its great.

 

[Sam Strano]

The good old internet. Some of the information here is right, some isn't. There are no clutches in a T2R, or in fact any Torsen... and I don't care what you read, or where it's not true.

I have my preference, and when it's to get power down, you want a diff that can bias power. Hell, there is a pretty common small car that has a 4:1 Torsen in it now, stock.

 

[19COBRA93]

Its also silent. And under normal driving you wouldn't even know it was there.

And it works GREAT! It feels like there is a little dude back there directing traffic. Its great.

I've felt that way with all the gear diffs I've driven on. They're all dead quiet, and it really feels like there's someone back there commanding power to the correct tire. Probably more so with the T2R or even Wavetrac with their high bias.

 

[19COBRA93]

The good old internet. Some of the information here is right, some isn't. There are no clutches in a T2R, or in fact any Torsen... and I don't care what you read, or where it's not true.

I have my preference, and when it's to get power down, you want a diff that can bias power. Hell, there is a pretty common small car that has a 4:1 Torsen in it now, stock.

Actually the T2R has friction plates.

They're even mentioned right on Torsens webpage:

http://www.torsen.com/products/T-2R.htm

I'm really curious why you say they don't? That's a serious question actually, because I've always understood that they do, and all the information I"m finding says they do, but if that's incorrect, please let us know.

 

[lostsoul]

I love my truetrack(burned up the stock long ago).. had it for about 3-4 years, now if I can only learn to shift right =-/

 

[Vorshlag-Fair]

I've used a lot of different diffs in a lot of different cars over the past 25 years of racing and my two favorites were an OS Giken in one of my BMWs ($1600 diff!) and the T-2R we just put in our 2011 Mustang. These both had none of the bad characteristics of a heavy, clutch style diff. I'll copy a bit from my last build thread update, where I covered the T-2R. I haven't tried the Tru-Trac but we are going to use this in an F-body soon - they are SO cheap, and do work in similar ways.


====copying from our build thread=====

Torsen T-2R Differential Upgrade

With the rearend housing back in the car (no, it wasn't weighed - we forgot, by damn!) it was re-attached to the various control arms and the swaybar was reinstalled with the new Whiteline brackets. Now it was time to install the new Torsen T-2R differential with the original 3.31:1 gearset, as the rebuilt TractionLok LSD wasn't lasting 2-3 track days with the current power level and high grip tires, even with the carbon clutch disc upgrade.



The Torsen LSD design doesn't use any internal clutches. Therefore it doesn't have some of the negative handling interactions that a clutch-style differential has from somewhat locking the inside and outside wheels together under all circumstances (push on corner entry, loose on corner exit), but it doesn't work if one of the driven tires becomes airborne. How it works is more complicated - it involves worm gears, thrust forces and... some form of black magic. Read the links below to learn more:

• Torsen FAQ : http://www.torsen.com/general/general_faq.htm
• And some on the T-2R: http://www.torsen.com/products/T-2R.htm

One thing to note was that the Torsen units (both the T-2 and T-2R we purchased for this and another project) weigh a solid 5 pounds more than the OEM diff. If you see them side by side (middle pic above) you can see why, as the Torsen is full of worm gears and not an "S-spring" and a bunch of air in the middle. Our guys set-up the gears, backlash and installed new bearings on the Torsen and the old 3.31 gearset. It went in and works very quietly, with only some normal "Torsen noise" in a tight parking lot turn.

=====end of copied text=====

Now I haven't used this one at autocross speeds yet but we did have an uber-tight 2nd gear corner at our last NASA TT event (Turn "8" in the graphic above). This corner was slow, had a huge elevation change over about 100 feet of track, and was a full lock turn, unusual for most road courses. I've driven this in 4 different cars and each one fought for traction all the way up the hill out of turn 8 towards turn 9.

Only other track we've driven in this 2011 GT where I had to use 2nd gear and was this tight was the corkscrew at Harris Hill (similar to LEguna Seca's turn of the same name). Always fought for traction in the Mustang there, too. Well, with the T-2R it was hooked up. While some of the other TT cars were billowing smoke off the inside tire this Mustang was clawing it's way around the corner and up the hill.

I am a Torsen believer. And I also agree that if you are going to do the swap, and you autocross or track your car, go ahead get the 4:1 ratio T-2R. I know a lot of road racers and autocrossers with F-body and Mustangs who all swear by the T-2R. It is the sh!t.

Actually there is another track where I would like to try to use 2nd gear in a corner - Turn 11 at Eagles Canyon Raceway, shown above. I'm always lighting up the inside tire and fighting oversteer here in 2nd gear so I've been using 3rd gear anymore, even on 315mm A6 Hoosiers. If I use 2nd gear it always ends up sideways, like the picture above, and it is obviously slower. But now that we have the T-2R LSD in the car maybe it will finally hook up in that corner, using 2nd. 3rd gear always bogs down a bit and feels slow. Next time we run ECR I'll try second. Hey, that's in two days. I will report back how that goes.

Note: as for the T-2R having clutches, well, I've read that it does and read that it doesn't. Even that Torsen T-2R page (linked above and in my post) has some contradictory information about the clutches/preload. You can't see any of the clutches when looking closely inside a T-2R, which we did here, but we didn't disassemble the unit (and I would discourage you from doing that). I don't really care... it works like a Torsen and doesn't cause the normal "push at turn in/loose at corner exit" that a tightly pre-loaded clutch style diff does.

Just my two cents.

 

[Sky Render]

Thanks for the input, Terry. Do you think the T-2R would still be good for a lot of street use? I did some reading over on Corner Carvers and read a lot of good things about the Eaton Truetrack. I'll be honest--I'm also leaning in that direction due to cost reasons and the fact that I do drag race every so often.

The good old internet. Some of the information here is right, some isn't. There are no clutches in a T2R, or in fact any Torsen... and I don't care what you read, or where it's not true.

I have my preference, and when it's to get power down, you want a diff that can bias power. Hell, there is a pretty common small car that has a 4:1 Torsen in it now, stock.

So are you actually going to contribute something constructive to this discussion?