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GT40 Tech - Powertrain/Transaxles Transaxles and driveline - don't dare post engine things here!

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Old 25th January 2017, 03:28 PM   #1
Cliffbeer2
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Torsen v. LSD

Now I know this has been debated before, I'm just wondering now if anyone here has experience with a GT40 using a torsen diff on the track.

I have the opportunity to install either a porsche LSD or a torsen diff in my Fortus (Lotus Esprit with a SBF) audi 016 transaxle. I have the porsche LSD and have used them before in my old CAV and it was a huge improvement - eliminated torque steer (which there was quite a bit of) and made the car track straigther and be more much predictable in the curves where traction was compromised or lost.

I'm wondering how a torsen diff might compare, particularly in a track setting. Anyone know first hand?

Thanks in advance
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Old 26th January 2017, 11:02 AM   #2
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Frank833
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Re: Torsen v. LSD

No experience with one in GT40. But have had a torsen diff. My experience is that they take a bit of care car when cold (near freezing), as between the diff and cold tires, it is real easy to embarrass yourself. But even when cold, it you just give it a few minutes to warm up all is good.

Other than that, it is a much better diff all around. With ample horsepower the car went down the straights like a spooled rear, but was well behaved in the corners on the brakes or with light throttle. Heavy throttle and you are steering the car with the rear (I can tell you that does not work well with my SLC). I also found that there seemed to be no real difference in operation between a diff with 100 miles on it and one with 20,000 miles on it.

I am working on a new transaxle for the SLC and purchased a torsen style diff for it.
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Old 26th January 2017, 11:43 AM   #3
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Re: Torsen v. LSD

A few bullet points on advantages of a clutch pack LSD verses a Torsen style.
Clutch pack diffs are stronger, and tune-able. A nice feature especially in a Porsche is the you can configure the ramps to give you 100% lock up on decel. This is great on keeping the car straighter under heavy braking, not as critical on a mid-engine application. They are better in a track application if you are jumping curbs in corners as they still transfer torque with a wheel in the air. Much more tolerant of fat tire burnouts. Downside is the typical unit has a clutch pack preload which has to be overcome before it will differentiate. This can cause understeer and corner entry twitchiness,

A Torsen / ATB diff works perfectly on equal flat surfaces. Does not have the issues with preload turn in since there is an instant linear differentiation once you start to turn in. You will get a loss of drive if you get a one wheel launch off a curb and they can get tricky when you put a wheel on the grass or gravel when power on. I have seen several brands in bits because of drifting and too many burnouts. Not saying you can't split the gears in a clutch pack LSD but at least they stay contained in the diff housing. When you pop a Torsen sometimes the chunks find their way into the ring and pinion mess. As you can imagine that will be a lot more than a diff replacement, usually takes out the case and R&P too.

Taking the above into account, if the car is to be mostly street use, I would use a Torsen. Much better for slow speed turn in. For those using a Porsche G50 and perhaps one with some miles on the LSD diff, you will need to upgrade the internals since the stock friction plates / steels are shit. There are great internal plate pack upgrades available from the aftermarket. Better the new OEM. Nest step up after that is a complete Torsen or Clutch Pack LSD from the aftermarket.
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Old 27th February 2017, 03:21 PM   #4
Erik Johnson
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Re: Torsen v. LSD

I would say that it would depend on your HP and how you intend to drive the car.

I personally recommend the plate type differentials more often than not, but honestly speaking, if you are just looking for a bit more grip and you never really jump on the car, then in all probability a TBD will work just fine for you.

There are advantages to each option.

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Old 27th February 2017, 03:36 PM   #5
Cliffbeer2
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Re: Torsen v. LSD

Thank you fellas, this is great information. Very helpful.

I guess not surprisingly, the answer depends on usage profile and a few variables. Basically, this particular car will get driven on the street mostly, with the occasional track day with one of the clubs (probably Lotus, but would be fun to run with the Mustang club). I'm pretty civilized on the track, usually not jumping curbs, bit of sliding fun in the corners then hard on it down the straight.

The engine and transaxle is in the process of being installed....with the plate style LSD. I bought the torsen diff available for the 016 and will probably give that a try when the engine and transaxle next come out for an upgrade (better ratios, EFI, etc.)

Thanks again.
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Old 2nd March 2017, 03:14 AM   #6
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Re: Torsen v. LSD

I have had 2 TB diffs in my 40 ,I track and street.
The first one I found I could not run a rear sway bar as it caused an issue in harder corners if the inside wheel got light.
With the rear bar off it allowed the inside wheel to go into droop and get the grip.

As it turned out I didnt need the rear bar and it was great.
I know have a wavetrac feels about the same,I could run a rear bar if needed because it has a lock function if a wheel gets light.

The car is very good under brakes but I have not had a LSD in the car so I cant compare but I like the TB, I have not found a corner that it does not get grip.

Wavetrac do an LSD as well.

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Old 16th March 2017, 08:28 AM   #7
200MPH
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Re: Torsen v. LSD

Have run a quaife ATB diff in my 016/Porsche 944 hybrid trans since 2009. 11 000 km now and most of that is drive to track, compete, drive home. Love it. Totally smooth and seamless in operation. This is behind a strong 347 donk.
You shouldn't be kerb hopping a mid engined car and getting rear inside wheel off the deck, so I can't see any disadvantages in a torsen design.
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Old 26th March 2017, 09:23 PM   #8
advancedautomotion
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Re: Torsen v. LSD

Quote:
Originally Posted by 200MPH View Post
Have run a quaife ATB diff in my 016/Porsche 944 hybrid trans since 2009. 11 000 km now and most of that is drive to track, compete, drive home. Love it. Totally smooth and seamless in operation. This is behind a strong 347 donk.
You shouldn't be kerb hopping a mid engined car and getting rear inside wheel off the deck, so I can't see any disadvantages in a torsen design.
The only disadvantage is if a wheel is hiked up in the air, the Torsen behaves like an open diff. The exception is the wavetrac unit that is a hybrid Torque biasing diff and clutch type diff.
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